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LuminosityPublicResultsRun2

Introduction

Here any results related to ATLAS luminosity measurements in Run-2 are given. For Run-1 results, please see Luminosity Results for Run-1 (2010-2012).

Publications and Conference Results

Luminosity:

Satellite Bunches:

Multiple Year Collision Plots

These plots are based on the online luminosity estimate.

Delivered Luminosity versus time for 2011-2017 (p-p data only)
Cumulative luminosity versus day delivered to ATLAS during stable beams and for high energy p-p collisions.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2017/DataSummary/figs/intlumivsyear.png
eps file

Luminosity summary plots for 2017 pp data taking

These plots show the estimated integrated luminosity with a preliminary calibration for the 2017 data.

Total Integrated Luminosity in 2017
Cumulative luminosity versus time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2017. The delivered luminosity accounts for luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow for 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. Shown is the luminosity as determined from counting rates measured by the luminosity detectors. The luminosity shown represents a preliminary 13 TeV luminosity calibration for the 2017 data based on van-der-Meer beam-separation scans in 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2017/DataSummary/figs/sumLumiByDay.png
pdf file
Integrated Luminosity by Day in 2017
Integrated luminosity per day time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2017. The data shown is identical to the data shown above, except not cumulative over the year.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2017/DataSummary/figs/lumiByDay.png
pdf file
Peak Luminosity per Fill in 2017
The peak instantaneous luminosity delivered to ATLAS during stable beams for pp collisions at 13 TeV centre-of-mass energy is shown for each LHC fill as a function of time in 2017. The luminosity is determined using counting rates measured by the luminosity detectors, and is based on a preliminary analysis of van-der-Meer beam-separation scans during 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2017/DataSummary/figs/peakLumiByFill.png
pdf file
Peak Interactions per Crossing in 2017
The maximum number of inelastic collisions per beam crossing (µ) during stable beams for pp collisions at 13 TeV centre-of-mass energy is shown for each fill in 2017. The preliminary luminosity measurement is used to determine the number of interactions per beam crossing as µ = Lbunch x σinel / fr where Lbunch is the per-bunch instantaneous luminosity, σinel is the inelastic cross-section at 13 TeV, which is taken to be 80 mb, and fr is the LHC revolution frequency of 11.245 kHz. The number of interactions shown is averaged over all colliding bunch pairs, and only the peak value per fill during stable beams is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2017/DataSummary/figs/peakMuByFill.png
pdf file

Luminosity summary plots for 2016 pp data taking

These plots show the estimated integrated luminosity with the preliminary calibration update from February 2017.

Total Integrated Luminosity in 2016
Cumulative luminosity versus time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2016. The delivered luminosity accounts for luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow for 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. Shown 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 13 TeV luminosity calibration based on van-der-Meer beam-separation scans in 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/sumLumiByDay.png
pdf file
Integrated Luminosity by Day in 2016
Integrated luminosity per day time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2016. The data shown is identical to the data shown above, except not cumulative over the year.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/lumiByDay.png
pdf file
Peak Luminosity per Fill in 2016
The peak instantaneous luminosity delivered to ATLAS during stable beams for pp collisions at 13 TeV centre-of-mass energy is shown for each LHC fill as a function of time in 2016. The luminosity is determined using counting rates measured by the luminosity detectors, and is based on a preliminary analysis of van-der-Meer beam-separation scans during 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/peakLumiByFill.png
pdf file
Peak Interactions per Crossing in 2016
The maximum number of inelastic collisions per beam crossing (µ) during stable beams for pp collisions at 13 TeV centre-of-mass energy is shown for each fill in 2016. The preliminary luminosity measurement is used to determine the number of interactions per beam crossing as µ = Lbunch x σinel / fr where Lbunch is the per-bunch instantaneous luminosity, σinel is the inelastic cross-section at 13 TeV, which is taken to be 80 mb, and fr is the LHC revolution frequency of 11.245 kHz. The number of interactions shown is averaged over all colliding bunch pairs, and only the peak value per fill during stable beams is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/peakMuByFill.png
pdf file
Total Stable Beam Time by Day in 2016
Total Stable Beams Time - shown is the amount of time in stable beams delivered by the LHC each calendar day integrated over 2016. Also shown is the stable beams time multiplied by the L1 livefraction to show the amount of stable beams time recorded by ATLAS.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/sumTimeByDayUrgent.png
pdf file
Stable Beam Time in 2016
Stable Beams Time per day - shown is the amount of time in stable beams delivered by the LHC for each calendar day. Also shown is the stable beams time multiplied by the L1 livefraction to show the amount of stable beams time recorded by ATLAS.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/timeByDayUrgent.png
pdf file

