Light-nuclei discrimination of the space telescope PAMELA

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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)

20th ECRS Lisbon (Portugal), 5 8 September
2006
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Nuclear component in CR what can we learn?
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Secondary/primary ratio
Particle Energy
Anti(p) 80 MeV 190 GeV
e 50 MeV 270 GeV
e- 50 MeV 400 GeV
p 80 MeV 700 GeV
(e-)(e) up to 2 TeV
Nuclei Zlt8 100 MeV/n 700 GeV/n
Anti(Z) 10-8
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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
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Data sample
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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.
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Ionization losses discrimination TOF
scintillators
The tracker data are used to clean the data
sample !
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Charge identification
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Charge discrimination (I)
Z s
2 0.27
3 0.29
4 0.19
5 0.13
6 0.12
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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.
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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.
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Fitting of curves f(Z)
To fit the curves from GSI test we have taken tha
data sample of 12C at 200 GeV/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 Z1 and Z2 curves.
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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.
Z sold snew
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
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Z1 charge resolution

• With the sample of data at 45 it is possible to
  fit also Z1 peak.

Z s
1 0.09
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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.