Light-nuclei discrimination of the space telescope PAMELA Roberta Sparvoli for the PAMELA Collaboration University of Rome Tor Vergata and INFN Rome (Italy) 20th ECRS – Lisbon (Portugal), 5 – 8 September 2006

Nuclear component in CR: what can we learn?

Secondary/primary ratio ParticleEnergy Anti(p)80 MeV – 190 GeV e+50 MeV – 270 GeV e-50 MeV – 400 GeV p80 MeV – 700 GeV (e-)+(e+)up to 2 TeV Nuclei Z<=8 100 MeV/n – 700 GeV/n Anti(Z)~ 10 -8

PAMELA TM beam tests at GSI 16/02/ /02/ cm TOF : 6 channels ADC and 6 channels TDC, same PAMELA flight electronics with different gain Tracker without magnet TOF system: single paddles of PAMELA TOF S1 : 0.7 cm thick S2 : 0.5 cm thick S3 : 0.7 cm thick TRACKER system: same silicon wafers of PAMELA P1,P2,P3,P4,P5 : 300 m double view

Data sample

Ionization losses discrimination: Tracker silicon layers Z2Z2 Sav (ADC channels) Saturation limit We took the files obtained by fragmentation of the 1200 MeV/n 12 C beam by means of the polyethilene target.

S1 Layer (ADC)S2 Layer (ADC)S3 Layer (ADC) The tracker data are used to clean the data sample ! Ionization losses discrimination: TOF scintillators

Charge identification He Li BeB C

Charge discrimination (I) Z  Linearity plot “ADC channel % Z 2 “

Time-Of-Flight Information If we add the time-of-flight information we increase our capability of particle recognition. K1 and K2 can be derived by the instrument setup and by data collected at known . Difference of sums:

The 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  Courtsey of ISOMAX 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) To fit the curves from GSI test we have taken tha data sample of 12 C 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 He Incident 12 C

Charge discrimination (II) Z  old  new We took the same data sample coming from fragmentation of the 12 C beam at 1200 MeV/n, to compare the two methods. The charge resolution is evidently better, and the abundances results consistent.

Z=1 charge resolution With the sample of data at 45° it is possible to fit also Z=1 peak. Z  10.09

Conclusions 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; Flight data analysis is on-going.