Luminosity summary plots for 2016 pPb and Pbp data taking

Total Integrated Luminosity in 2016
Cumulative luminosity versus time delivered to (blue) and recorded by ATLAS (cyan) during stable beams for pPb and Pbp collisions at 5 TeV and 8 TeV centre-of-mass energy in 2016. The delivered luminosity accounts for luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow for 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. Shown is the luminosity as determined from counting rates measured by the luminosity detectors using a preliminary calibration.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016hi/DataSummary/figs/sumLumiByDayLogUrgent.png
pdf file
Integrated Luminosity by Day in 2016
Integrated luminosity per day time delivered to (blue) and recorded by ATLAS (cyan) during stable beams for pPb and Pbp collisions at 5 TeV and 8 TeV centre-of-mass energy in 2016. The data shown is identical to the data shown above, except not cumulative over the running period.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016hi/DataSummary/figs/lumiByDayLogUrgent.png
pdf file

Annual plots

They are based on the online luminosity determination

2016 pp Collisions

Pileup Interactions and Data Taking Efficiency

Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2016 pp collision data at 13 TeV centre-of-mass energy. All data delivered to ATLAS during stable beams is shown, and the integrated luminosity and the mean mu value are given in the figure. The mean number of interactions per crossing corresponds to the mean of the poisson distribution of 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 80 mb for 13 TeV collisions, and fr is the LHC revolution frequency. The luminosity shown represents the preliminary 13 TeV luminosity calibration released in February 2017, based on van-der-Meer beam-separation scans in 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2016.png
pdf file
eps file
Number of Interactions per Crossing
Same as above, but showing the combined 13 TeV data from 2015 and 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2015_2016_LHCC.png
pdf file
eps file
Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2016 pp collision data recorded from 16 April - 16 September at 13 TeV centre-of-mass energy. All data delivered to ATLAS during stable beams is shown, and the integrated luminosity and the mean mu value are given in the figure. The mean number of interactions per crossing corresponds to the mean of the poisson distribution of 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 80 mb for 13 TeV collisions, and fr is the LHC revolution frequency. The luminosity shown represents the preliminary 13 TeV luminosity calibration based on van-der-Meer beam-separation scans in 2016. This plot was first shown at the September 2016 LHCC meeting.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2016_LHCC.png
pdf file
eps file
Number of Interactions per Crossing
Same as above, but showing the combined 13 TeV data from 2015 and 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2015_2016_LHCC.png
pdf file
eps file
Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2016 pp collision data recorded from 16 April - 25 July at 13 TeV centre-of-mass energy. All data delivered to ATLAS during stable beams is shown, and the integrated luminosity and the mean mu value are given in the figure. The mean number of interactions per crossing corresponds to the mean of the poisson distribution of 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 80 mb for 13 TeV collisions, and fr is the LHC revolution frequency. The luminosity shown represents the preliminary 13 TeV luminosity calibration based on van-der-Meer beam-separation scans in 2016. This plot was first shown at ICHEP 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2016_ICHEP.png
pdf file
eps file
Number of Interactions per Crossing
Same as above, but showing the combined 13 TeV data from 2015 and 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2015_2016_ICHEP.png
pdf file
eps file
Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2016 pp collision data recorded from 16 April - 13 June at 13 TeV centre-of-mass energy. All data delivered to ATLAS during stable beams is shown, and the integrated luminosity and the mean mu value are given in the figure. The mean number of interactions per crossing corresponds to the mean of the poisson distribution of 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 80 mb for 13 TeV collisions, and fr is the LHC revolution frequency. The luminosity shown represents the initial 2016 13 TeV luminosity calibration which is based on the 2015 calibration. This plot was first shown at LHCP 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2016_LHCP.png
pdf file
eps file
Number of Interactions per Crossing
Same as above, but showing the combined 13 TeV data from 2015 and 2016.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/mu_2015_2016_LHCP.png
pdf file
eps file
Data Taking Efficiency per Day
ATLAS data taking efficiency in 2016. 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 one day. The empty bins are due to days in which no stable beams were delivered by the LHC. The inefficiency accounts for the time needed to turn on the high-voltage of the Pixel, SCT, and some of the muon detectors at the start of an LHC fill and any inefficiencies due to deadtime or due to individual problems with a given sub detector that prevents the ATLAS data taking to proceed.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/recEffByDay.png
pdf file
Data Taking Efficiency per Week
Same as above but per week.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/DataSummary/figs/recEffByWeek.png
pdf file

