Light-nuclei Light-nuclei discrimination discrimination of the space of the space telescope PAMELA telescope PAMELA Roberta Sparvoli Roberta Sparvoli for the PAMELA Collaboration for the PAMELA Collaboration University of Rome Tor Vergata and INFN University of Rome Tor Vergata and INFN Rome (Italy) Rome (Italy) 20th ECRS – Lisbon (Portugal), 5 – 8 September 2006
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Light-nuclei discrimination of the space telescope PAMELA Roberta Sparvoli for the PAMELA Collaboration University of Rome Tor Vergata and INFN Rome (Italy)
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Time-Of-Flight InformationTime-Of-Flight InformationIf we add the time-of-flight information we increase our capability of particle recognition.
K1 and K2 can be derived by the instrumentsetup and by data collected at known .
Difference of sums:
The Bethe-Bloch reconstructionThe Bethe-Bloch reconstruction
Once obtained for every particle we can plot the energy deposit in one layer vs. and fit the different curves of different Z
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sey o
f IS
OM
AX
The fitting functions are superposition of 1/2 and log() behaviour.
Charge identification is then obtained by estrapolation from the fitted curves.
Fitting of curves f(Z)Fitting of curves f(Z)
To fit the curves from GSI test we have taken tha data sample of 12C at 200 MeV/n with poly target, recorded at an angle of 45°. In this way many slow protons at high deposit are triggered, and we can fit both Z=1 and Z=2 curves.
H
HeIncident 12C
Charge discrimination (II)Charge discrimination (II)
Z old new
2 0.27 0.14
3 0.29 0.09
4 0.19 0.11
5 0.13 0.09
6 0.12 0.04
We took the same data sample coming from fragmentation of the 12C beam at 1200 MeV/n, to compare the two methods. The charge resolution is evidently better, and the abundances results consistent.
Z=1 charge resolutionZ=1 charge resolutionWith the sample of data at 45° it is possible to fit also Z=1 peak.
Z 1 0.09
ConclusionsConclusions• Data collected at a beam test show the good
capabilities of PAMELA at recognizing light nuclei;
• Both information from energy loss alone and “energy loss + TOF” are used for charge recongition; in the second case the results are excellent;
• Parallel analysis from different detectors (TOF, tracker, calorimeter) can additionally improve the in-flight resolution;
• In addition, also isotope reconstruction will be perfomed in-flight, thank to the measurement of the particle rigidity;