Light-nuclei Light-nuclei discrimination discrimination

of the space of the space telescope telescope PAMELAPAMELA

Roberta SparvoliRoberta Sparvolifor the PAMELA Collaborationfor the PAMELA Collaboration

University of Rome Tor Vergata and INFNUniversity of Rome Tor Vergata and INFNRome (Italy)Rome (Italy)

20th ECRS – Lisbon (Portugal), 5 – 8 September 2006

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

Secondary/primary ratioSecondary/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

NucleiZ<=8

100 MeV/n – 700 GeV/n

Anti(Z) ~ 10-8

PAMELA TM beam tests at GSI PAMELA TM beam tests at GSI 16/02/2006 --- 20/02/200616/02/2006 --- 20/02/2006

80 cm

TOF : 6 channels ADC and 6 channels TDC, same PAMELA flight electronics with different gainTracker without magnet

TOF system: single paddles of PAMELA TOF

S1 : 0.7 cm thickS2 : 0.5 cm thickS3 : 0.7 cm thick

TRACKER system: same silicon wafers of PAMELA

P1,P2,P3,P4,P5 :300 m double view

Data sampleData sample

Ionization losses discrimination: Ionization losses discrimination: Tracker silicon layersTracker silicon layers

Z2Sav (

AD

C c

hannels

)

Sav (ADC channels) Saturation limit

We took the files obtained by fragmentation of the 1200 MeV/n 12C 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: Ionization losses discrimination: TOF scintillatorsTOF scintillators

Charge identificationCharge identification

He

Li

Be

B

C

Charge discrimination (I)Charge discrimination (I)

Z 2 0.27

3 0.29

4 0.19

5 0.13

6 0.12

Linearity plot “ADC channel % Z2 “

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

Court

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;

• Flight data analysis is on-going.