2015 pp Collisions

Pileup Interactions and Data Taking Efficiency

Number of Interactions per Crossing
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2015 pp collision data recorded from 3 June - 3 November at 13 TeV centre-of-mass energy. All data delivered to ATLAS during stable beams is shown, and the integrated luminosity and the mean mu value are given in the figure. The mean number of interactions per crossing corresponds to the mean of the poisson distribution of 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 80 mb for 13 TeV collisions, and fr is the LHC revolution frequency. The luminosity shown represents the preliminary 13 TeV luminosity calibration which was updated in December 2015.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/mu_2015.png
pdf file
eps file
Number of Interactions per Crossing
Same as above, but with data delivered in fills with 50ns and 25ns bunch spacing shown separately.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/mu_2015_2550.png
pdf file
eps file
Data Taking Efficiency per Day
ATLAS data taking efficiency in 2015. 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 one day. The empty bins are due to days in which no stable beams were delivered by the LHC. The inefficiency accounts for the time needed to turn on the high-voltage of the Pixel, SCT, and some of the muon detectors at the start of an LHC fill and any inefficiencies due to deadtime or due to individual problems with a given sub detector that prevents the ATLAS data taking to proceed.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/recEffByDay.png
pdf file
Data Taking Efficiency per Week
Same as above but per week.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/recEffByWeek.png
pdf file

Pileup Interactions - LHCP dataset

Number of Interactions per Crossing - LHCP Dataset
Shown is the luminosity-weighted distribution of the mean number of interactions per crossing for the 2015 pp collision data recorded from 3 June - 25 August at 13 TeV centre-of-mass energy (LHCP dataset). All data delivered to ATLAS during stable beams is shown, and the integrated luminosity and the mean mu value are given in the figure. The mean number of interactions per crossing corresponds to the mean of the poisson distribution of 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 80 mb for 13 TeV collisions, and fr is the LHC revolution frequency.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/mu_2015_lhcp.png
pdf file
eps file
Number of Interactions per Crossing - LHCP Dataset
Same as above, but with data delivered in fills with 50ns and 25ns bunch spacing shown separately.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/mu_2015_2550_lhcp.png
pdf file
eps file

Luminosity summary plots for 2015 pp data taking

These plots show the estimated integrated luminosity with the most recent offline calibration. (December 2015)

Total Integrated Luminosity and Data Quality in 2015
Cumulative luminosity versus time delivered to ATLAS (green), recorded by ATLAS (yellow), and certified to be good quality data (blue) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2015. 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 2015 EOYE Dataset DQ table here. The All Good Data Quality criteria require all reconstructed physics objects to be of good data quality. The IBL was turned off for two runs, corresponding to 0.2 fb-1 and analyses that don’t rely on the IBL can use 3.4 fb-1 of data with a corresponding DQ efficiency of 93.1%. The luminosity shown represents the preliminary 13 TeV luminosity calibration which was updated in December 2015.

