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Approved plots that can be shown by ATLAS speakers at conferences and similar events. Please do not add figures on your own. Contact the Data Preparation Coordinators in case of questions and/or suggestions.  
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Instantaneous luminosity determined by two independent methods for run 142193, taken by ATLAS on Dec 12, 2009. This run offered an extended stablebeam period of 4.5 hours, thus allowing ATLAS to measure the instantaneous luminosity for varying beam intensities. The blue open circles show the instantaneous luminosity as determined by the LAr and the red triangles show the instantaneous luminosity as measured by the MBTS. The 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. For these measurements the PYHTIA Monte Carlo simulation of the pp inelastic processes have been used. The corresponding cross section used to normalize the measurements is 52.5 mb including nondiffractive, singlediffractive, and doublediffractive processes. The systematic uncertainty on the model is estimated using PHOJET. The difference between the two models translates into a variation of the luminosity of 18% for LAr and 15% for the MBTS. This uncertainty is 100% correlated between the two methods and dominates the total uncertainty on the measurements. The two curves show only the statistical error as the systematic uncertainty is time independent. For this run the estimated delivered luminosity is 3.0± 0.6μb^{−1}:  
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> >  EPS version
 
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Systematic uncertainties of the two methods currently used for the luminosity measurements.
The correlation coeffcient is 100%. Note, that the total systematic error is not the quadratic sum of
the individual ones in all cases since part of the detector response is correlated to the uncertainty on the
accceptance.
 EPS version 
Rate of events in LHC Fill 911 with at least one charged primary particle (p_{T} >0.5 GeV/c, η<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 1.08 +/ 0.02. It corrects for any experimental
efficiencies, e.g. due to the tracking, vertexing and trigger efficiencies.

eps file 
Cross sections and acceptances of the requirement of have at least one charged primary particle with
η<0.8 and p_{T} >0.5 GeV/c for two Pythia Monte Carlo tunes, for Pythia 8 and for
Phojet for √s=900 GeV. The statistical uncertainties on the numbers given are less than 0.1\%.


The assumed cross section model, the acceptance model, the visible cross section (σ_{vis})
and the ratio of the visible to the total inelastic cross section
is given where σ_{inel}=σ_{ND}+σ_{SD}+σ_{DD}
for √s=900 GeV.


Instantaneous Luminosity for LHC fill 911 vs UTC time comparing three methods of luminosity determination. The "Track" based method (solid circles) measures the
luminosity by counting primary charged particles with p_{T} > 0.5 GeV/c and η<0.8. The "MBTS" method (open circles) counts events that have energy deposits on both
sides of the interaction point in the MBTS scintillators in the range 2.09<η<3.84 that are consistent in timing with a collision event. The "LAr Timing" method (open circles)
counts events that have energy deposits on both sides of the interaction point in the LAr calorimeter in the range 2.5<η<4.5 that are consistent in
timing with a collision event. For all methods the visible cross section is determined using Pythia MC09 for the model of inelastic collisions.
The Track based method gives an 3% larger luminosity than the MBTS method and a 7% larger luminosity than the LAr method. The MBTS (LAr) method has a systematic
uncertainty of 4% (5%) that is uncorrelated with the Track method, while the uncorrelated systematic uncertainty of the Track Counting method is 2%. 
eps file 
The instantaneous luminosity for LHC Fill 911 as a function of UTC time. The luminosity is shown assuming the
Pythia (black solid markers) vs the Phojet (blue histogram) model for the acceptances and the cross sections. 
eps file 
 
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EPS version  
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> > 
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> > 
 
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< <  The plot shows the performance of the LAr, LUCID zero counting AND, and the HLT vertex
counting normalized to give the same integrated luminosity as the MBTS results. The MBTS (shaded
area) result provides the ATLAS luminosity. It is corrected for the dead time in the data acquisition
system, and is therefore an estimate of the LHC delivered luminosity at the ATLAS interaction The
corresponding cross section used to normalize the measurements is 52.5 mb includes nondiffractive,
singlediffractive, and doublediffractive. The systematic uncertainty in the model is estimated using
PHOJET. The difference between the two models translates into a variation of the luminosity of 15%. For
this run the estimated delivered luminosity is, 3.0± 0.6μb^{−1}: the uncertainty is dominated by
the systematic on the physics model. The LUCID zero counting AND is not corrected for the dead time
in the data acquisition system since the LUCID detector is not exposed to this effect. The four curves
show only the statistical error as the systematic uncertainties are time independent and largely correlated
among the different methods.
 
> >  The luminosity was measured using the forward LiquidArgon calorimeters. The acceptance of the selection was taken from
pythia as described above. The specific luminosity is given by the instantaneous luminosity divided by the number of protons per bunch in each of the beams
and the number of colliding bunches. The number of protons per beam is taken from TIMBER.
eps files are also available for the spec. luminosity for fill 911, fill 919, fill 923 and for the IP separation plot  
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< <  The plot shows the performance of the LAr, LUCID zero counting AND, and the HLT vertex
counting methods. The LUCID and the HLT are normalized to give the same integrated luminosity as the
MBTS results, while the LAr is normalized using its own visible cross section.
The MBTS (shaded area) result provides the ATLAS luminosity. It is corrected for the
dead time in the data acquisition system, and is therefore an estimate of the LHC delivered luminosity
at the ATLAS interaction The lower luminosity bin around 14:30 UTC includes a period of time where
ATLAS was 100% busy and therefore it is not possible to derive a deadtime correction. The LUCID zero
counting AND is not corrected for the dead time in the data acquisition system since the LUCID detector
is not exposed to this effect. For this reason LUCID does not show the deep at around 14:30 UTC. The
corresponding cross section used to normalize the measurements is 52.5 mb includes nondiffractive,
singlediffractive, and doublediffractive. The systematic uncertainty in the model is estimated using
PHOJET. The difference between the two models translates into a variation of the luminosity of 15%. For
this run the estimated delivered luminosity is 3.0± 0.6μb^{−1}: , the uncertainty is dominated
by the systematic on the physics model. The four curves show only the statistical error as the systematic
uncertainties are time independent and largely correlated among the different methods.
 
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When the stable beam flag is raised, the inner detector and muon systems undergo a socalled "warm start", which includes a ramp of the highvoltage and, for the pixel system, the preamplifiers are turned on. This procedure takes typically several minutes, which, in case of short stable beam periods, sums up to a significant fraction. This dominates the quoted inefficiencies. Longer runs and automation of the warm start will help to reduce the inefficiency.  
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< <  PNG version of table  
> >  PDF version of table  