Approved Combined Inner Detector Plots

Detector alignment

Description: The plot show TRT residual distribution from cosmic data with the solenoid on (run 91900). Tracks are required to have pT >2 GeV, event phase between 5 and 30 ns, >= 45 TRT hits, >= 2 Pixel hits, >= 9 SCT hits, and no endcap hits. A single Gaussian fit to the core of the distribution (+/- 0.3 mm) is done, and the mean and sigma of the fit are reported. The distribution is made in athena release 15 (-tag=15.0.0) and using ID alignment tags InDet_Cosmics_2008_03 and TRT_Cosmics_2008_06.

ID track parameter resolutions

The following cuts have ben applied per track (if not stated otherwise):

• nPixelHits in the barrel >=2
• nSCTHits in the barrel >=6
• nTRTHits in the barrel >=25
• |d0| < 40mm
• pT >= 1 GeV

Additionally only events with an event phase between 5 and 30 ns are accepted to ensure proper timing of the sub-detectors. The plots show comparisons of tracks using the full Inner Detector (silicon and TRT detectors, closed triangles), only the silicon sub-detecors (open triangles) together with tracks from cosmic simulation using the full Inner Detector (stars). The requirement of at least 25 TRT hits is dropped for silicon only tracks. However, the cut on the event phase is retained to ensure proper timing and the comparability of the analyzed sets of tracks. There is no cut on the event phase for simulation events since the jitter in cosmic trigger timing is not simulated.

Distributions from cosmic ray tracks

Warning: Cosmic ray spectra including comparisons with MC which appeared before on this page are not approved for external use at this stage. The MC does not model some details of the special cosmic trigger configuration and timing. It includes the two main access shafts, but not the two lift shafts. Until these effects are taken into account, the MC-data comparison is not useful.

Cosmic muons crossing the entire ATLAS detector leave hits in the Inner Detector (ID) and so tracks can be reconstructed. Two different tracking algorithms are in use for the reconstruction: the CTB (Cosmics and Test Beam) tracking and the New Tracking. The results below show the performance of the CTB.

Tracks are characterized by 5 parameters. These are defined in a reference point, the perigee, which is the point of closest approach to the z/beam axis. d0 is the signed distance to the z-axis, z0 is the z-coordinate of the perigee, phi0 is the angle in the x-y plane at the perigee, theta0 is the angle with the z-axis and q/p is the charge of the cosmic muon divided by its momentum.

In the next plots, the parameters of these cosmic muon tracks (reconstructed with CTB tracking and release 14.5.0.5, AtlasProduction) from the ATLAS combined cosmic run 91890 (Autumn 2008) are shown. Both toroid and solenoid were on during this run.

For the theta0 and z0 distributions, tracks are required to have Silicon hits (since these parameters are not measured by the TRT barrel).

Cosmic ray track statistics

Event displays

Beam Conditions Monitor (BCM) timing distributions

During the combined Inner Detector running in November 2008, out of 50 million triggers, over 100 events with signals in the BCM were observed. The BCM reads out 31 consecutive bunch crossings for each trigger, and the initial timing calibration from measured cable and fibre lengths puts the signal around bin 19. The timing distribution is narrower for events triggered by the TRT than for events triggered by the RPC muon chambers.

Comparison of NewTracking and CTBTracking

The following cuts have ben applied:

• 2*nPixelHits+nSCTHits>=8
• number of TRT hits >=40
• pT >= 5 GeV