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LuminosityPublicResults

Introduction

Here any results related to ATLAS luminosity measurements are given. For Run-2 results, please see Luminosity Results for Run-2 (2015-2018).

Publications and Conference Results

Luminosity:

Satellite Bunches:

Integrated luminosity summary plots for 2011-2012 data taking

These plots show the estimated integrated luminosity with the most recent offline calibration, including also the integrated luminosity after good data quality requirement. (September 2013)

Total Integrated Luminosity in 2011
Cumulative luminosity versus time delivered to (green), and recorded by ATLAS (yellow) during stable beams and for pp collisions at 7 TeV centre-of-mass energy in 2011. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow a beam dump or beam studies. The recorded luminosity reflects the DAQ inefficiency, as well as the inefficiency of the so‐called "warm start": when the stable beam flag is raised, the tracking detectors undergo a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. Given is the luminosity as determined from counting rates measured by the luminosity detectors. These detectors have been calibrated with the use of the van-der-Meer beam-separation method, where the two beams are scanned against each other in the horizontal and vertical planes to measure their overlap function. The luminosity shown represents the 7 TeV luminosity calibration as published in Eur.Phys.J. C73 (2013) 2518.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011-2012/Luminosity/intlumivstime2011.png
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delivered only eps file
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Total Integrated Luminosity and Data Quality in 2011
Cumulative luminosity versus time delivered to (green), recorded by ATLAS (yellow), and certified to be good quality data (blue) during stable beams and for pp collisions at 7 TeV centre-of-mass energy in 2011. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow a beam dump or beam studies. The recorded luminosity reflects the DAQ inefficiency, as well as the inefficiency of the so‐ called "warm start": when the stable beam flag is raised, the tracking detectors undergo a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. The data quality assessment shown corresponds to the All Good efficiency shown in the 2011 DQ table. The AllGood data quality criteria requires all reconstructed physics objects to be of good data quality. Analysis relying only on a subset of physics objets may use a slightly larger integrated luminosity. The luminosity shown represents the 7 TeV luminosity calibration as published in Eur.Phys.J. C73 (2013) 2518. Data quality has been assessed after reprocessing.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011-2012/Luminosity/intlumivstime2011DQ.png
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Total Integrated Luminosity in 2012
Cumulative luminosity versus time delivered to (green), and recorded by ATLAS (yellow) during stable beams and for pp collisions at 8 TeV centre-of-mass energy in 2012. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow a beam dump or beam studies. The recorded luminosity reflects the DAQ inefficiency, as well as the inefficiency of the so‐called "warm start": when the stable beam flag is raised, the tracking detectors undergo a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. Given is the luminosity as determined from counting rates measured by the luminosity detectors. These detectors have been calibrated with the use of the van-der-Meer beam-separation method, where the two beams are scanned against each other in the horizontal and vertical planes to measure their overlap function. The luminosity shown represents the preliminary 8 TeV luminosity calibration.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011-2012/Luminosity/intlumivstime2012.png
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delivered only eps file
delivered only png file

Total Integrated Luminosity and Data Quality in 2012
Cumulative luminosity versus time delivered to (green), recorded by ATLAS (yellow), and certified to be good quality data (blue) during stable beams and for pp collisions at 8 TeV centre-of-mass energy in 2012. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow a beam dump or beam studies. The recorded luminosity reflects the DAQ inefficiency, as well as the inefficiency of the so‐ called "warm start": when the stable beam flag is raised, the tracking detectors undergo a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. The data quality assessment shown corresponds to the All Good efficiency shown in the 2012 DQ table. The luminosity shown represents the preliminary 8 TeV luminosity calibration. Data quality has been assessed after reprocessing.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011-2012/Luminosity/intlumivstime2012DQ.png
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Total Integrated Luminosity in 2011 and 2012
Cumulative luminosity versus time delivered to (green), and recorded by ATLAS (yellow) during stable beams and for pp collisions at 7 and 8 TeV centre-of-mass energy in 2011 and 2012. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow a beam dump or beam studies. The recorded luminosity reflects the DAQ inefficiency, as well as the inefficiency of the so‐ called "warm start": when the stable beam flag is raised, the tracking detectors undergo a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. Given is the luminosity as determined from counting rates measured by the luminosity detectors. These detectors have been calibrated with the use of the van-der-Meer beam-separation method, where the two beams are scanned against each other in the horizontal and vertical planes to measure their overlap function. The luminosity shown represents the 7 TeV luminosity calibration as published in Eur.Phys.J. C73 (2013) 2518, and the 8 TeV preliminary luminosity calibration.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011-2012/Luminosity/intlumivstime2011-2012.png
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delivered only eps file
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Total Integrated Luminosity and Data Quality in 2011 and 2012
Cumulative luminosity versus time delivered to (green), recorded by ATLAS (yellow), and certified to be good quality data (blue) during stable beams and for pp collisions at 7 and 8 TeV centre-of-mass energy in 2011 and 2012. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow a beam dump or beam studies. The recorded luminosity reflects the DAQ inefficiency, as well as the inefficiency of the so‐called "warm start": when the stable beam flag is raised, the tracking detectors undergo a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. The data quality assessment shown corresponds to the All Good efficiency shown in the 2011 and 2012 DQ tables. The luminosity shown represents the published 7 TeV and the preliminary 8 TeV luminosity calibration. Data quality has been assessed after reprocessing.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011-2012/Luminosity/intlumivstime2011-2012DQ.png
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Multiple Year Collision Plots

These plots are based on the online luminosity estimate.

Number of colliding bunches versus time
The number of colliding bunches in ATLAS versus time during the p-p runs of 2010,2011 and 2012.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/bunchesvstime.png
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Peak Luminosity versus time
The peak instantaneous luminosity delivered to ATLAS per day versus time during the p-p runs of 2010,2011 and 2012. The online luminosity measurement is used for this plot.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/lumivstime.png
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Peak pileup versus time
The maximum mean number of events per beam crossing versus day during the p-p runs of 2010,2011 and 2012. This version shows the average value for all bunch crossings in a lumi-block. The online luminosity measurement is used for this calculation as for the luminosity plots. Only the maximum value during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/muvstime.png
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Delivered Luminosity versus time for 2010,2011,2012 (p-p data only)
Cumulative luminosity versus day delivered to ATLAS during stable beams and for p-p collisions. This is shown for 2010 (green), 2011 (red) and 2012 (blue) running. The online luminosity is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/intlumivsyear.png
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logarithmic y-scale version
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Delivered Luminosity versus time for 2010,2011,2012 (including both p-p and Pb-Pb data)
Cumulative luminosity versus day delivered to ATLAS during stable beams and for p-p and Pb-Pb collisions. This is shown for 2010 (green for p-p, magenta for Pb-Pb), 2011 (red for p-p, turquoise for Pb-Pb) and 2012 (blue) running. The online luminosity is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/intlumivsyearHI.png
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Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2011 and 2012 data. This shows the full 2011 and 2012 pp runs. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing calculated for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 71.5 mb for 7TeV collisions and 73.0 mb for 8TeV collisions, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2011_2012-dec.png
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Annual plots

They are based on the online luminosity determination

2012 pp Collisions

Data Taking Efficiency and Pileup Interactions

Data Taking Efficiency per Day
ATLAS data taking efficiency in 2012. The denominator is the luminosity delivered between the declaration of stable beams and the LHC request to turn the sensitive detectors off to allow a beam dump or beam studies. The numerator is the luminosity recorded by ATLAS. Each bin represents a week. The empty bins are due to weeks in which no stable beams were delivered by the LHC. The inefficiency accounts for the turn-on of the high voltage of the Pixel, SCT and some of the muon detectors and any inefficiencies due to deadtime or due to individual problems with a given subdetector that prevent the ATLAS data taking to proceed.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/recEffByDay.png
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Data Taking Efficiency per Week
Same as above but per week.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/recEffByWeek.png
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Number of Interactions per Crossing
The maximum mean number of events per beam crossing versus day. This version shows the average value for all bunch crossings in a lumi-block. The online luminosity measurement is used for this calculation as for the luminosity plots. Only the maximum value during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/peakAvgMuByDay.png
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Number of Interactions per Crossing
The maximum mean number of events per beam crossing versus day. It is determined for each bunch as described above. The online luminosity measurement is used for this calculation as for the luminosity plots. In this plot both the maximum pileup for any bunch is shown in green, as well as the maximum pileup averaged over all the colliding bunches (shown in blue).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/peakBothMuByDay.png
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Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for 2012 (full pp collisions dataset). The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 73 mb, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2012-dec.png
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2011 pp Collisions

