1. Measurement of track length and time-of-flight hypothesis
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

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. Implementation Central part implemented in AliKalmanTrack
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. Simulations Performance was investigated by simulations
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 = ( ) 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. Tracking Efficiency Sylwester Radomski, GSI ALICE Off-line week
CERN, March 7, 2003
Tracking Efficiency
TPC in (4544) Fake = 39
e e (949)
mu mu (976)
pi pi (942)
K K (710) (dacays)
p p (929)
ITS in (3663) Fake = 84
e e (756) [0.80]
mu mu (780) [0.79]
pi pi (750) [0.79]
K K (587) [0.82]
p p (707) [0.76]
TRD in (2910) Fake = 81
e e (598) [0.79]
mu mu (690) [0.88]
pi pi (597) [0.79]
K K (424) [0.72] (decays)
p p (520) [0.73]

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

8. Time Resolution Resolutions: 1 GeV 2 GeV 3 GeV
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 ps 1.5 ps
kaons ps 8.9 ps 4.1 ps
proton ps ps ps

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

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

12. Summary Track length and time hypothesis measurement implemented
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