1. Nicolo’ Masi, Andrea Tiseni TOF Group Bologna
22/03/12
Rate of Protons and Antiprotons
Nicolo’ Masi, Andrea Tiseni TOF Group Bologna
N. Masi, A. Tiseni, Rate of Protons and Antiprotons Apr 2012

2. Summary Dark Matter Antiproton Searches:
22/03/12
Dark Matter Antiproton Searches:
Selection of Protons and Antiprotons and live time
Rate of Protons and Antiprotons with TRD+ECAL+FULL TRACKER
Rate of Protons and Antiprotons with TRD+FULL TRACKER
AntiProton to Proton Ratio
Steps:
MonteCarlo Efficiencies studies
Fluxes Analysis and acceptance
Unfolding procedure
Goals:
We’re reconstructing the Protons and Antiprotons spectra, using different methods (TRD+ECAL+full tracker, TRD + full tracker).
By now, we have analyzed the rates for all B550 pass 2 AMS Data = rootfiles

3. Selection of Proton and Electrons:
22/03/12
Selection of protons and Electrons with a program developed by ECAL and TRD group with the contribution of TOF and Tracker people.
Preselection:
Downgoing particle with: 0.6< β < 1.2
South Atlantic and Pole Exclusion
Z=1 ± 0.3
TOF, TRD, Tracker, ECAL common cuts (only in TRD+ECAL+full tracker method)
N. Masi, A. Tiseni, Rate of Protons and Antiprotons Apr 2012

4. Proton and Electron Selection
22/03/12
Proton:
Likelihood Electron/Proton > 0.8
Likelihood Helium/Proton > 1.9
EBDT < -0.8
Cut on the ratio Energy Reconstructed over Rigidity: EnergyE/Rigidity < 0.1
Momentum > 0
Antiproton:
Likelihood Electron/Proton > 0.8
Likelihood Helium/Electron > 1.9
EBDT < -0.8
Cut on the ratio Energy Reconstructed over Rigidity:
EnergyE/Rigidity < 0.1
Momentum < 0
N.B: EBDT is used only in TRD+ECAL+Full Tracker METHOD
N. Masi, A. Tiseni, Rate of Protons and Antiprotons Apr 2012

5. Livetime
22/03/12

6. Proton Rate (TRD+ECAL+Full Tracker Method)
22/03/12
Protons/(sec*GeV)

7. Proton Rate (TRD+Full Tracker Method)
22/03/12
Protons/(sec*GeV)

8. AntiProton Rate (TRD+Full Tracker Method)
22/03/12
AntiProtons/(sec*GeV)

9. AntiProton Rate (TRD+ECAL+Full Tracker Method)
22/03/12
AntiProtons/(sec*GeV)

10. No operative Likelihood & spillover
AntiProton Fraction
22/03/12
No operative Likelihood & spillover
Correct PAMELA Ratio

11. MC Preliminary Efficiency
From few antiprotons rootfiles B550 v5 in the low energy range
(T < 10 GeV) :
total events analyzed:
clean events: (3.1% of total)
Clean Events = Minimum BIAS = Trigger && TrkRigAsim Cut && Beta && Track matches
SAA: No effect on MC
trd golden: (2.3% of total, 73% of clean events)
ecal golden: (2.5% of total, 79% of clean events)
golden di cuts: (1.8% of total, 58% of clean events)
total: p 2
total: antip (1.8% of total, 58% of clean events)
TRD & ECAL selectors (Likelihood and EBDT) : zero statistics

12. Fluxes Data: No Brand News in these 90 days of 2012
From PAMELA and FERMI
electron
Electron + positron

13. Fluxes Data: No Brand News in these 90 days of 2012
Positron fraction

14. Fluxes Data: No Brand News in these 90 days of 2012
proton
helium

15. Fluxes Data: No Brand News in these 90 days of 2012
Antiproton/proton
Antiproton

16. Fluxes Analysis
Without acceptance factor : 0.03 , for TRD+Full Tracker
and TRD+ECAL+Full Tracker
Without ECAL, without acceptance factor

17. Higher than antiprotons one
Number of particle measured by AMS with a 10^-2 acceptance & efficiency factor in 1 year
10000
100
10^-2 ÷ 1 10 1
100
Higher than antiprotons one 10
positrons 10

18. Unfolding
Flat Multidimennsional Step Function Plus Exponential Smoothing
Multinomial or Poissonian Functions

19. If we define the efficiency:
we can compute the true spectrum with the unfolded data for each bin:
Data
Posterior/Inverse probability calculated with previous Bayes Theorem
Smearing/migration effect

20. Conclusions
22/03/12
Background Studies:
contamination of electrons for antiproton signal, especially for the HE range (T > 100 GeV);
eventual contamination of positrons in proton signal at High Energy;
contamination of protons and positrons in antiproton signal for all energies.
Unfolding software to produce the true spectra