Approved Transition Radiation Tracker Plots


The TRT detector commissioning and 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 TRT project leader in case of questions and/or suggestions.

See also ATLAS approval procedure of plots based on cosmic-ray and single-beam data and ATLAS publication guide. Since rootlogon.C script for the later is meant for papers, an updated version of rootlogon.C is uploaded to this twiki page. Essentially the only changes made are larger axis titles and labels. Please use this one and check for updates. If a common script is adopted at ID or ATLAS level, we will update this one accordingly.

For TRT SW, plots in preparation are shown here: TRTPlotsInPreparationForApproval. Once approved, they will be shown on this page.

Pictures - page in preparation.


Turn-on of Transition Radiation from Muons measured in the ATLAS Barrel TRT (Oct'2008)

Transition radiation TR is produced when a charged particle crosses the boundaries of two materials with different dielectric constants. The probability (intensity) of producing TR photons is depending on gamma (E/m) of the particle. The effect starts at gamma factors above 1000, thus essentially only for electrons in the typical energy range, and it is thus mostly used for identifying electrons. In the TRT, TR photons are detected by absorption of the photons in the chamber gas (Xenon mixture, short absorption length for photons) leading to high electronic pulses crossing a high threshold (pulses from particles which do not produce TR usually do only cross a low threshold).
On the plot one can see the turn-on of the production of TR photons as a function of gamma as measured for the tracks of cosmic particles (Muons) during cosmic data taking of the ATLAS detector in October 2008. On the y-axis the probability of a high-threshold hit (indicator for TR) is given.
The data points are shown for both muon charges (positive: red dots, negative: blue dots) and are compared to the results obtained in the ATLAS Combined Test Beam in 2004 (black line). The blue line gives a fit to the results obtained with the cosmic data, see description (details) below.
The turn-on of the Transition Radiation is nicely seen and the identical behaviour of the detector to cosmic tracks and data recorded at the test beam demonstrates that the TRT is working properly. The correspondence between mu+ and mu- is very good, and the results achieved with the barrel TRT and the endcap TRT also look much alike.

Cosmic tracks from runs 90272 and 90275 are required to have:
- Chi2/Ndof < 10.0
- NTRThits >= 20
- NSCThits >= 4
- pTerr / pT < 3.0
Finally, the pT has to be in the range [0.5,1000.0] GeV (for end points).
SCT hits are used to give the (th)eta of the track, and this requirement also greatly cleans up the sample. However, it reduces the 95000 tracks to 20000 (out of an original 140000).
After this, the events are asigned to bins in momentum (logarithmically), charge, and theta, and the hits are divided into barrel and endcap, after which the HT probabilities are calculated (as simple ratios).
The plots are then fitted with the logistic sigmoid function in log10 of the momentum (here x):
par[1] + par[2] / (1.0 + exp(-(log10(x) - par[3])/par[4]));
In the fit, par[2] is fixed to its expected value from CTB (about 0.16), since the cosmic data is not sensitive to the level of the high plateau, and out comes the two plots.
CLICK HERE TO DOWNLOAD LARGER PS-FILE: HTonsetFit_CosmicMuons_Barrel.eps Icon_HTonsetFit_CosmicMuons_Barrel.jpg
Turn-on of Transition Radiation from Muons measured in the ATLAS End-Cap TRT (Oct'2008)

The same figure as above for the Barrel TRT, however the results here were achieved with the End-Caps of the detector.

Concerning the production of transition radiation, the main difference between the Barrel and te End-Cap TRT are the different type of radiator materials. In the barrel, polypropylene-polyethylene fibre mats are used ("chaotic" orientation of fibres/boundaries) are used, in the end-caps polypropylene foils ("aligned" orientation of boundaries) serve as radiators.
Results achieved with the barrel TRT and the endcap TRT look very much alike.
CLICK HERE TO DOWNLOAD LARGER PS-FILE: HTonsetFit_CosmicMuons_Endcap.eps Icon_HTonsetFit_CosmicMuons_Endcap.jpg
Event with tracks from cosmic particles observed in the ATLAS TRT Barrel (Aug'2008)

This picture shows one of the first cosmic tracks recorded in the barrel TRT with the ATLAS solenoid being on. Small blue crosses indicate individual straw tubes of the barrel detector which have seen a signal. Particle tracks are nicely visible, low momentum particles even curl within the detector volume, reminding of bubble chamber photos. The event was taken in ATLAS Run 83585 and is displayed using a TRT monitoring tool, the TRTViewer.
The fraction of straws giving a signal which is not on a particle track (noise) is adjusted by the setting of the low threshold to be about 1%.
Event with tracks from cosmic particles observed in the ATLAS TRT End-Cap (Aug'2008)

