NIPHAD meeting 16 September 2005, T. Cornelissen 1 Tracking results in the testbeam Thijs Cornelissen

NIPHAD meeting 16 September 2005, T. Cornelissen P 2 Detector setup x y z 3 Pixel layers (6 modules), 4 SCT layers (8 modules), 6 TRT modules. Pixels & SCT inside magnet (B=1.4 T), TRT outside Aluminum plates added between pixel+SCT and SCT+TRT to simulate ATLAS at  = 1.6 TRT SCT Pixel

NIPHAD meeting 16 September 2005, T. Cornelissen P 3 Combined setup

NIPHAD meeting 16 September 2005, T. Cornelissen P 4 Offline tracking algorithms Two offline tracking algorithms available for the testbeam: xKalman and CTBTracking (“Cosmics+Testbeam”). xKalman designed for Atlas, but also works rather well for the testbeam. CTBTracking designed specifically for the testbeam setup. A lightweight algorithm, easily adaptable to the requirements of the different setups used in the testbeam. Written in the new tracking EDM, serves as a testing platform for the new tracking tools Pattern recognition and fitting algorithms are independent, can mix and match with other track finding & fitting algorithms.

NIPHAD meeting 16 September 2005, T. Cornelissen P 5 Four tracks with CTBTracking Run , 180 GeV electrons, B=0 Pixel SCT TRT

NIPHAD meeting 16 September 2005, T. Cornelissen P 6 Ganged pixel ambiguities In this event there were 24 track candidates that passed the standard cuts, CTBTracking has an ambiguity solver that selects the one with the lowest chi2. Simulated track reconstructed track

NIPHAD meeting 16 September 2005, T. Cornelissen P 7 Track fit quality, number of hits Run , 100 GeV pions, B=0 Number of SCT hits χ 2 / DOF Nr of Pixel hits Nr of TRT hits

NIPHAD meeting 16 September 2005, T. Cornelissen P 8 Curved tracks with CTBTracking Run , 20 GeV pions, B=1.4 T

NIPHAD meeting 16 September 2005, T. Cornelissen P 9 Momentum reconstruction Average reconstructed momentum is exactly 9 GeV when only pixel and SCT hits are used. Including the TRT gives a systematic offset of about 0.5 GeV, but the R.M.S. becomes about two times smaller. Clear sign that the TRT is improving the momentum resolution. 9 GeV pions, B=1.4 T Pixel + SCTPixel + SCT + TRT Track momentum

NIPHAD meeting 16 September 2005, T. Cornelissen P 10 Track finding efficiencies DataSimulation 350 GeV  ~100 %96 % 150 GeV  ~100 %97 % 100 GeV  96 %94 % 20 GeV  96 %95 % 9 GeV  97 %95 % 20 GeV e93 % Track finding efficiencies with CTBTracking. Require at least one pixel space-point in the event. Performance with simulation seems slightly worse than with real data (to be understood)

NIPHAD meeting 16 September 2005, T. Cornelissen P 11 Momentum resolution (cont’d) 9 GeV pions simulationdata Pions selected in real data (run ) by requiring <4 TRT HL hits. R.M.S. is about two times bigger in data, and there is an offset of more than 0.5 GeV. Need to work on magnetic field description and alignment. Track momentum

NIPHAD meeting 16 September 2005, T. Cornelissen P 12 Electron brem tails Real data simulation The brem tails are present both in simulation and in real data. The red graph seems to have a longer tail in data than in simulation, suggesting an underestimation of the material in the simulation. Track momentum

NIPHAD meeting 16 September 2005, T. Cornelissen P 13 ID correlations with LAr, muons TrackToCalo C. Bourdarios Offset = 0.31 ± 0.68 Slope = 1.02 ± 0.06 Z (ID) mm Z (MS) mm Muonboy phi (ID) phi (LAr) mm

NIPHAD meeting 16 September 2005, T. Cornelissen P 14 Refitted muon in RecExTB (SL fitter) Run , 180 GeV muons, B=0    / ndof = 136 / 25 The new track fitters were designed to be independent of detector technology, so they can also (re-)fit muon tracks. This is a muonboy track, refitted with the straight line fitter.

NIPHAD meeting 16 September 2005, T. Cornelissen P 15 Combined fit: ID+Muons    / ndof = / 61 (starting from 2*10 9 / 61 )  inner detector Run , 180 GeV muons, B=0

NIPHAD meeting 16 September 2005, T. Cornelissen P 16 Cosmics in SR1 (near pit) TRT SCT Scintillators M. Costa, O. Oye et al.

NIPHAD meeting 16 September 2005, T. Cornelissen P 17 TRT + SCT TRT TRT + SCT residuals With only a few modifications, the CTBTracking algorithm can now successfully reconstruct simulated cosmics. Awaiting real data…

NIPHAD meeting 16 September 2005, T. Cornelissen P 18 Track fitting with multiple scattering Allow the track to change direction at predefined scatter planes, but not ‘for free’:

NIPHAD meeting 16 September 2005, T. Cornelissen P 19 Track parameter resolutions My fit, no m.sc.My fit, w/m. sc.xKalman D0 (mm) Z0 (mm) phi theta q/p 2.4% 2.6% Resolutions on track parameters with 1 GeV muons. Only pixel & SCT hits used. My fit was assuming 2% X0 per pixel layer, 1% X0 per SCT layer.

NIPHAD meeting 16 September 2005, T. Cornelissen P 20 Track parameter pulls d01.5 z01.1 phi1.6 theta1.3 q/p1.3 Track parameter pulls with 1 GeV muons. Including multiple scattering in the fit improves things dramatically, but they are still a bit on the high side. Need to work on material description.

NIPHAD meeting 16 September 2005, T. Cornelissen P 21  2  and  2  probability (1 GeV muons)  w/o multiple scattering  with multiple scattering

NIPHAD meeting 16 September 2005, T. Cornelissen P 22 Outlook CTBTracking has successfully reconstructed millions of events in the testbeam Pattern recognition is done, track fit is steadily improving Would like to repeat combined ID/muon fit, this time with multiple scattering and energy loss included Use energy measurement from the calorimeters?