Data Taking Efficiency and Pileup Interactions

Data Taking Efficiency per Day
ATLAS data taking efficiency in 2011. The denominator is the luminosity delivered between the declaration of stable beams and the LHC request to turn the sensitive detectors off to allow a beam dump or beam studies. The numerator is the luminosity recorded by ATLAS. Each bin represents a week. The empty bins are due to weeks in which no stable beams were delivered by the LHC. The inefficiency accounts for the turn-on of the high voltage of the Pixel, SCT and some of the muon detectors and any inefficiencies due to deadtime or due to individual problems with a given subdetector that prevent the ATLAS data taking to proceed.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/recEffByDay.png
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Data Taking Efficiency per Week
Same as above but per week.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/recEffByWeek.png
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Number of Interactions per Crossing
The maximum mean number of events per beam crossing versus day. This version shows the average value for all bunch crossings in a lumi-block. The online luminosity measurement is used for this calculation as for the luminosity plots. Only the maximum value during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/peakAvgMuByDay.png
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Number of Interactions per Crossing
The maximum mean number of events per beam crossing versus day. It is determined for each bunch as described above. The online luminosity measurement is used for this calculation as for the luminosity plots. In this plot both the maximum pileup for any bunch is shown in green, as well as the maximum pileup averaged over all the colliding bunches (shown in blue).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/peakBothMuByDay.png
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Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for 2011. The plot is shown for data taken before and after the September Technical Stop where the beta* was reduced from 1.5m to 1.0m. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing. It is calculated from the instantaneous luminosity as μ=L x σinel / (nbunch x fr) where L is the instantaneous luminosity, σinel is the inelastic cross section which we take to be 71.5 mb, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185. The entries at μ~0 arise from pilot bunches that were present during many of the early LHC fills. The luminosity in these bunches is >100 times smaller than in the main bunches resulting in values μ<0.1.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/mu_2011-1.png
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2010 pp Collisions

Luminosity versus day

Total Integrated Luminosity
Online plot of the cumulative luminosity versus day delivered to (green), and recorded by ATLAS (yellow) during stable beams and for pp collisions at 7 TeV centre-of-mass energy. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to turn the sensitive detector off to allow a beam dump or beam studies. Given is the luminosity as determined from counting rates measured by the luminosity detectors. These detectors have been calibrated with the use of the van-der-Meer beam-separation method, where the two beams are scanned against each other in the horizontal and vertical planes to measure their overlap function. The systematic uncertainty of the luminosity measurement is estimated to be 3.4%, dominated by the uncertainty in the beam current product of 2.9%. The offline luminosity determined recently is 3.6% lower than the online luminosity shown here. The ratio of the recorded to delivered luminosity gives the ATLAS data taking efficiency (weighted by Luminosity) of 93.6%. The inefficiency accounts for the turn-on of the high voltage of the Pixel, SCT and some of the muon detectors (2.0%) and any inefficiencies due to deadtime or due to individual problems with a given subdetector that prevent the ATLAS data taking to proceed (4.4%). An additional 0.8 pb-1 of luminosity was delivered by the LHC between the request for ATLAS to turn off the sensitive detectors and the end of stable beam conditions.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/sumLumiByDay.png
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logarithmic y-scale version
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Integrated Luminosity per day
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/lumiByDay.png
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logarithmic y-scale version
logarithmic y-scale eps file
Peak Luminosity per day
The maximum instantaneous luminosity versus day delivered to ATLAS. The luminosity determination is the same as described above for the integrated luminosity. Only the peak luminosity during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/peakLumiByDay.png
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logarithmic y-scale version
logarithmic y-scale version eps file

Luminosity versus week

Total Integrated Luminosity
Cumulative luminosity versus week delivered to (green), and recorded by ATLAS (yellow) during stable beams and for 7 TeV centre-of-mass energy. The definition is identical to the daily luminosity plots above.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/sumLumiByWeek.png
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logarithmic y-scale version
logarithmic y-scale version eps file
Integrated Luminosity per week
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/lumiByWeek.png
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logarithmic y-scale version
logarithmic y-scale eps file
Peak Luminosity per week
The maximum instantaneous luminosity versus week delivered to ATLAS. The luminosity determination is the same as described above for the integrated luminosity. Only the peak luminosity during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/peakLumiByWeek.png
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logarithmic y-scale version
logarithmic y-scale version eps file

Data Taking Efficiency and Pileup Interactions

Data Taking Efficiency
ATLAS data taking efficiency in 2010. The denominator is the luminosity delivered between the declaration of stable beams and the LHC request to turn the sensitive detectors off to allow a beam dump or beam studies. The numerator is the luminosity recorded by ATLAS. Each bin represents a week. The empty bins are due to weeks in which no stable beams were delivered by the LHC. The efficiency integrated (and weighted by the weekly luminosity) over this data taking period is 93.6%. The inefficiency accounts for the turn-on of the high voltage of the Pixel, SCT and some of the muon detectors (2.0%) and any inefficiencies due to deadtime or due to individual problems with a given subdetector that prevent the ATLAS data taking to proceed (4.4%).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/recEffByWeek.png
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ATLAS Warm Start
When the stable beam flag is raised, some of the tracking and muon detectors undergo a so-called "warm start", which includes a ramp of the high-voltage and, for the pixel system, turning on the preamplifiers. Shown is the time this procedure took after declaring stable beams. The typical time is 5-10’. The occasional spikes are due to either caution e.g. when the background conditions have changed or due to DAQ problems during this procedure that prevented ATLAS going into this “READY” mode.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/readyTimeByFill.png
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Number of Interactions per Crossing
The average number of events per beam crossing at the start of an LHC fill versus day. The mean number of events per crossing is calculated from the per bunch luminosity assuming a total inelastic cross section of 71.5 mb. The online luminosity measurement is used for this calculation as for the luminosity plots. Only the maximum value during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/DataSummary/figs/peakMuByDay.png
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2013 p-Pb Collisions

Luminosity versus day

Total Integrated Luminosity in 2013 p-Pb run
Cumulative luminosity versus day delivered to (dark blue), and recorded by ATLAS (light blue) during stable beams and for p-Pb collisions at 5 TeV centre-of-mass energy in 2013. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to turn the sensitive detector off to allow a beam dump or beam studies. Given is the luminosity as determined online using counting rates measured by the luminosity detectors, and by assuming a total p-Pb nuclear cross section of 2.12 barn. The detection efficiency for the luminosity determination is obtained from Monte Carlo simulation.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2013hip/DataSummary/figs/sumLumiByDay.png
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2011 Pb-Pb (Heavy Ion) Collisions

Total Integrated Luminosity
Cumulative integrated luminosity versus day delivered to (dark blue), and recorded by ATLAS (light blue) for Heavy Ion (Pb) collisions during stable beams and for 2.76 TeV centre-of-mass energy per nucleon. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to turn the sensitive detector off to allow a beam dump or beam studies. Given is the luminosity as determined online using counting rates measured by the luminosity detectors, and by assuming a total Pb-Pb nuclear cross section of 7.65 barn. The detection efficiency for the luminosity determination is obtained from Monte Carlo simulation.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011hi/DataSummary/figs/sumLumiByDay.png
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Integrated Luminosity per day
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011hi/DataSummary/figs/lumiByDay.png
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Peak Luminosity per day
The maximum instantaneous luminosity versus day delivered to ATLAS. The luminosity determination is the same as described above for the integrated luminosity. Only the peak luminosity during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011hi/DataSummary/figs/peakLumiByDay.png
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2010 Pb-Pb (Heavy Ion) Collisions

Total Integrated Luminosity
Cumulative integrated luminosity versus day delivered to (dark blue), and recorded by ATLAS (light blue) for Heavy Ion (Pb) collisions during stable beams and for 2.76 TeV centre-of-mass energy per nucleon. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to turn the sensitive detector off to allow a beam dump or beam studies. Given is the luminosity as determined online using counting rates measured by the luminosity detectors, and by assuming a total Pb-Pb nuclear cross section of 7.65 barn. The detection efficiency of 79%, for the current method used, is obtained from Monte Carlo simulation.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010hi/DataSummary/figs/sumLumiByDay.png
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Integrated Luminosity per day
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010hi/DataSummary/figs/lumiByDay.png
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Peak Luminosity per day
The maximum instantaneous luminosity versus day delivered to ATLAS. The luminosity determination is the same as described above for the integrated luminosity. Only the peak luminosity during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010hi/DataSummary/figs/peakLumiByDay.png
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Detailed Additional Luminosity related Information

