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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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Presentation on theme: "Light-nuclei discrimination of the space telescope PAMELA Roberta Sparvoli for the PAMELA Collaboration University of Rome Tor Vergata and INFN Rome (Italy)"— Presentation transcript:

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 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

4 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

5 Data sample

6 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.

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

8 Charge identification He Li BeB C

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

10 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:

11 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.

12 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

13 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.

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

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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