1. The Detector Performance Study for the Barrel Section of the ATLAS Semiconductor Tracker (SCT) with Cosmic Rays Yoshikazu Nagai, Kazuhiko Hara (Univ. of Tsukuba) Yoshiki Yamashita, Ryuichi Takashima （ Kyoto Univ. of Education ） Satoru Mima, Reisaburo Tanaka （ Okayama Univ. ） Taka Kondo （ KEK ）

2. Contents Introduction Large Hadron Collider (LHC) & ATLAS ID Barrel Combined Cosmic Ray Test SCT Analysis Track reconstruction SCT Module Efficiencies High Resistance Modules Summary and Plans

3. Large Hadron Collider (LHC) physics motivations Higgs physics Physics beyond the SM Supersymmetry Extra dimension etc … Many other physics … ALICE MONT BLANC Lac Léman Geneva Air Port LHCb CMS ATLAS 8.5km LHC （ Large Hadron Collider) @ CERN First collision will be in November 2007 with. The collisions with will be in April 2008. LHC is a proton-proton collider which is under construction @ CERN.

4. Inner Detector Pixel : the pixel detector SCT : the semiconductor tracker TRT : the transition radiation tracker Calorimeter Muon Systems Magnet systems A Toroidal LHC ApparatuS (ATLAS) Tile HD LAr EM LAr HEC Muon Systems 42m 23m Magnet systems Overall weight : 8000 Tons Tracker : Calorimeter :

5. ID Barrel Combined Cosmic Ray Test # of Modules =468 (Top=252, Bottom=216) (layer 0,1,2,3) = (84/108/144/132) layer 0 layer 3 layer 1 layer 2 Top Bottom S3 S2 S1 trigger: or No magnetic field 12 modules Link0 Link1 TRT SCT

6. ID Barrel Combined Cosmic Ray Test First combined test of ID with realistic geometry Goals of combined cosmic ray test Test SCT 4 barrels with operating TRT Check detector efficiency, noise level, alignment study, tracking study Develop monitoring tools for SCT/TRT etc …

7. Event Info SCT + TRT Combined Run # of Events : 110K Track Reconstruction Spacepoint is formed by finding the intersection of the strips on the front and back side of a module Track candidates are built by fitting these spacepoints with straight-line (pattern finding procedure) SCT Spacepoint definition Track Reconstruction (with no alignment) Tracks are reconstructed in ATHENA (ATLAS software) flame work. track candidate

8. Track Reconstruction if track candidates are found Track candidates are fitted by hits (single or a few strips) (fitting procedure) SCT Hit difinition strip fired if track has chi^2 / ndof < 40, it is accepted !! (Here, tracks are roughly cut) 1 module track For accepted tracks remove one layer hits (e.g. remove hits in layer 0) refit the track if refitted track fills : chi^2 / ndof < 10 & Hits in Top sector >4 & Hits in Bottom sector > 4 this track is used for efficiency caluculation muon remove hit

9. Efficiency Caluculation strip fired predicted hit position 1.5mm Hit Observed !! extrapolate the refitted track to the layer surface which hits removed = predicted hit position search hits from the predicted hit position within 1.5mm = observed hit or not black : real data red : sim data chi^2 / ndof mm Efficiency Eff = # of observed hit / # of predicted hit real data sim data

10. SCT Module Efficiencies real data sim data layer 0 Link1layer 1 Link0layer 0 Link0layer 2 Link0layer 1 Link1layer 2 Link1layer 3 Link0layer 3 Link1 layer 0 Link1layer 1 Link0layer 0 Link0layer 2 Link0layer 1 Link1layer 2 Link1layer 3 Link0layer 3 Link1 real data shows ~ 99% Efficiency sim data shows ~ 95% Efficiency Both sim & real data show low Efficiency in Layer 3 What are the inefficiency sources ??

11. SCT Module Efficiencies real data sim data layer 3 Link 0 layer 3 Link 1 cable swap some bottom sector modules shows low Efficiency !!

12. top RMS :0.0311 Mean :0.9719 bottom RMS :0.0488 Mean :0.8852 real data sim data Efficiency / 0.5% normalize top RMS :0.0332 Mean :0.9808 bottom RMS :0.0842 Mean :0.9627 Layer 3 Module Efficiencies top vs bottom

13. High resistance in HV bias line are found in ID barrel cosmic test Statistics Out of 468 SCT barrel modules for ID barrel cosmic test 46 Modules have R>40k  28 Modules have R>40k  after 100-10  A cycle. 4 Modules have R>100k  after 100-10  A cycle. normal SCT modules should have R = 35 ~ 40k  resistance through the bias voltage circuit High resistance modules

14. 46 Modules have R>40k  Resistance (kOhm) High resistance modules

15. Efficiency / 0.5% Red Line : R>40kOhm modules (46modules) Black Line : R<40kOhm modules RMS : 0.0973 Mean : 0.9656 RMS : 0.0252 Mean : 0.9861

16. Summary module efficiency for layer 0,1,2 show ~ 99% with cosmic ray. module efficiency for layer 3 show ~ 98.2%, a bit lower than other layers. layer 3 top sector efficiency is a bit higher than bottom sector. modules with high resistance show the possibility of efficiency degradation. Plans check what the layer 3 module inefficiency sources are check high resistance modules are really a little bit of inefficient

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18. Module Efficiencies top vs bottom top RMS :0.027498 Mean :0.970437 bottom RMS :0.0503772 Mean :0.900905 real data sim data Efficiency / 0.5% normalize top RMS :0.02142 Mean :0.986349 bottom RMS :0.0482003 Mean :0.982505

19. Residual ly0 real data sim data

20. Residual ly1 real datasim data

21. Residual ly2 real datasim data

22. Residual ly3 real data sim data