2011 Luminosity Calibration

Specific Luminosity during vdM scan
Comparison of the absolute specific luminosity measured by BCM and LUCID in beamseparation scans VII and VIII in May 2011. The top plot shows the specific luminosity inferred, for each of the 14 colliding bunches, from the measured bunch intensities and the transverse convolved beam sizes determined using either the BCM_EventOR or the LUCID_EventOR luminosity algorithm (the statistical error bars are smaller than the symbols). The bottom plot displays the corresponding results using the BCM_EventAND and LUCID_EventAND algorithms.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/ORLspecVsLUCID.jpg
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/ANDLspecVsLUCID.jpg
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Specific Luminosity during vdM scan
Comparison of the absolute specific luminosity measured by BCM and LUCID in beamseparation scans VII and VIII in May 2011. The top plot shows the specific luminosity inferred, for each of the 14 colliding bunches, from the measured bunch intensities and the transverse convolved beam sizes determined using either the BCM_EventOR or the LUCID_EventOR luminosity algorithm (the statistical error bars are smaller than the symbols) from scan VII . The bottom plot displays the corresponding results for scan VIII.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/ORLspecVsLUCIDVII.jpg
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/ORLspecVsLUCIDVIII.jpg
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time stability of luminosity calibration
The ratio of the integrated luminosity from different measurements with respect to the BCMH_ EventOR luminosity, obtained using different luminosity detectors and as a function of time. Each point shows the deviation for a single ATLAS run, averaged over all colliding bunches and over the duration of that run. The statistical uncertainties per point are negligible. The absolute scales of the TILE and FCal luminosity measurements were each pegged to that of BCMH_EventOR in May 2011 (run 182161, fill 1787). The absolute luminosity calibrations of the LUCID and BCM algorithms are those derived from the May 2011 van der Meer scans. Top: TILE and Forward calorimeters. Middle: TILE, FCal and BCM-V. Bottom: TILE, FCal, BCM-V and LUCID.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/timeStability.jpg
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/timeStability2.jpg
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/timeStability3.jpg
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μ-dependence of luminosity calibration
Fractional deviation in the value of μ (the mean number of inelastic pp collisions per bunch crossing) with respect to the BCM-H_EventOR luminosity algorithm, obtained using different luminosity detectors, as a function of the μ-value measured by the BCM-H detector averaged over all colliding bunches in each ATLAS run. Each point shows the deviation averaged over 20 runs in 2011. The statistical uncertainties per point are negligible. The absolute scales of the TILE and FCal luminosity measurements were each pegged to that of BCMH_EventOR in May 2011 (run 182161, fill 1787). The absolute luminosity calibrations of the LUCID and BCM algorithms are those derived from the May 2011 van der Meer scans.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/muConsistency.jpg
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"Afterglow" background for LUCID and BCM
The black points show the luminosity measured by the LUCID and BCM detectors for individual colliding bunch pairs (the measurement of the two detectors are indistinguishable on this scale). The red and blue points show the luminosity calculated from signals in the slots into which no bunches were injected; they give a measure of the level of the so-called afterglow background. Only a quarter of all available bunch slots (800 out of 3500) are displayed here, for the sake of clarity. The gaps between bunch trains (around bunch numbers 400, 780, 980, 1180) and between minitrains (around bunch numbers 530, 610, 680,...) reflect the details of the filling scheme used in this particular run.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/afterglow.jpg
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μ-dependence during the vdM scan
Fractional deviation in the value of μ (the mean number of inelastic pp collisions per bunch crossing) with respect to the BCM-H_EventOR luminosity algorithm, obtained using different luminosity detectors and as a function of the μ-value measured by the BCM-H detector during the May 2011 van der Meer scans. The high-μ values correspond to the beams being well centered on each other in the transverse plane, while the degraded statistical accuracy at low μreflects the increased relative transverse separation between the two beams during the luminosity-calibration scans.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/vdMMuPlot.jpg
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Luminosity Plots for Specific LHC Fills

ATLAS instantaneous luminosity
ATLAS instantaneous luminosity profiles as measured online for representative LHC fills with 7 TeV centre-of-mass energy in 2010. The gray shaded curves give the delivered luminosity, the green shaded curves show the delivered luminosity during stable beam conditions allowing ATLAS to turn on their tracking devices, and the yellow shaded curves give the recorded luminosity with the entire detector available. The missing recording at around 10:00 during Fill 1104 was caused by an intermediate removal of the stable beams condition flag by the LHC.

The luminosity values shown have been calibrated with van-der-Meer beam-separation scan data. The error on the luminosity is estimated to be 11%, dominated by the uncertainty in the beam intensities.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumi1298.png eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumi1225.png eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumi1121.png eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumi1104.png eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumi1058.png eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumi1005.png eps file
ATLAS instantaneous luminosity
ATLAS instantaneous luminosity profiles as measured online during four consecutive LHC fills with 7 TeV centre-of-mass energy and stable beams between July 12 and 15, 2010. The gray shaded curves give the delivered luminosity, the green shaded curves show the delivered luminosity during stable beam conditions allowing ATLAS to turn on their tracking devices, and the yellow shaded curves give the recorded luminosity with the entire detector available.

The total time of stable beams during these fills is 41.8 hours. The total delivered (recorded) luminosity is 142.5 nb−1 (138.9 nb−1). The luminosity values given have been calibrated with van-der-Meer beam-separation scan data. The error on the luminosity is estimated to be 11%, dominated by the uncertainty in the beam intensities.

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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/lumiJuly12-15.png
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Specific Luminosity per BCID
Distribution of the specific luminosity recorded by ATLAS at 7 TeV for different LHC bunches (BCID), averaged over LHC fill 1256. The specific luminosity is defined as the luminosity per bunch and per unit bunch charge, and is inversely proportional to the product of the horizontal and vertical convolved beam sizes at the IP. Due to the fill pattern, of the 25 bunches in each ring, only 16 are colliding in IP1; the background from the bunches that do not collide in ATLAS remains invisible on a linear scale, since it lies almost four orders of magnitude below the actual luminosity. The maximum bunch-to-bunch spread in specific luminosity approaches 40%, implying a variation of almost a factor of 2 in the product of the horizontal and vertical emittances of colliding-bunch pairs.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/fill1256_bcidspec.png
Luminosity per BCID
Time evolution of the bunch-by-bunch instantaneous luminosity recorded by ATLAS at 7 TeV during LHC fill 1257. In this fill there were 16 bunch pairs colliding at the ATLAS interaction point IP1. The difference, at a given time, between the highest- and the lowest-luminosity bunch is a factor of about 1.6, reflecting the variation of bunch currents and emittances along the colliding-bunch trains.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/OperationalPlots/fill1257_bcthlum.png

Comparisons of Different Methods Measuring the Luminosity

ATLAS instantaneous luminosity comparing LAr, MBTS and LUCID
The ATLAS instantaneous luminosity as determined with the LAr (blue open circles), the LUCID (open squares), and MBTS (red triangles) sub-detectors (ATLAS run 152409). The two plots give the instantaneous luminosity with two different y-scale ranges. The LAr instantaneous luminosity is corrected for the dead time in the data acquisition system, and therefore is an estimate of the LHC delivered luminosity at the ATLAS interaction point. Both the MBTS and the LUCID methods are not affected by data acquisition dead time. For each of these measurements the acceptance is independently calculated using the PYTHIA Monte Carlo simulation of the proton-proton inelastic interactions. The corresponding cross section used to normalize the measurements is 71.5 mb and it includes non-diffractive, single-diffractive, and double-diffractive processes. The systematic uncertainty is dominated by model dependence in the diffractive components of the cross section. An indication of the size of this uncertainty is obtained by comparing PYHTIA and PHOJET which translates into a variation in the luminosity of about 15%. The uncertainty is 100% correlated between methods. The uncorrelated method-dependent systematic uncertainties are of order 5% for LAr, LUCID, and MBTS. The curves show only the statistical error as the systematic uncertainty is time independent. The statistical errors on the plots are not clearly visible as they are small compared to the size of the markers. For this run the estimated delivered luminosity is (75.6 ± 15.1) μ b−1(stat+syst).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/MBTS_LUCID_LAr/run152409_absolute_luminosity_0.png
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Measurement of Rate of Events with at least one Track and corresponding Luminosity for fill 1005

First Plot: Rate of events in LHC Fill 1005 with at least one charged primary particle with pT>0.5 GeV/c, |eta|<0.8, versus UTC time (solid markers). Also shown is the raw rate of events with at least one track in this acceptance range (dashed line). The correction factor applied to the raw rate to obtain the charged particle rate is 1.04 +\- 0.017. Error bars represent the statistical uncertainty, the colored bands include both the systematic and statistical uncertainties.

Second Plot: The instantaneous luminosity derived from counting of events with at least one charged primary particle (pT>0.5 GeV/c, |eta|<0.8) for LHC Fill 1005 as a function of UTC time. Pythia MC09 was used for the acceptance and cross-section models after the correction for tracking, vertex and trigger efficiencies. Error bars represent the statistical uncertainty, the colored bands include both the systematic and statistical uncertainties. The systematic uncertainties account for the correction procedure and the dependence on the Monte Carlo models used for the acceptance and cross-sections by comparing the results obtained with Pythia MC09 and Phojet.