The table corresponds to the DQ tag DetStatus-v73-pro19-08 with lumi tag OflLumi-13TeV-003.

https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/intlumivstime2015DQ.png
pdf file
For animations: delivered (png) delivered (pdf) recorded (png) recorded (pdf)
Total Integrated Luminosity in 2015
Cumulative luminosity versus time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2015. The delivered luminosity accounts for luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow for 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. Shown 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 13 TeV luminosity calibration which was updated in December 2015.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/sumLumiByDay.png
pdf file
Integrated Luminosity by Day in 2015
Integrated luminosity per day time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 13 TeV centre-of-mass energy in 2015. The data shown is identical to the data shown above, except not cumulative over the year.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/lumiByDay.png
pdf file
Peak Luminosity per Fill in 2015
The peak instantaneous luminosity delivered to ATLAS during stable beams for pp collisions at 13 TeV centre-of-mass energy is shown for each LHC fill as a function of time in 2015. The luminosity is determined using counting rates measured by the luminosity detectors, and is based on a preliminary 13 TeV calibration determined using van-der-Meer beam-separation scans.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/peakLumiByFill.png
pdf file
Peak Interactions per Crossing in 2015
The maximum number of inelastic collisions per beam crossing (µ) during stable beams for pp collisions at 13 TeV centre-of-mass energy is shown for each fill in 2015. The preliminary luminosity measurement is used to determine the number of interactions per beam crossing as µ = Lbunch x σinel / fr where Lbunch is the per-bunch instantaneous luminosity, σinel is the inelastic cross-section at 13 TeV, which is taken to be 80 mb, and fr is the LHC revolution frequency of 11.245 kHz. The number of interactions shown is averaged over all colliding bunch pairs, and only the peak value per fill during stable beams is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/peakMuByFill.png
pdf file
Luminosity Ratio for Different Algorithms
Fractional difference in run-integrated luminosity between the LUCID Bi_EvtORA algorithm, and the TILE, EMEC and track-counting algorithms. Each point corresponds to an ATLAS run recorded during 50 ns or 25 ns bunch-train running in 2015 at √s = 13 TeV. The luminosity measurements by TILE, EMEC and TRACKS have been normalized to LUCID in a group of physics runs recorded before the van der Meer calibration run on August 24th.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/LuminosityRatio_AllDetectors_Preliminary.png
pdf file
Luminosity Ratio for Different Algorithms
Fractional difference in run-integrated luminosity between the LUCID Bi_EvtORA measurement and the average of the values reported by the TILE, EMEC and track-counting algorithms. Each point corresponds to an ATLAS run recorded during 50 ns or 25 ns bunch-train running in 2015 at √s = 13 TeV. If one of more of the three detectors were not available the comparison uses the available detectors.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/LuminosityRatio_Average_Preliminary.png
pdf file
Luminosity Ratio for Different Algorithms
Fractional difference in run-integrated luminosity between the LUCID Bi_Evt_ORA and track-counting algorithms. Each point corresponds to an ATLAS run recorded during 50 ns or 25 ns bunch-train running in 2015 at √s = 13 TeV. Radioactive Bi-207 sources are used to monitor the gain of the photomultipliers in frequent calibration runs during the year. These pulse-height measurements are used to adjust the high voltage so that the gain remains constant throughout the year. In a second step, the Bi-207 calibrations are also used offline to correct the measured luminosity. The Figure shows the LUCID data before (red squares) and after the offline gain correction (black circles).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/LuminosityRatio_NoBiCorr_Preliminary.png
pdf file
Luminosity Ratio for Different Algorithms
Fractional difference in run-integrated luminosity between the LUCID Bi_Evt_ORA and track-counting algorithms. Each point corresponds to an ATLAS run recorded during 50 ns and 25 ns bunch-train running in 2015 at √s = 13 TeV. By the end of the data-taking period, the cumulative increase in high voltage that had been applied during the year to keep the photomultiplier gain constant, resulted in a significant decrease of the transit time through the photomultipliers. This, in turn, resulted in a loss of some events outside the timing window, and thereby in a decrease in detector efficiency. The impact of the transit time increase was different for different photomultipliers and was negligible for one of them. This photomultiplier was used to correct the luminosity measured by the others. The Figure shows the LUCID data before (red squares) and after the transit-time correction (black circles).
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/LuminosityRatio_NoTimeCorr_Preliminary.png
pdf file
Run-to-run Stability
Run-to-run stability of ATLAS luminometers for the 2015 proton-proton dataset at sqrt(s)=13 TeV, excluding dedicated low luminosity data taking periods. The calorimeter (Tile, FCal, EMEC) and track counting algorithms are cross-calibrated to a LUCID measurement of the integrated luminosity in the reference fill indicated by the arrow. Each point shows the mean fractional difference in integrated luminosity for a single ATLAS run, between the indicated algorithm and the reference LUCID luminosity algorithm. The plot demonstrates the relative stability of ATLAS luminometers at the +-2.5% level.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/OfficialPlots_Stability_ATLASStyle_py_PRELIMINARY.png
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van der Meer Calibration
Visible interaction rate for the LUCID algorithm (lucBiEvtA), that provides the ATLAS luminosity, in one bunch crossing and per unit bunch population, versus nominal beam separation during horizontal scan 1 in the August 2015 luminosity-calibration session. The total rate measured for a single colliding bunch pair at position 891 in the fill pattern is shown as red circles, and the background-subtracted rate as magenta squares. The background is dominated by random counts from the radioactive Bismuth source used for phototube gain calibration (blue triangles), as estimated from the rate measured in the preceding unfilled bunch slot. Also shown is the beam-gas background (green triangles) measured using non-colliding bunches. The background subtracted rate is fitted by a Gaussian multiplied by a sixth-order polynomial (dashed curve). The error bars are statistical only.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015/DataSummary/figs/lucBi_preliminary.png
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Luminosity summary plots for 2015 5 TeV pp data taking