Similar figure as described above for the barrel TRT but this time for one of the two endcaps.
On the x-axis the phi-sectors of the End-cap are given (32 in total), on the y-axis the different End-cap wheels are indicated (from bottom to top: 12 wheels of type A, short distance between detector layers, closer to the interaction point; 8 type B wheels with doubled distance between each layer of straws). The event was taken in ATLAS Run 83527 and is displayed using a TRT monitoring tool, the TRTViewer.
In sectors 9/10 two curling tracks can be seen - an electron-positron pair from a conversion?
This TRTviewer plot shows time over threshold (ToT), in ns (label % in the plot is wrong), for one of beam splash events, for TRT barrel side A. In beam splash events, there were many particles crossing each single straw. For that reason, leading edge signal (LE, coming from the electron that drifts for shortest distance) comes at the same time for all straws (assuming splash of particles is coming at the same time in different parts) and trailing edge is always invalid (TE, the signal continues outside the 3BC read-out window). Therefore, since ToT = TE - LE and TE is always 75ns, the plot effectively shows LE for different parts of barrel A. Since the tracks pass different parts of the detector at the same time, variances in the measured LE are actually only due to different signal propagation time (taken into account with T0 delay settings). Systematic pattern from top left to bottom right is because we used cosmic data to determine our current T0 delay settings and we did not correct for the time of flight - the effect of which can therefore be seen in this plot. Aside from that, you can see that the pattern is very uniform, confirming good accuracy of our T0 settings. Therefore, only one global transformation (that takes into account different time of flight in collisions compared to cosmic data) is needed for running with collisions.

Taken from Anatoli's presentation at Sept 15 2008 ID commissioning meeting
TRT Barrel Resolution

This plots is made with TRTonly tracks (from CTB), with the following requirements:
-no minimum pT requirement
- D0 < 100 mm (through pixel)
- min 45 TRT hits
- Reject tracks with endcap hits
- Reject tracks that come from events with more than one reco CTB track (< 5 % of events, avoids pattern reco mistakes )

The fit is a sum of two gaussians, one fit to the core and one fit to the tails, the mean and sigma of the core are reported. The tracks are for the run 91800 (run with magnetic field).

Provided by John Alison (alignment monitoring)

Difference in $\phi_0$ of tracks from cosmic ray data which are split into upper and lower halves. Tracks that were split were required to have at least 2 Pixel hits, 9 SCT hits, 45 TRT hits, and have a minimum $p_T$ of 2 GeV. The black distribution is before a relative TRT-SCT alignment and blue is after.
The quoted numbers are the result of the Gaussian fit shown. The entire range of each distribution was fit with a Gaussian, and then a second fit was done in the range meanFirstFit +/- 1.5 * sigmaFirstFit. It is the result of the second fit that is shown and quoted.
Provided by John Alison (alignment monitoring)
Figure description ... [the figure]
Figure description ... [the figure]


Responsible: TRT Project Leader
Last reviewed by: Never reviewed

  • deltaPhi.png:

  • rootlogon.C: rootlogon for presentation plots (based on ATLAS rootlogon)
Topic attachments
I Attachment History Action Size Date Who CommentSorted ascending
Unknown file formateps deltaPhi.eps r1 manage 32.7 K 2009-02-27 - 17:21 JohnAlison  
PNGpng deltaPhi.png r1 manage 19.2 K 2009-02-27 - 17:25 JohnAlison  
JPEGjpg run83585_TRT-Barrel.jpg r1 manage 172.1 K 2008-10-16 - 18:23 ChristophRembser One of the first TRT Barrel events with ATLAS magnetic field on
JPEGjpg run83527_TRT-EndCap.jpg r1 manage 287.6 K 2008-10-16 - 17:51 ChristophRembser One of the first TRT End-Cap events with ATLAS magnetic field on
Unknown file formateps HTonsetFit_CosmicMuons_Barrel.eps r1 manage 15.6 K 2008-10-16 - 19:14 ChristophRembser Onset of high threshold probability for cosmic particles / Barrel TRT
Unknown file formateps HTonsetFit_CosmicMuons_Endcap.eps r1 manage 15.9 K 2008-10-16 - 19:16 ChristophRembser Onset of high threshold probability for cosmic particles / End-Cap TRT
C source code filec rootlogon.C r1 manage 2.5 K 2009-03-12 - 16:53 SasaFratina rootlogon for presentation plots (based on ATLAS rootlogon)
Unknown file formateps TRTBarrelResidual.eps r1 manage 23.0 K 2009-02-03 - 17:52 SasaFratina TRT barrel residuals, eps, same as png
PNGpng TRTBarrelResidual.png r1 manage 16.5 K 2009-02-03 - 14:20 SasaFratina TRT barrel residuals, result of alignment monitoring, temporary plot
PNGpng beamSplashBarrelA.png r1 manage 179.6 K 2008-12-04 - 23:06 SasaFratina TRTviewer plot of time over threshold (in ns) for beam splash event, barrel A
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Topic revision: r12 - 2009-04-09 - SasaFratina
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