A.A.Petrukhin National Research Nuclear University MEPhI, Moscow, Russia
The method of the low-energy antiproton identification by stopping in the coordinate- sensitive...
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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
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Transcript of The method of the low-energy antiproton identification by stopping in the coordinate- sensitive...
The method of the low-energy antiproton identification by stopping in the coordinate-
sensitive PAMELA calorimeter
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Svetlana Rodenko (MEPhI) Moscow
International conference on particle physics and astrophysics National Research Nuclear University MEPhI
5-10 October 2015
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An interaction between p and the calorimeter matter
By deflection in the magnetic field;
By searching for an annihilation in the calorimeter matter;
The identification of antiprotons:
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Electromagnetic calorimeter
The imaging calorimeter is used for separation of electrons and positrons from antiproton and proton.
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Simulation
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.
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The antiproton identification algorithm
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)
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Searching for the point of entry into the calorimeter
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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
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The energy release distribution
Energy release, mipEnergy release, mip
Energy release, mip Energy release, mip
Even
t
Even
tEven
t
Event
p (1 GeV)
p (2.5 GeV) p (5 GeV)
_p (0.75 GeV)
the point of entry the point of entry
the point of entry the point of entry
the point of annihilation
the point of annihilation
the point of annihilation
the point of annihilation
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Energy release, mip
Energy release, mipEnergy release, mip
Energy release, mip
Event
Event
Event
Event
p (1 GeV)
p (2.5 GeV) p (5 GeV)
p (0.75 GeV)_
The total energy release distribution
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Analysis of topology of annihilation (tracks of secondary particles)
Θ, deg
Sti
p n
on z
ero
energ
y r
ele
ase
,
mip
Θ 1 Θ 2 Θ 3 Θ4
Θ
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Triggered strips dependence on angle Θ mean
Antiprotons (0,75GeV)
Protons (5 GeV)
Θ mean, deg
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Example of selected antiproton from MC
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Example of selected antiproton from MC
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Example of selected proton from MC
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The effectiveness of the selection and backgroundParticle Energy, GeV Selected Total amount
of eventsEfficiency /rejection
Antiprotons 0,75 2573 10 000 0,25
Protons
0,75 0 46 031 0
1 0 46 256 0
1,25 0 46 166 0
1,75 2 46 166 4,3e-5
2 9 46 119 1,9e-4
2,5 9 46 440 1,9e-4
3 29 46 223 6,3e-4
4 57 46 251 1,2e-3
5 77 46 048 1,7e-3
10 147 41 929 3,5e-3
15 174 41 825 4,2e-3
π-mesons:1 3 46 160 6,5e-5
1,25 7 41 825 1,7e-4
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Conclusion
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
