Invariant mass resolution for combined muons with 205 pb-1
- Di-muon invariant mass distribution for oppositely charged muon pairs with transverse momentum above 20 GeV and calorimeter isolation (sum of calorimeter cell energies <2 GeV in a cone of ΔR=0.3.).
- Both muons are restricted to |eta|<2.5.
- Collision events are selected from event filter triggers of 20 GeV threshold.
- The momentum vector is jointly reconstructed in the muon spectrometer and the inner tracking detector (“combined muon”).
- The measured di-muon mass is compared to Monte Carlo prediction using Pythia generated Z->µµ events.
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eps file |
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Muon reconstruction efficiencies dertermined Z->μμ decays at 7 TeV |
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Improvement to the invariant mass resolution with the November data reprocessing
- Dimuon event selection like above.
- The muon momenta are measured by the muon spectrometer only and corrected for the energy loss of the muons in the calorimeter.
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eps file |
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Di-muon invariant mass distribution for 40.0pb-1 at 7 TeV |
Di-muon invariant mass spectrum
Di-muon invariant mass spectrum for data, from fully combined opposite sign muons in EF_MU15 triggered events. The muon Event Filter trigger applies a pT threshold at ~15GeV, which for consistency is reconfirmed offline for one of the two inner detector-muon spectrometer combined tracks (the other one is required to pass a p_T threshold of 2.5 GeV).
The plot shown corresponds to an integrated luminosity of about 40 pb−1.
Differences to the previous plots arise mainly from the use of a high trigger threshold and from plotting the event density in each bin.
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eps file |
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Di-muon invariant mass distribution for 3.0pb-1 at 7 TeV |
Di-muon invariant mass spectrum
Di-muon invariant mass spectrum for data, from fully combined opposite sign muons in L1_MU6 triggered events. The muon trigger applies a p_T threshold at ~6GeV, while the two inner detector-muon spectrometer combined tracks have a p_T threshold of 4 and 2.5 GeV respectively.
The plot shown corresponds to an integrated luminosity of about 3.0 pb−1.
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eps file |
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Di-muon invariant mass distribution for 330nb-1 at 7 TeV |
Di-muon invariant mass spectrum
Di-muon invariant mass spectrum for data, from fully combined opposite sign muons in L1_MU6 triggered events. The muon trigger applies a p_T threshold at ~6GeV, while the inner detector-muon spectrometer combined tracks have an effective p_T threshold of ~4GeV in the barrel, which decreases at high pseudo-rapidity. No explicit selection on muon p_T is applied.
The plot shown corresponds to an integrated luminosity of 330 nb−1.
Plot prepared for and presented at ICHEP 2010. Kept for reference. For more recent talks please use the 3.0 pb−1 distribution.
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eps file |
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Di-muon invariant mass distribution for 320µb-1 at 7 TeV |
Di-muon invariant mass distribution for 320µb-1 at 7 TeV using minimum bias trigger
- Di-muon invariant mass distribution for oppositely charged muon pairs with an energy above 3 GeV each: calculated from inner detector track parameters after fit to a common vertex.
- At least one muon must be jointly reconstructed in the muon spectrometer and the inner tracking detector (“combined muon”).
- The fit to the distribution is an unbinned maximum likelihood fit, using event-by-event errors calculated for each di-muon:
Gaussian-mean mass: 3.06±0.02 GeV Resolution: 0.08±0.02 GeV Number of signal events: 49±12 Number of background events: 28±4
- The mass region shown in the plot is fitted. Signal and background are computed in a mass range: 2.82-3.30GeV (3 σ around the peak).
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eps file |
Preliminary Figures from 2009 Collision Data at 900 GeV
Figures for runs 142171, 142174, 142189, 142191, 142193, 142195, 142383 (TOROID ON)
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The Solenoid field was on. The Toroid field was raised to nominal value during run 142171.
As a consequence only the last Luminosity Blocks of that run are considered here. |
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The Luminosity Blocks used were obtained requesting safe beams from LHC and all the
relevant detectors (MDTs, RPCs, TGCs, Pixels, SCT, TRT) to be operated at nominal HV.
Also the level 1 central trigger processor and DAQ status were checked to be good.
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Collisions were selected considering only paired Bunch Crossing Identifiers and through the timing of MBTS or LAr
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Only events with at least 3 tracks in Inner Detector, with at least 1 Pixel hits and 6 SCT hits,
and with one track with p > 4 GeV, were considered |
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Tight cuts on the muon candidates were applied requesting a confirmation in the Inner Detector for all of them |
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Results shown here are for the muon candidates with p > 4 GeV, pt > 2.5 GeV and
abs(eta)<2.5 (50 candidates) and are compared to the non-diffractive Minimum bias MC
normalized to the number of entries |
Parameter distributions in Data and Simulation |
Azimuthal angle distribution for muon candidates
The anglular track parameter is measured by the Inner Detector.
The distribution is flat in Φ, as expected for collisions.
eps file
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Pseudorapidity distribution for muon candidates
The pseudorapidity is measured by the Inner Detector.
Distribution peaked at large η, as expected for minimum bias p-p collisions
eps file
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transverse momentum distribution for muon candidates
The transverse momentum is measured by the Inner Detector.
eps file
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momentum distribution for muon candidates
The momentum is measured by the Inner Detector.
eps file
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Figures for runs 141749 and 141811 (TOROID OFF)
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The toroid magnets, which bend the muon tracks in the z projection,
were OFF for runs 141749 and 141811, so the muons follow a straight
path and the momentum is not measured in the spectrometer. |
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However, the acceptance is increased due to the fact that even very
low momentum muons can traverse the spectrometer. |
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Cathode Strip Chambers are not yet included in the runs 141749 and 141811 |
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*Event Selection and Data Sets*
cut description |
Numbers of events passing runs 141749 and 14181 |
Coincidence in MBTS (Min-bias trigger) and LAr timing |
8k + 20k |
Good luminosity block and BCID per run Run 141749: LB 23-102 BCID:1, 899, 2674 Run 141811: LB 126-165 activity in the muon spectrometer |
2022 |
ID Selection criteria P(ID) > 3 GeV at least 3 ID tracks with N(Pixel+SCT)>5 |
124 |
Combined and Standalone tracks with trigger chamber hits (RPC, TGC) |
83 |
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Responsible: atlas-perf-muons-conveners@cernNOSPAMPLEASE.ch
Last reviewed by: Never reviewed
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