1. The method of the low-energy antiproton identification by stopping in the coordinate- sensitive PAMELA calorimeter 1 Svetlana Rodenko (MEPhI) Moscow International conference on particle physics and astrophysics National Research Nuclear University MEPhI 5-10 October 2015

2. An interaction between p and the calorimeter matter 2 By deflection in the magnetic field; By searching for an annihilation in the calorimeter matter; The identification of antiprotons:

3. Electromagnetic calorimeter 3 The imaging calorimeter is used for separation of electrons and positrons from antiproton and proton.

4. Simulation 4  Antiprotons: 0.75 GeV in the aperture of PAMELA.  Protons: 0.35 ‒ 0.95, 1, 1.1, 1.5, 2, 2.5, 3, 4, 5, 7.5, 10, 12.5, 15 GeV.  π -mesons: 0.75, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5, 7.5, 10, 12.5, 15 GeV.  We want to identify an antiprotons on a background of protons and π -mesons.

5. The antiproton identification algorithm 5  Search for the point of entry of particle into the calorimeter and calculation  Search for the point of annihilation and calculation  Analysis of topology of annihilation (tracks of secondary particles)

6. Searching for the point of entry into the calorimeter 6

7. 7 Searching for point of annihilation  Select the first few points with maximum energy release  Connect them with the point of entry  Calculate an energy release in cylinder around this direction ± 1 strip  Select cylinder with the maximum energy release

8. The energy release distribution 8 Energy release, mip Event p (1 GeV) p (2.5 GeV) p (5 GeV) _ p (0.75 GeV) the point of entry the point of annihilation

9. 9 Energy release, mip Event p (1 GeV) p (2.5 GeV) p (5 GeV) p (0.75 GeV) _ The total energy release distribution

10. 10 Analysis of topology of annihilation (tracks of secondary particles) Θ, deg Stip non zero energy release, mip Θ 1Θ 1 Θ 2Θ 2 Θ 3Θ 3 Θ4Θ4 Θ

11. Triggered strips dependence on angle Θ mean 11 Antiprotons (0,75GeV) Protons (5 GeV) Θ mean, deg

12. Example of selected antiproton from MC 12

13. 13 Example of selected antiproton from MC

14. 14 Example of selected proton from MC

15. The effectiveness of the selection and background 15 ParticleEnergy, GeVSelectedTotal amount of events Efficiency /rejection Antiprotons0,75257310 0000,25 Protons 0,75046 0310 1046 2560 1,25046 1660 1,75246 1664,3e-5 2946 1191,9e-4 2,5946 4401,9e-4 32946 2236,3e-4 45746 2511,2e-3 57746 0481,7e-3 1014741 9293,5e-3 1517441 8254,2e-3 π -mesons: 1346 1606,5e-5 1,25741 8251,7e-4

16. Conclusion 16  AC and TOF may be used for protons and high energy π - mesons rejection.  High energy protons have a speed close to 1 ( β ~ 1), antiprotons are slow, therefore it is possible to build a velocity distribution measured by the TOF and cut off protons.  Apply a method to experimental data