These plots show the estimated integrated luminosity of the 5 TeV reference data with the online calibration.

Total Integrated Luminosity in 2015
Cumulative luminosity versus time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 5 TeV centre-of-mass energy in 2015. The delivered luminosity accounts for luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow for 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. Shown is the luminosity as determined from counting rates measured by the luminosity detectors. An online calibration based on Monte Carlo estimates has been used to set the luminosity scale.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015hipp/DataSummary/figs/sumLumiByDay.png
pdf file
Integrated Luminosity by Day in 2015
Integrated luminosity per day time delivered to (green) and recorded by ATLAS (yellow) during stable beams for pp collisions at 5 TeV centre-of-mass energy in 2015. The data shown is identical to the data shown above, except not cumulative over the year.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015hipp/DataSummary/figs/lumiByDay.png
pdf file
Peak Luminosity per Fill in 2015
The peak instantaneous luminosity delivered to ATLAS during stable beams for pp collisions at 5 TeV centre-of-mass energy is shown for each LHC fill as a function of time in 2015. An online calibration based on Monte Carlo estimates has been used to set the luminosity scale.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015hipp/DataSummary/figs/peakLumiByFill.png
pdf file

Luminosity summary plots for 2015 PbPb data taking

These plots show the estimated integrated luminosity of the PbPb collisions at 5 TeV per nucleon. The luminosity shown is a preliminary estimation based on van-der-Meer beam-separation scans.

