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Measurement of track length and time-of-flight hypothesis in central ALICE detectors

Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003. Measurement of track length and time-of-flight hypothesis in central ALICE detectors. Sylwester Radomski GSI, Darmstadt Y. Foka, Y. Belikov, K. Safarik S.Radomski@gsi.de Sylwester.Radomski@cern.ch. Sylwester Radomski, GSI

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Measurement of track length and time-of-flight hypothesis in central ALICE detectors

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  1. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Measurement of track length and time-of-flight hypothesis in central ALICE detectors Sylwester Radomski GSI, Darmstadt Y. Foka, Y. Belikov, K. Safarik S.Radomski@gsi.de Sylwester.Radomski@cern.ch

  2. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Introduction Measurement of the time-of-flight is a method of particle type identification. It is used in the momentum range where energy loss do not give sufficient information. • Time-of-flight is measured by TOF detector • Hypothetical time calculated during tracking • length and momentum calculated for the geometry • mass – from particle type hypothesis (each track have 5 h-tof) • Then times are compared and likehood are assigned to hypothesis This work concentrate on measurement of hypothetical time by tracking in ITS, TPC and TRD

  3. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Implementation • Central part implemented in AliKalmanTrack • start time, measure length and time for 5 hypothesis • AddStep called by tracker • TPC & TRD : connect filtered point with predicted point • ITS : connect measured points • linear approximation • TPC -> ITS -> Vertex (start time) -> ITS -> TPC -> TRD • Analysis on the Reference Planes (set of macros written) only tracks with prolongation in all detectors are used

  4. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Simulations • Performance was investigated by simulations • 4 events with GeVSim • pt ~ (1, 2, 3) GeV, eta <-0.9, 0.9> • pt = (0.4 - 3) GeV, eta <-0.9, 0.9> (protons only) • 4 000 particles: e-, e+, pi+, pi-, K+, K- , p, p- • TPC full simulation and reconstruction (Y.B) • TRD full simulation and reconstruction • ITS fast simulation

  5. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Tracking Efficiency TPC in (4544) Fake = 39 e + 484 e - 465 (949) mu+ 491 mu- 485 (976) pi+ 469 pi- 473 (942) K + 362 K - 348 (710) (dacays) p + 497 p - 432 (929) ITS in (3663) Fake = 84 e + 382 e - 374 (756) [0.80] mu+ 389 mu 391 (780) [0.79] pi+ 379 pi- 371 (750) [0.79] K + 294 K - 293 (587) [0.82] p + 371 p - 336 (707) [0.76] TRD in (2910) Fake = 81 e + 307 e - 291 (598) [0.79] mu+ 346 mu- 344 (690) [0.88] pi+ 301 pi- 296 (597) [0.79] K + 216 K - 208 (424) [0.72] (decays) p + 293 p - 227 (520) [0.73]

  6. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Length Resolution RMS = 1.7 mm, 1 mm, 0.7 mm 1 mm – 3 ps

  7. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Time Resolution

  8. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Time Resolution Resolutions:1 GeV 2 GeV 3 GeV electrons 4.8 ps 2.1 ps 1.7 ps pions 5.6 ps 2.1 ps 1.5 ps kaons 28.8 ps 8.9 ps 4.1 ps proton 87.7 ps 28.7 ps 14.8 ps

  9. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Theoretical estimation • Preliminary estimation • for protons resolution limited by momentum resolution • Estimation of error using error-propagation-method • This yield to estimate dependence

  10. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Resolution protons

  11. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Is it enough ? Kaon-Proton Pion-Kaon Proton Kaon Pions

  12. Sylwester Radomski, GSI ALICE Off-line week CERN, March 7, 2003 Summary • Track length and time hypothesis measurement implemented • Full chain (TPC, ITS, TPC, TRD) in operation • Track length measurement precise enough – no correction for helix • Time resolution understood, limited by momentum resolution • Resolution sufficiently good • ALICE NOTE written – close to release

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