ATLAS Combined Testbeam - 2004 Muon Detector – Calorimeter combined reconstruction

1. ATLAS Combined Testbeam - 2004Muon Detector – Calorimeter combined reconstruction K.Bachas*, Ch.Petridou*, D.Sampsonidis * R.Nicolaidou**, J.F.Laporte** *Aristotle University of Thessaloniki **Saclay Muon Software Group

2. Outline • Reminder of the ATLAS H8 Testbeam setup in 2004 • Motivation for this study • Track reconstruction in a muon tracking chamber - MDT • Combined results with Calorimeters • Summary

3. Combined Testbeam final configuration Iron Dump Barrel setup (2 towers MDT+RPC) EndCap MDT setup CSC BIS chamber Rotating BIL BOS MDT+RPC station TGCs Magnets • Pixel, SCT, TRT • LAr, Tile • 15 MDTs, 7 RPCs, 3 TGCs, 1 CSC

4. BIS in H8 Combined TestBeam • BIS type Monitored Drift Tube Muon chamber • Consists of 8 layers of tubes • Constructed in Greece by the Greek ATLAS Muon Collaboration • Installed in October 2004 • Participated in October-November runs at H8, electron and muon beams • BIS was placed in front of the LAr Calorimeter and was fixed to the Calorimeter’s table (see next slide) • Position of BIS varied with Calorimeter table movements. • Tube direction (y) not vertical to beam axis (x).

5. LAr Cryostat TRT BIS Y (tube) X (beam) Rotation of BIS around z axis by 11.5 degrees Z (to counting room)

6. Aim of study • Liquid Argon Calorimeter Community • Measure the absolute size of the calorimeter that is the thermal contraction of the electrodes from room temperature to 90 K (expected to be around 7mm) • Muon Community • Reconstruct track segments in one chamber alone – non ATLAS like configuration - No second coordinate information • Challenging beam environment • e and µ beams, normal flux 6K/spill , high flux 47K/spill • high beam contamination – yields several tracks in the event • Reconstruct tracks at steep beam incident angles

7. Analysis • 4 e+ runs at different calorimeter table positions at beam E=180GeV • 2 μ runs at same table positions at beam E= 350 GeV • Huge beam contamination • Apply selection criteria to select only desired particle type • Positrons: ETile < 2 GeV and ELar > 150 GeV • Muons: ETile < 3 GeV and ELar < 1.5 GeV Muon run Positron run E_Tile (GeV) E_Tile (GeV) e+ μ E_LAr (GeV) E_LAr (GeV)

8. Analysis- Track segment reconstructionProblems encountered Drift Time shift 200ns • DriftTime calculation did not take into account BIS specific trigger time corrections – shift in drifttime by 200 nsec • The DriftTime – Distance relation (R-t) was taken from the other chambers of the Testbeam. • Residuals: The difference between the actual distance of the track from the wire calculated from R-t and the distance of the reconstructed track from the wire • Cabling map used during reconstruction was wrong nsec Residuals vs Radius 200 µm before after mm

9. Analysis- Muon track segment reconstruction • Reconstructed track segments for muons • Select “good” track segments with the following criteria: • Keep only the best segment from each event • Select the one with the highest number of hits (at least 6) Segments per event Hits per segment Number of segments Number of hits Residuals of good segments RMS ~164 µm

10. Analysis- Positron track segment reconstruction • Reconstructed track segments for positrons • More segments per event with fewer hits – positrons radiate in the material • Select “good” track segments with the same criteria as before • 4 positron runs at different rapidities Segments per event Hits per segment Number of segments Residuals of good segments Number of hits RMS ~190 µm

11. BIS – LAr Correlations LAr BIS • Obtain from BIS 4 angles and 4 beam positions • Extrapolate tracks to the LAr middle compartment • Correlate Z position of the track of BIS with eta position of the cluster barycenter • Compute the angle between BIS and LAr • Compute the parameter e for LAr electrodes

12. BIS – LAr Correlations LAr Cluster Eta Segment Z coord (mm) • From the 4 positron runs with different incident angles (α, β, γ, δ) we obtain the correlation between the eta of the barycenter of the LAr cluster in the middle compartment and the track’s position in the precision coordinate (Z).

13. Summary • This analysis will be concluded by calculating from the fit to the correlations the BIS-LAr relative angle and the absolute size of the calorimeter. • This “exercise” has demonstrated that even in challenging conditions (intense beams, steep incident beam angles) we can still reconstruct track segments in muon chambers and combine them with calorimeter information. • Testbeam combined analysis has been proven an excellent “warm-up” for the ATLAS physics analysis race!