Total Integrated Luminosity in 2015
Cumulative luminosity versus time delivered to (dark blue) and recorded by ATLAS (light blue) during stable beams for PbPb collisions at 5 TeV centre-of-mass energy per nucleon in 2015. The delivered luminosity accounts for luminosity delivered from the start of stable beams until the LHC requests ATLAS to put the detector in a safe standby mode to allow for 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. Shown 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/2015hi/DataSummary/figs/sumLumiByDay.png
pdf file
Integrated Luminosity by Day in 2015
Integrated luminosity per day time delivered to (green) and recorded by ATLAS (yellow) during stable beams for PbPb collisions at 5 TeV centre-of-mass energy per nucleon in 2015. The data shown is identical to the data shown above, except not cumulative over the year.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015hi/DataSummary/figs/lumiByDay.png
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Peak Luminosity per Fill in 2015
The peak instantaneous luminosity delivered to ATLAS during stable beams for PbPb collisions at 5 TeV centre-of-mass energy per nucleon is shown for each LHC fill as a function of time in 2015. The luminosity is determined using counting rates measured by the luminosity detectors, and is based on a preliminary calibration determined using van-der-Meer beam-separation scans.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015hi/DataSummary/figs/peakLumiByFill.png
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Peak Interactions per Crossing in 2015
The maximum number of inelastic collisions per beam crossing (µ) during stable beams for PbPb collisions at 5 TeV centre-of-mass energy per nucleon is shown for each fill in 2015. The preliminary luminosity measurement is used to determine the number of interactions per beam crossing as µ = Lbunch x σinel / fr where Lbunch is the per-bunch instantaneous luminosity, σinel is the inelastic PbPb cross-section at 5 TeV, which is taken to be 7.7 barns, and fr is the LHC revolution frequency of 11.245 kHz. The number of interactions shown is averaged over all colliding bunch pairs, and only the peak value per fill during stable beams is shown.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2015hi/DataSummary/figs/peakMuByFill.png
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Luminosity Measurement Based on Pixel Clusters (2016)