Third Plot: The instantaneous luminosity derived from counting of events with at least one charged primary particle (pT>0.5 GeV/c, |eta|<0.8) for LHC Fill 1005 as a function of UTC time (black points) compared with the Van der Meer calibrated ATLAS luminosity measurement (blue triangles). Pythia MC09 was used for the acceptance and cross-section models for the charged particle analysis. Error bars represent the statistical uncertainty, the colored bands include both the systematic and statistical uncertainties. The systematic uncertainties on the charged particle method account for the correction procedure and the dependence on the Monte Carlo models used for the acceptance and cross-sections by comparing the results obtained with Pythia MC09 and Phojet.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/Track/TrackRate.152166.png
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/Track/TrackLumi.152166.png
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/Track/TrackLumivsLarLumi.152166_wVdM.png
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Measurement of Rate of Events with at least one Track and corresponding Luminosity for fill 1089

First Plot: Rate of events in LHC Fill 1089 with at least one charged primary particle (pT > 0.5 GeV, |η| < 0.8) versus UTC time for recorded events (black open circles), and corrected for pile-up (red filled circles). The pile-up correction (μ-correction) was performed as detailed in Equation 2 of ATLAS-CONF-2010-060. The error bars include the statistical uncertainty and the 1.7% uncertainty on the track to particle correction factor of 1.04. This fill corresponds to four ATLAS runs, therefore periods in between runs are empty, as well as the period of the van der Meer scan and periods when the Inner Detector was not fully operational.

Second Plot: The cross section measured in LHC Fill 1089 for events with at least one charged primary particle (pT > 0.5 GeV, |η| < 0.8) versus UTC time. The error bars include the statistical uncertainty and the 1.7% uncertainty on the track to particle correction factor of 1.04. The average cross-section is 42.3 ± 0.7 (stat. + sys.) mb. The scale uncertainty of 11% in the luminosity used to calculate the cross section from the event rate is not included. This fill corresponds to four ATLAS runs, therefore periods in between runs are empty, as well as the period of the van der Meer scan and periods when the Inner Detector was not fully operational.

For details on the event selection see also ATLAS-CONF-2010-101.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/Track/fill1089TrkRate.png
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/Track/fill1089_sigChPart.png
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Detailed plots on the van der Meer scan from October 2010

For a detailed explanation of all the terms please refer to Luminosity Determination in pp Collisions at sqrt(s)=7 TeV Using the ATLAS Detector at the LHC


The following pages show the results of performing a χ2 fit of a double Gaussian plus constant term to the data. A total of 48 fits are performed corresponding to 2 algorithms*2 scans*2 planes*6 BCIDs. The ordinate is the average visible number of inelastic interactions per bunch crossing (BC), μvis, divided by the product of beam intensities at that point, n1n2, which removes sensitivity of the distributions to decaying beam intensities. The black points show this parameter calculated from LUCID raw data as a function of nominal separation in the plane under consideration. Statistical errors bars are shown but are typically smaller than the marker size. The blue dashed line shows the result of the fit to the data points. For LUCID_Event_OR fits are replotted on a log scale to demonstrate that the measured tails are well modelled by the chosen parameterisation. Here only a selection of fit results are shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/ORFitResults/x4.png
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/ORFitResults/x4log.png
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/ANDFitResults/x4.png
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The fitted nominal separation at the peak of the double Gaussian, x0, is compared by BCID between each algorithm and scan for the horizontal plane.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/Fittedx0.png
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The fitted nominal separation at the peak of the double Gaussian, y0, is compared by BCID between each algorithm and scan for the vertical plane.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/Fittedy0.png
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The measured convoluted horizontal beam size, Σx, is compared by BCID between algorithms and scans.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/FittedCapSigmaX.png
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The measured convoluted horizontal beam size, Σy, is compared by BCID between algorithms and scans.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/FittedCapSigmaY.png
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For all 48 fits to data the calculated χ2/DoF values are plotted to demonstrate the fit quality.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/Chi2perDoF.png
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The fitted peak values of μVIS/(n1n2) at x0 and y0 for the LUCID_Event_OR algorithm are compared by BCID for each scan.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/FittedORPeak.png
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The fitted peak values of μVIS/(n1n2) at x0 and y0 for the LUCID_Event_AND algorithm are compared by BCID for each scan.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/FittedANDPeak.png
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Summary plots of the measured visible cross-sections, σVIS, are shown comparing the results for each scan. There is one comparison plot for LUCID_Event_OR and one for LUCID_Event_AND. In each plot the weighted mean of scan IV (V) is shown as a dotted (dash-dotted) vertical line. The yellow band corresponds to a 0.5% window around the weighted mean of all 12 calculated cross-section values.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/sigma_visOR.png
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https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/sigma_visAND.png
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Horizontal and vertical convolved beam sizes obtained from double gaussian fits to bunch-by-bunch van der Meer scan data of the BCM-Event-OR algorithm in LHC fill 1386. Results of the two scans are shown separately indicating a clear broadening due to emittance growth in the vertical plane only. The time between two scans over the same coordinate was 30 minutes. Error bars reflect fit statistics only.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/BCM/SigmaXvsBCID_BCM.png
eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/BCM/SigmaYvsBCID_BCM.png
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The measured convoluted horizontal beam size, Σy, is compared by BCID between algorithms and scans between LUCID and BCM for all bunch crossings.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/CapSigma_BCM_vs_LUCID_x.png
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The measured convoluted vertical beam size, Σy, is compared by BCID between algorithms and scans between LUCID and BCM for all bunch crossings.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/VdmLucid_Oct2010/SummaryPlots/CapSigma_BCM_vs_LUCID_y.png
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Satellite Bunches in Heavy Ion running


The red histogram shows the difference between the arrival time of hits in the Minimum Bias Trigger Scintillators (MBTS) on the two sides of ATLAS, requiring that at least 14 of the 16 counters be hit. This is shown for LHC fill 1533 during the 2010 Heavy-Ion run. The main peak corresponds to in-time collisions; the small peaks are interpreted as collisions of a main bunch from one beam with satellite bunches from the other beam. At the edges (|ΔT|>18ns) there is a large contamination from beam-halo events which masks any satellite collisions. Particles produced upstream of the detector which travel parallel to the beamline from one side of the MBTS to the other side have a transit time of about 21ns since the distance between the two MBTS detectors is 7.2m. The black histogram shows a measurement made by the LHC Longitudinal Density Monitor (LDM), with an integration time of 15 minutes during the same fill. Only the beam-2 LDM was available at this time and so the black histogram shows the convolution of the beam-2 longitudinal profile with the same profile reversed in time, as a proxy for the beam-1 profile. The longitudinal distribution of collisions in the detector mirrors the convolution of the longitudinal profiles of the two beams.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2010/Luminosity/SatelliteBunches-HI2010/satellites_fill1533.png
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BCM luminosity plots from 2011 running


