Combined Muon Performance Public Plots from Cosmic-Ray Data

Introduction

The combined muon performance plots below are approved to be shown by ATLAS speakers at conferences and similar events.

Please do not add figures on your own.
Contact the the muon combined performance coordinators (atlas-perf-muons-conveners@cernNOSPAMPLEASE.ch) in case of questions and/or suggestions.

Plots from first reprocessing of cosmics 2008 data

The plots show, on cosmic data from autumn 2008, the comparison between quantities reconstructed for inner detector tracks and for matching muon spectrometer ones. The observed differences are in agreement with the expected multiple scattering and energy loss in the calorimeters and are well reproduced by the Monte Carlo simulation. No correction has been yet applied for the relative alignment of the two subdetectors, which appears to be already quite good.

The plots were obtained using 18k data events from ATLAS combined cosmic run 91890, taken with both solenoid and toroid fields on. These events, produced by the December 2008 re-processing at Tier1's, were pre-selected requiring a reconstructed track in the Inner Detector (ID). Simulated events use the latest samples available at the time, made with release 14.4.0. One of the main improvements with respect to previous simulations was the use of the Xe-gas mixture for the transition radiation tracker (TRT) and an updated detector description geometry. The relevant parts of the reconstruction chain were re-run with release 14.5.0.5, with a special fix for an incorrect drift function also used for the simulated data. In addition, one RPC sector (6) was masked in simulation, corresponding to the real detector configuration in the run analysed.

The following event selection was applied in order to emulate the stream and trigger configuration used:

• At least one track reconstructed in the ID.
• At least one combined ID-MS reconstructed track with 3 or more RPC Phi hits.

After all these cuts, the number of events in the analysis is:

• Real data: 4.8k events (initially 18k)
• Simulated data: 6k events (initially 10k).

Tracks reconstructed by MOORE and CTB trackers in the MS and ID respectively were used for this analysis. No global ID-MS alignment corrections were applied in the reconstruction.

Next, the track parameters at perigee are compared between MS and ID standalone reconstructions. Except the momentum, MS track parameters are extrapolated to the beam axis (taking into account the energy loss in the calorimeters) in order to allow for comparisons. Next, the track parameters at perigee are compared between MS and ID standalone reconstructions. In order to compare Theta0 and z0 parameters, ID tracks are required to have Silicon hits.

An internal note with some more technical details on the reconstruction is available, for ATLAS members only, at ATL-COM-PHYS-2009-074.

Correlation between Muon Spectrometer (MS) and Inner Detector (ID) track parameters [Run 91890]: Phi0 correlation. The good correlation observed between parameters measured in the MS and ID shows that both sub-detectors are well synchronized. eps version
Correlation between Muon Spectrometer (MS) and Inner Detector (ID) track parameters [Run 91890]: Theta0 correlation. The good correlation observed between parameters measured in the MS and ID shows that both sub-detectors are well synchronized. eps version
Difference between Muon Spectrometer (MS) and Inner Detector (ID) standalone reconstruction [Data/MC comparisons]: Phi0 parameter. The differences between the track parameters measured in the MS and the ID gives an idea about how well both sub-detectors are mechanically aligned. The agreement data/MC is fairly good. eps version
Difference between Muon Spectrometer (MS) and Inner Detector (ID) standalone reconstruction [Data/MC comparisons]: Theta0 parameter. The differences between the track parameters measured in the MS and the ID gives an idea about how well both sub-detectors are mechanically aligned. The agreement data/MC is fairly good. eps version
Difference between Muon Spectrometer (MS) and Inner Detector (ID) standalone reconstruction [Data/MC comparisons]: d0 parameter. The differences between the track parameters measured in the MS and the ID (QoverP distribution available for the Inner Detector approved plots page) gives an idea about how well both sub-detectors are mechanically aligned. The agreement data/MC is fairly good. eps version
Difference between Muon Spectrometer (MS) and Inner Detector (ID) standalone reconstruction [Data/MC comparisons]: z0 parameter. The differences between the track parameters measured in the MS and the ID gives an idea about how well both sub-detectors are mechanically aligned. The agreement data/MC is fairly good, within 4mm. eps version
By taking the difference in the momentum measured in the ID and MS, one can study the energy loss in the calorimeters. The plot shows this difference between ID and bottom MS tracks. A mean value of about 3 GeV is observed for both data and MC. eps version

Plots from fast reprocessing of cosmics June-July 2009 data

We compare the momenta measured by the tracking devices (inner detector and muon spectrometer) with the energy measured by the calorimeters (LArEM and Tile) and the energy deposited around muon tracks for an isolated muon sample. Cosmic-ray data from june 2009 was used, from the official ATLAS processing. these plots were approved on 15/1/2010.

Calorimetric isolation: sum of transverse energy around muon tracks for cones of dR = 0.2, 0.3 and 0.4 (eps file)
Momentum difference between Inner Detector and Muon Spectrometer tracks compared with the energy loss measured in the calorimeters, and a parametrization of the energy loss in the inert material. (eps file)
Subtraction of the momentum difference between Inner Detector and Muon Spectrometer tracks, and energy loss measured in the calorimeters, corrected by a parametrization of the energy loss in the inert material, for two momentum ranges: 10 < p_ID < 25 and 5 < p_ID < 500 GeV. (eps file)

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Major updates:
-- DomiziaOrestano - 09 Mar 2009 -- DomiziaOrestano - 27-Jan-2010

Responsible: DaveCharlton
Last reviewed by: Never reviewed