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Light-nuclei discrimination of the space telescope PAMELA

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.

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Light-nuclei discrimination of the space telescope PAMELA

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  1. 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

  2. Nuclear component in CR: what can we learn?

  3. Secondary/primary ratio

  4. PAMELA TM beam tests at GSI 16/02/2006 --- 20/02/2006 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 mm double view 80 cm TOF : 6 channels ADC and 6 channels TDC, same PAMELA flight electronics with different gain Tracker without magnet

  5. Data sample

  6. Sav (ADC channels) Z2 Saturation limit Sav (ADC channels) Ionization losses discrimination: Tracker silicon layers We took the files obtained by fragmentation of the 1200 MeV/n 12C beam by means of the polyethilene target.

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

  8. C B Be Li He Charge identification

  9. Linearity plot “ADC channel % Z2 “ Charge discrimination (I)

  10. Difference of sums: 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 b.

  11. Courtsey of ISOMAX The Bethe-Bloch reconstruction • Once obtained b for every particle we can plot the energy deposit in one layer vs. b, and fit the different curves of different Z. The fitting functions are superposition of 1/b2 and log(b) behaviour. Charge identification is then obtained by estrapolation from the fitted curves.

  12. Incident 12C He H 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.

  13. Charge discrimination (II) 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.

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

  15. 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.

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