Instantaneous luminosity of a single bunch (bunch slot 45) during LHC fill 2085 (ATLAS run 188921), as measured by the vertical BCM modules (BCM-V). The OR algorithm requires at least one hit in any of the four vertical BCM modules within the second half (12.5 ns) of the bunch-crossing interval. The XOR (exclusive-OR) algorithms require at least one hit in only one BCM arm (A-side or C-side), with no hit in the opposite arm (C or A, respectively). The AND algorithm requires a coincidence between the A and C arms of the detector; being the most selective one, it exhibits the largest statistical fluctuations. These four luminosity algorithms yield consistent results.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_bunch45.png
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Instantaneous luminosity measurement based on the OR algorithm, color-coded for individual colliding bunches. Data from BCM vertical modules (BCM-V) are shown over LHC fill 2085 (ATLAS run 188921) for all 423 colliding bunches. For an event to satisfy the OR condition, it must contain at least one hit in any of the four vertical BCM modules within the second half (12.5 ns) of the bunch-crossing interval.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_bunches_OR.png
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Total instantaneous luminosity delivered to ATLAS in LHC fill 2085 (ATLAS run 188921), as measured by the vertical BCM modules (BCM-V) and summed over all 423 bunches colliding in ATLAS. The OR algorithm requires at least one hit in any of the four vertical BCM modules within the second half (12.5 ns) of the bunch-crossing interval. The XOR (exclusive-OR) algorithms require at least one hit in only one BCM arm (A-side or C-side), with no hit in the opposite arm (C or A, respectively). The AND algorithm requires a coincidence between the A and C arms of the detector. These four luminosity algorithms yield consistent results.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_total.png
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Distribution of integrated luminosity recorded at different average number of proton-proton (pp) interactions per bunch crossing, assuming an inelastic pp cross-section of 60.3 mb. The data represents ATLAS run 188921 and is based on the OR algorithm, processing signals from BCM vertical modules (BCM-V).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_integrated_run_OR.png
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Integrated luminosity for LHC fill 2085 (ATLAS run 188921), based on the OR algorithm applied to the vertical BCM modules (BCM-V). The horizontal axis denotes the sequential number of possible bunch slots, and extends over all 3564 slots covering the entire LHC beam. The bunch-train structure of the beam is clearly visible, as well as the relative magnitude of the luminosity and beam-background signals in, respectively, the colliding bunches and the unpaired bunches (bunch slots 1770-1850 and 2660-2740). Each bunch-train is followed by the afterglow.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_map_OR.png
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Integrated luminosity for LHC fill 2085 (ATLAS run 188921), based on the XOR-A algorithm applied to the vertical BCM modules (BCM-V). The horizontal axis denotes the sequential number of possible bunch slots, and extends over all 3564 slots covering the entire LHC beam. The bunch-train structure of the beam is clearly visible, as well as the relative magnitude of the luminosity and beam-background signals in, respectively, the colliding bunches and the unpaired bunches (bunch slots 1770-1850). Each bunch-train is followed by the afterglow. In contrast to the results based on the OR algorithm, only one unpaired bunch train is visible. This demonstrates the background-selectivity of the XOR algorithm.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_map_XORA.png
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Integrated luminosity for LHC fill 2085 (ATLAS run 188921), based on the XOR-C algorithm applied to the vertical BCM modules (BCM-V). The horizontal axis denotes the sequential number of possible bunch slots, and extends over all 3564 slots covering the entire LHC beam. The bunch-train structure of the beam is clearly visible, as well as the relative magnitude of the luminosity and beam-background signals in, respectively, the colliding bunches and the unpaired bunches (bunch slots 2660-2740). Each bunch-train is followed by the afterglow. In contrast to the results based on the OR algorithm, only one unpaired bunch train is visible. This demonstrates the background-selectivity of the XOR algorithm.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_map_XORC.png
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Integrated luminosity for LHC fill 2085 (ATLAS run 188921), based on the AND algorithm applied to the vertical BCM modules (BCM-V). The horizontal axis denotes the sequential number of possible bunch slots, and extends over all 3564 slots covering the entire LHC beam. The bunch-train structure of the beam is clearly visible, as well as the relative magnitude of the luminosity and beam-background signals in, respectively, the colliding bunches and the unpaired bunches (bunch slots 1770-1850 and 2660-2740). The AND algorithm imposes a stricter selection, resulting in a strongly suppressed afterglow signal in the empty bunch slots (compared to the corresponding afterglow level when using the OR algorithms). In the nominally filled bunch slots however, the afterglow background to the BCM-AND algorithm arises from random coincidences between a genuine luminosity signal (XOR) in one BCM arm, and a random afterglow hit in the opposite arm; the afterglow correction to the absolute luminosity determined using the BCM-AND algorithms is therefore of comparable relative magnitude to that in the BCM-OR case.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/Luminosity/BCM_Dec_2011/bcm_lumi_map_AND.png
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Luminosity plots from 2011 running for lumi-days workshop (28 Feb 2012)


Intensity-normalised visible interaction rate vs. transverse beam separation measured using the LUCID_EvtOR luminosity algorithm during the 7TeV proton-proton May 2011 van der Meer scan, LHC fill 1783, for BCID 81. Shown are the horizontal (left) and vertical (right) scans. Upper panels: measured specific interaction rate, proportional to specific luminosity, and fitted function of Gaussian on a constant pedestal for the first (second) scan shown by the filled points and blue curve (open points and red curve) respectively. Bottom panels: Pulls of the fitted functions relative to the measured data for each scan.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCID81_final.png
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Intensity-normalised visible interaction rate vs. transverse beam separation measured using the LUCID_EvtOR luminosity algorithm during the 7TeV proton-proton May 2011 van der Meer scan, LHC fill 1783, for BCID 867. Shown are the horizontal (left) and vertical (right) scans. Upper panels: measured specific interaction rate, proportional to specific luminosity, and fitted function of Gaussian on a constant pedestal for the first (second) scan shown by the filled points and blue curve (open points and red curve) respectively. Bottom panels: Pulls of the fitted functions relative to the measured data for each scan.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCID867_final.png
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Intensity-normalised visible interaction rate vs. transverse beam separation measured using the LUCID_EvtOR luminosity algorithm during the 7TeV proton-proton May 2011 van der Meer scan, LHC fill 1783, for BCID 2752. Shown are the horizontal (left) and vertical (right) scans. Upper panels: measured specific interaction rate, proportional to specific luminosity, and fitted function of Gaussian on a constant pedestal for the first (second) scan shown by the filled points and blue curve (open points and red curve) respectively. Bottom panels: Pulls of the fitted functions relative to the measured data for each scan.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCID2752_final.png
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Fitted specific visible interaction rate at the peak of the 7TeV proton-proton van der Meer scans recorded in May 2011, for each of the 14 bunch pairs colliding in ATLAS. The luminosity was measured using the LUCID_EvtOR algorithm. The beam-separation scans were carried out in the following order: VII horizontal, VII vertical, VIII horizontal, VIII vertical. Emittance growth between scans leads to a widening of the beam profiles, and therefore a continuous decrease in specific luminosity. The scan curves are fitted to the sum of a Gaussian with constant background. While some bunch pairs (e.g. BCID 81) exhibit the expected decrease with time of the fitted peak interaction rate, in most BCID's the expected chronological hierarchy of the fitted peak rates is violated.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/peakGp0fit_final.png
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Measured specific visible interaction rate at zero nominal beam-separation during the 7TeV proton-proton van der Meer scans recorded in May 2011, for each of the 14 bunch pairs colliding in ATLAS. The luminosity was measured using the LUCID_EvtOR algorithm. The beam-separation scans were carried out in the following order: VII horizontal, VII vertical, VIII horizontal, VIII vertical. Emittance growth between scans leads to a widening of the beam profiles, and therefore to a continuous decrease of the specific luminosity. All bunch pairs exhibit the expected decrease with time of the peak interaction rate (within the statistical accuracy of the data).
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/peakmeas_final.png
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Fitted nominal beam separation at peak luminosity during horizontal van der Meer scans performed with 7TeV proton-proton collisions in May 2011. The values are extracted from fits of a Gaussian on top of a flat background to the specific interaction rates measured by four different LUCID detector algorithms. The bunch-averaged relative horizontal position of the two beams drifted by approximately 2 microns between the first (filled markers) and the second (open markers) horizontal scan. For BCIDs 81-331 the bunches collide at IP1 and IP5 only; bunches 817-967 collide in IP1, IP5 and IP2; and bunches 2602-2752 collide in IP1, IP5 and IP8. The different relative horizontal beam positions in the three groups reflect the cumulative effect of beam-beam deflections at IP5 and/or IP2 and/or IP8, where during the horizontal ATLAS scans the two beams were separated by ~ $1.4 \sigma$ in the horizontal plane.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/xmean.png
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Fitted nominal beam separation at peak luminosity during vertical van der Meer scans performed with 7TeV proton-proton collisions in May 2011. The values are extracted from fits of a Gaussian on top of a flat background to the specific interaction rates measured by four different LUCID detector algorithms. The bunch-averaged relative vertical position of the two beams drifted by approximately 1.5 microns between the first (filled markers) and the second (open markers) vertical scan. For BCIDs 81-331 the bunches collide at IP1 and IP5 only; bunches 817-967 collide in IP1, IP5 and IP2; and bunches 2602-2752 collide in IP1, IP5 and IP8. The different relative vertical beam positions in the three groups reflect the cumulative effect of beam-beam deflections at IP5 and/or IP2 and/or IP8, where during the vertical ATLAS scans the two beams were separated by ~ $1.4 \sigma$ in the vertical plane.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/ymean.png
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Comparison of measured visible cross-sections for the LUCID_EvtOR algorithm by the van der Meer method, for the first scan pair (scan VII) performed with 7TeV proton-proton collisions in May 2011. The luminosity-scan curves are fitted using either a Gaussian (plus flat background) or the spline method. The difference in the bunch-averaged visible cross-sections is 0.2% between the two methods and this difference is less than the relative spread in cross-sections across BCIDs for the individual methods.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/LUCIDOR_SplinevsGaus_final.png
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Comparison of measured visible cross-sections for the LUCID_EvtOR algorithm by the van der Meer method, for the first scan pair (scan VII) performed with 7TeV proton-proton collisions in May 2011. The luminosity-scan curves are fitted by the spline method, either with (green squares) or without (red circles) prior subtraction of afterglow and beam-gas backgrounds. The difference between bunch-averaged visible cross-sections is less than 0.1%, indicating that the systematic uncertainty associated with background subtraction is negligible for this luminosity algorithm.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/LUCIDOR_SplineBkgd_final.png
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Intensity-normalized visible interaction rate vs. transverse beam separation, measured using the LUCID_EventOR luminosity algorithm during the 2.76TeV proton-proton March 2011 van der Meer scan (LHC fills 1563 & 1658), for BCID 517, for horizontal (left) and vertical (right) scans. Upper panel: measured specific interaction rate (proportional to the specific luminosity), shown by filled (first scan) and open (second scan) circles, and fitted (blue and red curves) to a Gaussian on top of a constant pedestal. Lower panel: pulls of the fits vs. beam separation; unlike the first scan, the vertical data from the second scan shows poor agreement with the choice of fit model indicating significant fill dependence of the scan profile in that plane.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/March_BCIDFit.png
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Relative variation in the measured visible cross-section from the average visible cross-section as a function of BCID. Data for the LUCID_EventOR and LUCID_EventAND algorithms are shown for the 2.76TeV proton-proton March 2011 van der Meer scan in LHC fill 1653. It can be seen that the spread of results is consistent between the algorithms and the the relative deviation from the average is no worse than +/-2%.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/March_sigmavis_rel.png
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Relative variation in the measured visible cross-section from the average visible cross-section as a function of the average LHC beam bunch current product (BCP) in a BCID. The average BCP is defined as the average of that measured at zero nominal separation in the horizontal scan and that measured at zero nominal separation in the vertical scan. Data for the LUCID_EventOR and LUCID_EventAND algorithms are shown for the 2.76TeV proton-proton March 2011 van der Meer scan in LHC fill 1653. A systematic decrease is observed with increasing BCP suggesting that the spread in measured results can be partly explained by an offset in the measured LHC beam Intensities.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/March_sigmavis_rel_BCP.png
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2011 Luminosity measurements long term stability