Typical distribution of the pixel-cluster size in the direction parallel to the beam axis, in the secondto-last forward inner layer (IBL) module
Typical distribution of the pixel-cluster size in the direction parallel to the beam axis, in the secondto-last forward inner layer (IBL) module. The IBL is a cylinder that consists of 14 azimuthal “staves”. Each stave contains 20 modules arranged along the beam axis and covers the pseudorapidity range |eta| < 3. The 12413 clusters that populate this plot originate from 10433 randomly-triggered events during ATLAS physics data-taking in 2015. The distribution is fit to the sum of a Gaussian signal (mean from fit is 9-pixels cluster length), plus an exponentially-falling background of shorter clusters. The Gaussian area is proportional to the number of charged particles originating from the luminous region and therefore proportional to the luminosity integrated during the approximately one-minute data-taking period. The exponential area contains contributions from secondary interactions and afterglow that will deviate from proportionality to luminosity, and is therefore treated as a background.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/fitplot.png
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Comparison of longitudinal cluster-size distributions for the four most forward modules
Comparison of longitudinal cluster-size distributions for the four most forward modules in an arbitrarily chosen inner layer (IBL) stave. The IBL is a cylinder that consists of 14 azimuthal “staves”, each of which contains 20 modules arranged along the beam axis and covers the pseudorapidity range |eta| < 3. The modules farther from the nominal collision point produce, on the average, longer clusters, while the shape of the falling background is approximately the same in all modules. This confirms that the length of signal clusters is sensitive to the particle incidence angle, as expected from simple geometrical arguments.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/DistPlot.png
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Afterglow in the IBL
During LHC operation, the IBL detector material is activated by pp collision debris. The resulting low energy decay products, collectively known as afterglow, induce delayed signals in the detector and produce single or small pixel clusters, thereby contributing to the background component of the cluster-length distributions rather than to the Gaussian-shaped long-cluster signal. The figure displays the bunch-slot dependence of the signal and background components, which correspond to, respectively, the area under the Gaussian curve and that under the falling exponential. These signal and background levels are extracted from fits to the cluster-length distributions from a forward IBL module, recorded in 8 consecutive 25 ns-long bunch slots. Only the first slot (numbered 2674) contained a colliding-bunch pair (and therefore a luminosity signal); the remaining 7 were nominally empty. The measured signal (Gaussian) component is largest in the first bunch slot, and drops by 4 orders of magnitude within 25 ns. The measured background (exponential) component, in contrast, decays much more slowly, with a time dependence suggestive of a mixture of radioactive decays. We have not attempted to identify those decays in this study.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/afterglow.png
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Azimuthal dependence of the long-cluster (Gaussian) signal for the forward-most modules of the IBL.
Azimuthal dependence of the long-cluster (Gaussian) signal for the forward-most modules of the IBL. The IBL is a cylinder that consists of 14 azimuthal staves, each of which contains 20 modules arranged along the beam axis and covers the pseudorapidity range |eta|<3. The sinusoidal dependence arises because in the plane perpendicular to the average beam direction, the luminous region is not perfectly centered on the IBL axis. In order to avoid being affected by occasional underperforming or noisy modules, the measured azimuthal dependence of the long-cluster signal is fit to the function A*cos((2*pi/14)*x + B)+C. Outliers are excluded from the fit on the basis of internal consistency. In this example, the 12th module was inefficient during the run considered; it was excluded form the fit based on its residual exceeding 4 sigma. The area under the fitted curve (rather than the sum of the 14 individual measurements) is used as a measure of the total number of signal clusters.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/phi_modules.png
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Time evolution, during an ATLAS run, of the longitudinal position of the luminous region
Time evolution, during an ATLAS run, of the longitudinal position of the luminous region either as determined from the average position of reconstructed pp-collision vertices (light blue circles), or as inferred from the forward-backward asymmetry of the pixel-cluster counts in the IBL (black squares). This asymmetry is computed from the long-cluster signals in the 4 outermost IBL modules on either side of the interaction point. It is sensitive to the longitudinal position of the luminous region because the acceptance of each module depends on its distance from the average collision point. The pixel-cluster-based luminosity measurement can be corrected for this geometric effect by using the beamspot position derived from the measured asymmetry of the pixel-cluster signal.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/location.png
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Time evolution, during an ATLAS run, of the pixel-cluster luminosity signal
Time evolution, during an ATLAS run, of the pixel-cluster luminosity signal normalized to the luminosity as measured by the ATLAS baseline luminometer (top), and of the RMS luminous length inferred from the longitudinal distribution of reconstructed pp-collision vertices (bottom). The luminosity-normalized pixel-cluster signal exhibits a similar time dependence to that of the luminous length, because the acceptance of each module depends on its distance from the corresponding interaction vertex. The pixel-cluster-based luminosity measurement must therefore be corrected for this geometric effect, using the luminous length derived from the longitudinal distribution of pp-collision vertices.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/sig_corr.png
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Comparison of the pixel-cluster counting (PCC) algorithm and the LUCID_EvtORA_Bi, TILE, and track-counting algorithms
Fractional difference in run-integrated luminosity between the pixel-cluster counting (PCC) algorithm and the LUCID_EvtORA_Bi, TILE, and track-counting algorithms, for the subset of ATLAS runs with 25 ns bunch spacing for which the PCC data are available. The absolute scale of the PCC-based luminosity is cross-calibrated to the luminosity from the comparison algorithm averaged over the runs taken from 11 to 13 September 2015.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/rat_pcc.png
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Fractional deviation of the bunch-averaged pile-up parameter average mu
Fractional deviation of the bunch-averaged pile-up parameter average mu, obtained using different algorithms, from the pixel-cluster counting (PCC) value, as a function of average mu during a physics run on September 25, 2015. The data are normalized such that all algorithms yield the same integrated luminosity in the run considered.
https://atlas.web.cern.ch/Atlas/GROUPS/DATAPREPARATION/PublicPlots/2016/Luminosity/rat_pcc_mu_zoom.png
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Major updates:
-- EricTorrence - 2015-07-20

Responsible: EricTorrence
Subject: public

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