1. Measurements of Cosmic-Ray Helium, Lithium and Beryllium Isotopes with the PAMELA- Experiment Wolfgang Menn University of Siegen On behalf of the PAMELA collaboration ICRC 2011 Beijing - 15 August 2011

2. PAMELA Search for AntimatterSearch for Antimatter Search for Dark MatterSearch for Dark Matter Study of Cosmic Ray Propagation (e. g. Isotopes)Study of Cosmic Ray Propagation (e. g. Isotopes) Study Solar PhysicsStudy Solar Physics Study Solar ModulationStudy Solar Modulation Measurements in the Earth Magnetic EnvironmentMeasurements in the Earth Magnetic Environment Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics

3. Isotope Measurements with the Velocity versus Rigidity Technique Velocity versus Rigidity Technique Velocity versus Rigidity Technique: Rigidity from magnetic spectrometer Beta from ToF, Cherenkov, dEdx… Mass Resolution: β-Measurement Spectrometer Isotope Experiments (ISOMAX etc.): 3σ < Δm mass resolution ~ 0.3 amu

4. Spectrometer: Measures Rigidity R: R=p / Z∙e Permanent magnet: magnetic field ~ 0.45 T Si-microstrip tracking system: 6 layers of silicon microstrip detectors 3 µm resolution in bending view → MDR ~ 1 TV PAMELA Instrument: Spectrometer 45 cm

5. PAMELA Spectrometer 6 layers @ 3 µm, 0.45 T, 0.45 m height→ MDR ~1000 GV CERN Beam Test Proton Data (dR/R) mult ~ (x/X 0 )/(beta · B·dL) Silicon Tracker doesn`t need support structure → minimal multiple scattering ~3.5 % Isotope Measurements

6. Time-Of-Flight (TOF): plastic scintillators + PMT time resolution ~300 ps for Z=1, ~100ps for Z ≥ 2 PAMELA Instrument: Time-of-Flight 78 cm

7. Velocity versus Rigidity Technique Velocity versus Rigidity Technique 4 He PAMELA Tof + Spectrometer Expected Mass Resolution for 4 He 125 400 800 1200 E kin (MeV/nuc)

8. PAMELA:Helium Isotopes with ToF He 4 He 3 He 4

9. PAMELA:Helium Isotopes with ToF Data 125 400 800 1200 E kin (MeV/nuc)

10. Measurements of Helium Isotopes PAMELA ToF preliminary OG1.1 842: „Measurement of Deuterium and 3He component in cosmic rays with Pamela experiment“

11. Electromagnetic W/Si calorimeter 44 Si layers (X/Y) +22 W planes 380 µm thick silicon strips, 4224 channels 16.3 X 0, 0.6 λ I Dynamic range ~1100 mip PAMELA Instrument: Calorimeter

12. PAMELA Calorimeter Select non-interacting events For example: 2.98 GV Lithium Energy loss in each silicon layer of the calorimeter: non-interacting events: ~ 70-80% loss in statistics Expected energy-loss calculated with Bethe-Bloch equation

13. Cut away highest 50% Use the lower 50% (black points) to calculate a mean dEdx “Truncated Mean” Method Helium He 4 He 3

14. Spectrometer + ToF Spectrometer + Calorimeter dEdxComparison He 4 He 3 He 4

15. Chi² - Method Example:Helium 3.0 GV:Bethe-Bloch calculation Compare data points with theoretical prediction Best Chi² wins! Plot Chi² vs. Mass

16. Chi² - Method No good minimum for Chi² He 4 He 3

17. Comparison ToF & Calorimeter (Chi²-Method) Helium 2.5 – 2.7 GV ToF: 0.42 amu Calorimeter (Chi²): 0.25 amu

18. Mass resolution with “Bethe-Bloch-Chi²” Method Helium ToF Calorimeter (Chi²-Method) Different methods still under test, work in progress… 125 400 800 1200 E kin (MeV/nuc)

19. Measurements of Helium Isotopes PAMELA ToF preliminary PAMELA Calorimeter OG1.1 842: „Measurement of Deuterium and 3He component in cosmic rays with Pamela experiment“

20. “Truncated Mean” Method: Lithium

21. GEANT4 simulation of Calorimeter: IOFFE Institute St. Petersburg E.A. Bogomolov, G.I. Vasilyev, S.Yu. Krut’kov Example: Li 2.9 – 3.1 GV

22. “Truncated Mean” Method: Lithium 3.3 – 3.5 GV

23. Measurements of Lithium Isotopes preliminary

24. “Truncated Mean” Method: Beryllium

25. 2.9 – 3.1 GV “Truncated Mean” Method: Beryllium

26. 3.3 – 3.5 GV “Truncated Mean” Method: Beryllium

27. GEANT4 simulation for Beryllium shows room for improvement: Do NOT use all layers?

28. Measurements of Beryllium Isotopes PAMELA pre-preliminary preliminary

29. Summary Momentum resolution of PAMELA spectrometer ca. 3.5 % ToF analysis underway, shows expected mass resolution Analysis using multiple dEdx with calorimeter in progress Helium results show improved mass resolution compared to ToF GEANT4 simulation is used for comparison with data First results show that PAMELA will be able to provide new data for Lithium and Beryllium isotopes up to ~ 1 – 1.5 GeV/n Work in Progress …. Thank You !