Fractional deviation in the value of mu (the mean number of inelastic pp collisions per bunch crossing) with respect to the BCM-H EventOR luminosity algorithm, obtained using different luminosity detectors and as a function of the mu value measured bunch-by-bunch by the BCM-H detector during the high-luminosity pile-up scan in September 2011 (LHC fill 2086). The high-mu values correspond to the beams being well centered on each other, while the lowest mu values correspond to the beams being almost totally separated in the transverse plane. The absolute luminosity calibrations of the BCM algorithms are those derived from the May 2011 van der Meer scans (LHC fill 1783). The LUCID tubes were operated under vacuum, with the absolute scale of the LUCID luminosity measurement cross-calibrated to that of the TILE measurements during a long, high-luminosity run (LHC fill 2105). The LUCID and BCM luminosity measurements are corrected for mu-dependent afterglow and beam-gas backgrounds. The divergences at very low mu are attributed to imperfect background subtractions that become fractionally larger as the absolute luminosity decreases.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/muScan_3_perBCID_Figure1.png
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Fractional deviation in the average value of ⟨mu⟩ (the mean number of inelastic pp collisions per bunch crossing) with respect to the BCM-H EventOR luminosity algorithm, obtained using different luminosity detectors and averaged over all colliding bunches, as a function of the ⟨mu⟩ value measured by the BCM-H detector during the high-luminosity pile-up scan in September 2011 (LHC fill 2086). The absolute luminosity calibrations of the BCM algorithms are those derived from the May 2011 van der Meer scans (LHC fill 1783). The absolute scale of the TILE luminosity measurements was pegged to that of the LUCID EventOR measurements during that same fill (during which the LUCID tubes were filled with gas). The absolute scale of the FCal measurements was extracted from a linear fit of the FCal response to that of BCM EventOR luminosity measurement during this same pile-up scan (LHC fill 2086). The LUCID tubes were operated under vacuum, with the absolute scale of the LUCID luminosity measurement cross-calibrated to that of the TILE measurements during a long, high-luminosity run (LHC fill 2105). The LUCID and BCM luminosity measurements are corrected for mu-dependent afterglow and beam-gas backgrounds. The divergences at very low μ are attributed to imperfect background (LUCID, BCM) or pedestal (FCal, TILE) subtractions that become fractionally larger as the absolute luminosity decreases.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/muScan_3_perLB_Figure2.png
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Fractional deviation in the average value of ⟨mu⟩ (the mean number of inelastic pp collisions per bunch crossing) with respect to the BCM-H EventOR luminosity algorithm, obtained using different luminosity detectors and as a function of time. Each point shows the deviation for a single ATLAS run, averaged over all colliding bunches and over the duration of that run. The statistical uncertainties per point are negligible. The absolute luminosity calibrations of the BCM algorithms are those derived from the May 2011 van der Meer scans (LHC fill 1783). The absolute scale of the TILE luminosity measurements was pegged to that of the LUCID EventOR measurements during that same fill (during which the LUCID tubes were filled with gas). Because the FCal sensitivity is insufficient for the very- low luminosity conditions of fill 1783, the absolute scale of the FCal gap-current measurements was pegged to that of BCM-H EventOR measurements during the high-luminosity pile-up scan (LHC fill 2086). The LUCID measurements presented here are restricted to those periods after 11 July 2011 during which the LUCID tubes were operated under vacuum, with the absolute scale of the LUCID luminosity measurement cross-calibrated to that of the TILE measurements during a long, high-luminosity run (LHC fill 2105).
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/time_consistency_physics_Figure3.png
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Fractional deviation in the average value of ⟨mu⟩ (the mean number of inelastic pp collisions per bunch crossing) with respect to the BCM-H EventOR luminosity algorithm, obtained using different luminosity detectors and averaged over all colliding bunches in each ATLAS run, as a function of the ⟨mu⟩ value measured by the BCM-H detector. Each point shows the deviation averaged over 50 runs in 2011. The absolute luminosity calibrations of the BCM algorithms are those derived from the May 2011 van der Meer scans (LHC fill 1783). The absolute scale of the TILE luminosity measurements was pegged to that of the LUCID EventOR measurements during that same fill (during which the LUCID tubes were filled with gas). The increase of the TILE/BCM ratio around ⟨mu⟩ ∼ 8 is not caused by a μ-dependent, instrumental non-linearity: it reflects a ∼ 0.5% step change in the relative TILE response between mid- August and early September 2011. Because the FCal sensitivity is insufficient for the very-low luminosity conditions of fill 1783, the absolute scale of the FCal gap-current measurements was pegged to that of BCM-H EventOR measurements during the high-luminosity pile-up scan (LHC fill 2086). The LUCID measurements presented here are restricted to those periods after 11 July 2011 during which the LUCID tubes were operated under vacuum, with the absolute scale of the LUCID luminosity measurement cross- calibrated to that of the TILE measurements during a long, high-luminosity run (LHC fill 2105)
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/mu_consistency_physics_Figure4.png
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The maximum mean number of interactions per beam crossing for each LHC fill (above) and the number of bunch pairs colliding in ATLAS (below) are shown for the 7 TeV physics data col- Month in 2010 Month in 2011 lected in 2010-2011. The mean number of interactions is derived from the total luminosity according to ⟨mu⟩ = L sigma(inel) / (nb fr) where nb is the number of colliding bunches, fr is the LHC revolution frequency, and sigma(inel) is the pp inelastic cross-section, assumed to be 71.5 mb. Only regular physics fills at 7 TeV are shown; special-purpose fills, including van der Meer scans, are not included.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/Luminosity_Performance_Figure5.pdf
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2011 lenght scale calibration for pp luminosity calibration


Upper panel: vertical position, at optimal beam-beam overlap, of the luminous centroid mea- sured by the ATLAS Inner Detector vs. nominal amplitude of the vertical closed-orbit bump of beam 2. The statistical errors are smaller than the symbols. A linear fit to the data provides the absolute calibra- tion of the closed-orbit bump. The residual of this linear fit, shown in the lower panel, reveals a small (< 0.4 mm) non-linearity in the response of the beam position to the closed-orbit bump.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/LengthScaleCalibration_Figure6.pdf
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Plots from 2010 PbPb Van der Mer scan


Convolved horizontal and vertical beam-size ratios (Sigma_X and Sigma_Y) between ZDC sides A and C obtained per colliding bunch (labeled by an integer BCID) during the PbPb November 2010 van der Meer scans. The analysis relies on events triggered by the ZDC_A (inclusive OR on the A side), ZDC_C (inclusive OR on the C side). In order to obtain the visible interaction rate for the visible cross section determination, single gaussian function fits were performed and the corresponding convolved beam sizes (Sigma_X, Sigma_Y) were extracted for each scan. The two top plots show respectively, the horizontal plane Sigma_X$ and the vertical plane Sigma_Y ratios between ZDC_A and ZDC_C for the first set of scans, and the two bottom plots the same ratios for the second set. A statistically significant discrepancy at the level of 0.2-0.6\% is observed between the convolved widths measured on the A and C sides.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/PbPb_2010_CapSigmaRatiov4.png
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Preliminary plots from April 2012 VdM luminosity calibration at 8 TeV and 2012 luminosity stability


Sigma_x determined by BCMV EventOR algorithms per BCID for scans I, II and III. The error bars represent statistical uncertainties only.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCMV_EventOR_capSigX.png
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Sigma_y determined by BCMV EventOR algorithms per BCID for scans I, II and III. The error bars represent statistical uncertainties only.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCMV_EventOR_capSigY.png
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Comparison of the specific luminosity determined by BCMV and LUCID per BCID for scans I, II and III. This figure shows the specific luminosity values determined by BCMV EventOR. The error bars represent statistical uncertainties only.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCMV_EventOR_Lspec.png
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Comparison of the specific luminosity determined by BCMV and LUCID per BCID for scans I, II and III. This figure shows the ratio of the specific luminosity determined by BCMV EventOR and LUCID EventOR. The vertical lines indicate the weighted average of this ratio over BCIDs for scans I, II and III separately. The error bars represent statistical uncertainties only.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/LUCID_EventOR_bcmLucidRatio.png
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The specific visible interaction rate per bunch crossing mu visible(MAX) / (n1 n2), observed at the peak of each scan curve determined by BCMV EventOR per BCID for scans I, II and III. The error bars represent statistical uncertainties only.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCMV_EventOR_PeakMu.png
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Measured sigma(visible) values for BCMV EventOR by BCID for scans I, II and III. The error bars represent statistical uncertainties only. The vertical lines indicate the weighted average over BCIDs for scans I, II and III separately. The yellow band indicates a +- 2.1 % variation from the average, which is the systematic uncertainty evaluated from the per-BCID and per-scan sigma(visible) consistency.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/BCMV_EventOR_SigmaVis.png
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Measured sigma(visible) values for LUCID EventOR by BCID for scans I, II and III. The error bars represent statistical uncertainties only. The vertical lines indicate the weighted average over BCIDs for scans I, II and III separately. The yellow band indicates a +- 2.1 % variation from the average, which is the systematic uncertainty evaluated from the per-BCID and per-scan sigma(visible) consistency.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/LUCID_EventOR_SigmaVis.png
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Fractional deviation in the number of interactions per bunch crossing mu (averaged over BCIDs), obtained using different algorithms with respect to the BCMV EventOR value as a function of time in 2012. Each point shows the mean deviation for a single run compared to a reference run taken on May 21, 2012. Cesium-based corrections have been applied to the TILE readings to account for photomultiplier gain drift. Statistical uncertainties are shown per point, but in most cases are negligible.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/time_v6_Tile-CesiumCorr.png
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Fractional deviation in the number of interactions per bunch crossing mu (averaged over BCIDs), obtained using different algorithms with respect to the BCMV EventOR value as a function of mu. The absolute luminosity scale of all luminosity algorithms was pegged to that of the BCMV EventOR algorithm using a single reference run taken on May 21, 2012. For the LUCID EventAND algorithm, the data above mu ~ 30 is omitted because of saturation. Cesium-based corrections have been applied to the TILE readings to account for photomultiplier gain drift. Statistical uncertainties are shown per point, but in most cases are negligible.
https://twiki.cern.ch/twiki/pub/AtlasPublic/LuminosityPublicResults/mu_v6_Tile-CesiumCorr.png
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Preliminary plots on luminosity distribution evolution during 2012 VdM scans


Evolution of the horizontal (a) and vertical (b) luminous-centroid (or `beamspot') positions during a horizontal beam-separation scan. At each step of the scan, the measured luminous-centroid position is extracted from an unbinned maximum likelihood fit of the observed spatial distribution of reconstructed vertices, using as a fit model a 3D single Gaussian corrected for the vertex position resolution. The uncertainties shown are statistical only. The simulated 3-D luminosity distribution, and the resulting evolution of the simulated luminous-centroid position, are computed numerically, at each step of the scan, from the time-overlap integral of the simulated density distributions of protons in a colliding-bunch pair.

(a) The horizontal luminous centroid during a horizontal vdM scan moves in the same direction as the beam with the narrower horizontal width. If the beam profiles (and therefore the luminosity distribution) are Gaussian then one would see only linear motion of the luminous centroid. The deviation from linearity requires the single beam profiles to be modelled as something more complicated. The density distribution of each bunch is modelled by the non-factorisable sum of three 3-D gaussians, the parameters of which are tuned to reproduce the evolution of the luminous centroid observed in the data. This model provides a satisfactory description of the data except at the largest beam separation. (b) The vertical luminous centroid position during a horizontal vdM scan would be constant if there were no transverse correlation in the single beam profiles (and therefore neither in the luminosity distribution). The density distribution of each bunch is modelled by the non-factorisable sum of three 3-D gaussians, the parameters of which are tuned to reproduce the evolution of the luminous centroid observed in the data. This model provides a satisfactory description of the data. Note that a simulation in which the individual beam profiles are modelled by 3-D single gaussians could also describe these data if one or both of the beams had some degree of transverse correlation.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/jul12_xposition_centred_xscan.png
eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/nov12_yposition_centred_xscan.png
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Evolution of the horizontal (a) and vertical (b) luminous (or `beamspot') widths during a horizontal beam-separation scan. At each step of the scan, the measured luminous width is extracted from an unbinned maximum likelihood fit of the observed spatial distribution of reconstructed vertices, using as a fit model a 3D single Gaussian corrected for the vertex position resolution. The uncertainties shown are statistical only. The simulated 3-D luminosity distribution, and the resulting evolution of the simulated luminous width, are computed numerically, at each step of the scan, from the time-overlap integral of the simulated density distributions of protons in a colliding-bunch pair. The RMS of the luminosity distribution is used as an estimator of this width.

(a) The horizontal luminous widthd uring a horizontal vdM scan wouldn ot vary if each individual beam profile were modelled by a 3-D single Gaussian. The increase in luminous width with separation (and then decrease again at large separations) requires a more complicated model. The density distribution of each bunch is modelled by the non-factorisable sum of three 3-D gaussians, the parameters of which are tuned to reproduce the evolution of the luminous centroid observed in the data. This model is able to provide the qualitative features needed for describing the observed variation in width.

(b) The vertical luminous width during a horizontal vdM scan will vary if there is some non-linear transverse correlation in at least one of the beams. The variation in width points to non-factorisation effects in the transverse beam distribution. The density distribution of each bunch is modelled by the non-factorisable sum of three 3-D gaussians, the parameters of which are tuned to reproduce the evolution of the luminous centroid observed in the data. This model provides a satisfactory description of the data.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/jul12_xwidth_centred_xscan.png
eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/jul12_ywidth_centred_xscan.png
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Evolution of the horizontal (a) and vertical (b) luminous (or `beamspot') widths during a horizontal beam-separation scan. At each step of the scan, the measured luminous width is extracted from an unbinned maximum likelihood fit of the observed spatial distribution of reconstructed vertices, using as a fit model a 3D single Gaussian corrected for the vertex position resolution. The uncertainties shown are statistical only. The simulated 3-D luminosity distribution, and the resulting evolution of the simulated luminous width, are computed numerically, at each step of the scan, from the time-overlap integral of the simulated density distributions of protons in a colliding-bunch pair. The RMS of the luminosity distribution is used as an estimator of this width.

(a) The horizontal luminous width during a horizontal vdM scan would not vary if each individual beam profile were modelled by a 3-D single Gaussian. The increase in luminous width with separation (and then decrease again at large separations) requires a more complicated model. However unlike the data from the July vdM scan session (Figure 2), in November the luminosity distribution width initially decreases as a function of separation before increasing again at large separation. The double (or triple) Gaussian model is insufficient to describe these observations.

The three grey curves show the results of three simulations in which the density distribution of each bunch is modelled by 3-D double gaussians in each case with slightly varying parameter choices, but in each the two beams are identical. A double Gaussian (gDG) is the non-factorisable sum of two normalised 3-D single Gaussians (gA and gB) in which gA is weighted by a parameter, f , the fraction and gB by 1 - f . The first grey curve (a straight horizontal line) is the case when the horizontal widths of Gaussians A and B are equal. The second, in which the horizontal luminous width continues increasing with separation, is the case when the horizontal width of Gaussian A is greater than that of B. The third grey line, in which the horizontal luminous width increases initially with separation and then starts decreasing is the case in which the width of Gaussian B is greater than that of A. Note that for each curve the vertical width of Gaussian B is greater than the vertical width of Gaussian A.

A model for the density distribution of each bunch which does describe the data satisfactorily is the non-factorisable sum of two 3-D supergaussians (double supergaussian), the parameters of which are tuned to reproduce the evolution of the luminous centroid observed in the data. In one dimension a supergaussian is an extension of a single Gaussian and has the form gSG(x) = A.exp(-0.5*(|x-mu|/sigma)**(2+epsilon)) where A is a normalisation constant, mu is the mean, sigma is the width and epsilon is a small number. In the case epsilon=0, the sthe single Gaussian distribution is recovered. The supergaussian provides an acceptable parameterisation of the data except at the largest beam separation.

(b) Any variation of vertical luminous width during a horizontal scan is indicative of non-factorisation of the luminosity distribution. Figure 2(b) showed data from the July 2012 scan session and showed significant variation in luminous width with separation. Figure 3(b) shows data from November and it is observed that the variation is much less. This suggests that the vdM formalism used to calibrate the luminosity is likely to hold better in November than in July.

The data is compared to a simulation in which the density distribution of each bunch is modelled by the non-factorisable sum of two 3-D supergaussians, the parameters of which are tuned to reproduce the evolution of the luminous centroid observed in the data. The model provides an acceptable parameterisation of data except at the largest beam separation. In this case (unlike for (a)) a simulation using double Gaussian beam profiles would have also been able to describe the data.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/nov12_xwidth_centred_xscan.png
eps file https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/nov12_ywidth_centred_xscan.png
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Preliminary plots on evolution of convolved beam width during 2012 VdM scans


Time evolution of the horizontal convolved beam size Sigmax for five different colliding-bunch pairs (BCID's), measured using the LUCID EventOR luminosity algorithm during the van der Meer scan session of July 19, 2012. The beams remained vertically centred on each other during the first three scans (the first scan) of LHC fill 2855 (fill 2856), and were separated vertically by 344 microns during the last scan in each fill. In both fills, the horizontal convolved beam size is significantly larger when the beams are vertically separated, demonstrating that the horizontal luminosity distribution depends on the vertical beam separation, i.e., that the horizontal & vertical luminosity distributions do not factorise.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/S4_S5_S6_S7_S8_S9_timePlot_lucidEvtOR_CSx_orbCorr.png
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Time evolution of the horizontal convolved beam size Sigmax for five different colliding-bunch pairs (BCID's), measured using the LUCID EventOR luminosity algorithm during the van der Meer scan session of November 22, 2012. The beams remained vertically centred on each other during the first, second and last scans. They were separated vertically by 344 (197) microns during the third (fourth) scan. The horizontal convolved beam size increases with time at an approximately constant rate, reflecting transverse-emittance growth. No significant change in Sigmax is observed when the beams are separated vertically, suggesting that the horizontal luminosity distribution is roughly independent of the vertical beam separation, i.e., that the horizontal & vertical luminosity distributions approximately factorise.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/S10_S11_S12_S13_S14_timePlot_lucidEvtOR_CSx_orbCorr.png
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Preliminary plots on long term stability of the various luminosity detectors in 2012


Fractional deviation in the number of interactions per bunch crossing (averaged over all colliding bunch pairs), obtained using different algorithms with respect to the BCMV EventOR value as a function of time in 2012. Each point shows the mean deviation for a single run compared to a reference run taken on October 27, 2012. Statistical uncertainties are shown per point, but in most cases are negligible. The BCM and LUCID detectors appear internally consistent over the whole of 2012 at the < 1% level.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/longtermstab2012Stable.png
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Fractional deviation in the number of interactions per bunch crossing (averaged over all colliding bunch pairs), obtained using different algorithms with respect to the BCMV EventOR value as a function of time in 2012. Each point shows the mean deviation for a single run compared to a reference run taken on October 27, 2012. Cesium-based corrections have been applied to the TILE readings to account for photomultiplier gain drift. Statistical uncertainties are shown per point, but in most cases are negligible. The calorimeters and MPX (Medipix) detectors suggest a drift of 2% with respect to BCM.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/longtermstab2012Drift.png
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Fractional deviation in the number of interactions per bunch crossing (averaged over all colliding bunch pairs), obtained using different algorithms with respect to the BCMV EventOR value as a function of time in 2012. Each point shows the mean deviation for a single run compared to a reference run taken on October 27, 2012. Cesium-based corrections have been applied to the TILE readings to account for photomultiplier gain drift. Statistical uncertainties are shown per point, but in most cases are negligible.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/Luminosity/March2013/LumiPlots/pngPlots/longtermstab2012All.png
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Older plots with partial 2011 or 2012 data sets

Multiple years distribution of the mean number of interactions

Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2011 and 2012 data. This shows the full 2011 run and 2012 data taken between April 4th and Novemebr 26th The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing calculated for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 71.5 mb for 7TeV collisions and 73.0 mb for 8TeV collisions, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2011_2012-nov.png
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Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2011 and 2012 data. This shows the full 2011 run and 2012 data taken between April 4th and September 17th. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing calculated for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 71.5 mb for 7TeV collisions and 73.0 mb for 8TeV collisions, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2011_2012-september2012.png
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Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2011 and 2012 data. This shows the full 2011 run and 2012 data taken between April 4th and June 18th. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing calculated for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 71.5 mb for 7TeV collisions and 73.0 mb for 8TeV collisions, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2011_2012.png
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partial 2012 data distribution of the mean number of interactions per crossing

Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for 2012 taken upto November 26th. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 73 mb, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2012-nov.png
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Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for 2012 taken upto September 17th. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 73 mb, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2012-september2012.png
eps file
Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for 2012 taken upto June 18th. The integrated luminosities and the mean mu values are given in the figure. The mean number of interactions per crossing corresponds the mean of the poisson distribution on the number of interactions per crossing for each bunch. It is calculated from the instantaneous per bunch luminosity as μ=Lbunch x σinel / fr where Lbunch is the per bunch instantaneous luminosity, σinel is the inelastic cross section which we take to be 73 mb, nbunch is the number of colliding bunches and fr is the LHC revolution frequency. More details on this can be found in arXiv:1101.2185.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/InteractionsperCrossing/muplot/2012/mu_2012.png
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Old plots of integrated luminosity based on online normalization

These plots have been superseeded by the most recent ones using the latest offline luminosity normalization

2012 data

Luminosity versus day

Total Integrated Luminosity in 2012
Cumulative luminosity versus day delivered to (green), and recorded by ATLAS (yellow) during stable beams and for pp collisions at 8 TeV centre-of-mass energy in 2012. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to turn the sensitive detector off to allow a beam dump or beam studies. Given is the luminosity as determined from counting rates measured by the luminosity detectors. These detectors have been calibrated with the use of the van-der-Meer beam-separation method, where the two beams are scanned against each other in the horizontal and vertical planes to measure their overlap function.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/sumLumiByDay.png
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logarithmic y-scale version
logarithmic y-scale version eps file
Integrated Luminosity per day in 2012
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/lumiByDay.png
eps file
logarithmic y-scale version
logarithmic y-scale eps file
Peak Luminosity per day in 2012
The maximum instantaneous luminosity versus day delivered to ATLAS. The luminosity determination is the same as described above for the integrated luminosity. Only the peak luminosity during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/peakLumiByFill.png
eps file

Luminosity versus week

Total Integrated Luminosity
Cumulative luminosity versus week delivered to (green), and recorded by ATLAS (yellow) during stable beams and for 8 TeV centre-of-mass energy. The definition is identical to the daily luminosity plots above.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/sumLumiByWeek.png
eps file
logarithmic y-scale version
logarithmic y-scale version eps file
Integrated Luminosity per week
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2012/DataSummary/figs/lumiByWeek.png
eps file
logarithmic y-scale version
logarithmic y-scale eps file

2011 data

Luminosity versus day

Total Integrated Luminosity in 2011
Cumulative luminosity versus day delivered to (green), and recorded by ATLAS (yellow) during stable beams and for pp collisions at 7 TeV centre-of-mass energy in 2011. The delivered luminosity accounts for the luminosity delivered from the start of stable beams until the LHC requests ATLAS to turn the sensitive detector off to allow a beam dump or beam studies. Given is the luminosity as determined from counting rates measured by the luminosity detectors. These detectors have been calibrated with the use of the van-der-Meer beam-separation method, where the two beams are scanned against each other in the horizontal and vertical planes to measure their overlap function.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/sumLumiByDay.png
eps file
logarithmic y-scale version
logarithmic y-scale version eps file
Integrated Luminosity per day in 2011
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/lumiByDay.png
eps file
logarithmic y-scale version
logarithmic y-scale eps file
Peak Luminosity per day in 2011
The maximum instantaneous luminosity versus day delivered to ATLAS. The luminosity determination is the same as described above for the integrated luminosity. Only the peak luminosity during stable beam periods is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/peakLumiByFill.png
eps file

Luminosity versus week

Total Integrated Luminosity
Cumulative luminosity versus week delivered to (green), and recorded by ATLAS (yellow) during stable beams and for 7 TeV centre-of-mass energy. The definition is identical to the daily luminosity plots above.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/sumLumiByWeek.png
eps file
logarithmic y-scale version
logarithmic y-scale version eps file
Integrated Luminosity per week
Same as above but not cumulative.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2011/DataSummary/figs/lumiByWeek.png
eps file
logarithmic y-scale version
logarithmic y-scale eps file


Major updates:
-- BeateHeinemann - 21-Mar-2011

Responsible: Guillaume Unal and Luca Fiorini

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Topic revision: r47 - 2018-08-24 - JeroenSchouwenberg
 
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