Diapositiva 1

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The PAMELA Experiment Preliminary Results after
Two Years of Data Taking Emiliano Mocchiutti -
INFN Trieste on behalf of the PAMELA Collaboration
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The PAMELA Collaboration
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Overview

• PAMELA physics
• PAMELA apparatus
• Preliminary PAMELA results
• More about PAMELA at ECRS08
• A. N. Kvashnin Measurements of cosmic ray
  particles in the energy range of 1011
  (Wednesday, 1635)
• P. Hofverberg Measurements of low energy
  antiparticles with the PAMELA experiment
  (Wednesday, 1805)
• V. Mikhailov Trapped charged particles
  measurements in radiation belts by PAMELA
  instrument (Thursday, 1220)
• L. Grishanteva Secondary electron and positron
  fluxes in the Earth magnetosphere near the
  geomagnetic equator (Thursday, 1235)
• V. Malvezzi Performance of the PAMELA space
  telescope in the identification of the light
  nuclei cosmic rays component (P5.01)
• L. Marcelli PAMELA mission preliminary results
  about nuclei analysis (P5.02)
• V. Malakhov Methods of reconstruction of pitch
  angle distribution (P2.08)

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PAMELA as a Space Observatory at 1AU
Search for dark matter annihilation Search for
antihelium (primordial antimatter)? Search for
new Matter in the Universe (Strangelets?) Study
of cosmic-ray propagation Study of solar physics
and solar modulation Study of terrestrial
magnetosphere Study of high energy electron
spectrum (local sources?)
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PAMELA apparatus
_

• Time-Of-Flight (ToF)
• plastic scintillators PMT
• Trigger
• Albedo rejection
• - Charge identification from dE/dX.
• Anti-Coincidence
• plastic scintillators PMT
• - rejection of particles out of acceptance
• Electromagnetic calorimeter
• W/Si sampling (16.3 X0, 0.6 ?I)
• Discrimination e / p, anti-p / e-
• (shower topology)
• Direct E measurement for e-
• Neutron detector
• He3 counters polyetilene
• High-energy e/h discrimination

GF 21.5 cm2 sr Mass 470 kg Size
130x70x70 cm3 Power Budget 360W

• Spectrometer
• microstrip silicon tracking system
  permanent magnet
• Magnetic rigidity ? R pc/Ze
• Charge sign
• Charge value from dE/dx

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Design Performance

• energy range
• Antiprotons 80 MeV - 190 GeV
  
• Positrons 50 MeV 270 GeV
  
• Electrons up to 400 GeV
• Protons up to 700 GeV
• Electronspositrons up to 2 TeV (from
  calorimeter)
• Light Nuclei up to 200 GeV/n
  He/Be/C
• AntiNuclei search sensitivity of
  3x10-8 in He/He

• Simultaneous measurement of many cosmic-ray
  species
• New energy range
• Unprecedented statistics

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Resurs-DK1 Satellite

• Main task multi-spectral remote sensing of
  earths surface
• Built by TsSKB Progress in Samara, Russia
• Lifetime gt3 years
• Data transmitted to ground via high-speed radio
  downlink
• PAMELA mounted inside a pressurized container

Mass 6.7 tonnes Height 7.4 m Solar array area
36 m2
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Resurs-DK1 Launch15th June 200616 Gigabytes
trasmitted daily to Ground Station(NTsOMZ) in
MoscowTill now PAMELA has collected 11 TB
of data, corresponding to gt109 triggers
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PAMELA Orbit

• Low-earth elliptical orbit
• 350 610 km
• Quasi-polar (70o inclination)

Low energy particles stops inside the apparatus ?
Counting rates S1gtS2gtS3
Outer radiation belt
Download _at_orbit 3754 15/02/2007 073500 MWT
S1 S2 S3
Inner radiation belt (SAA)
Ratemeters Independent from trigger
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Proton and Helium spectra
Preliminary
Very high statistics over a wide energy range ?
Precise measurement of spectral shape ?
Possibility to study time variations and
transient phenomena
A. N. Kvashnin (Wednesday, 1635)
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Proton spectra and solar modulation
Increasing GCR flux
July 2006 August 2007 February 2008
Decreasing solar activity
Preliminary
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Primary and Albedo (sub-cutoff) measurements
Preliminary
Geomagnetic cutoff (GV/c)
0.4 to 0.5
1.0 to 1.5
Secondary reentrant-albedo protons
1.5 to 2.0
2 to 4
4 to 7
7 to 10
10 to 14

• Up-ward going albedo excluded
• SAA excluded

Magnetic equator
gt 14
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Trapped proton flux in the Inner Van Allen Belt
(Shout Atlantic Anomaly)
Black B gt 0.3 GRed 0.22 G lt B lt 0.23 GBlue
0.21 G lt B lt 0.22 GGreen 0.20 G lt B lt 0.21
GPink 0.19 G lt B lt 0.20 GTurquoise 0.19 G gt
B
V. Mikhailov (Thursday, 1220) L. Grishanteva
(Thursday, 1235)
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December 13th 2006 event
SEPs
Solar quiet spectrum
Preliminary!
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Preliminary Results B/C
Preliminary
V. Malvezzi (P5.01) L. Marcelli (P5.02)
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PAMELA anti-protons

• More than 107 p and 1000 p have been identified
  between 1 and 100 GeV
• 300 p over 10 GeV

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Anti-proton to proton ratio PAMELA
Preliminary
P. Hofverberg (Wednesday, 1805)
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Anti-proton to proton ratio
Preliminary
P. Hofverberg (Wednesday, 1805)
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PAMELA positrons

• Till March 2nd 2008 2x105 e- and 2x104 e from
  200 MeV up to 10 GeV have been identified
• About 15000 positrons over 1 GeV

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Positron p background suppression
e-
Preliminary
p (non-int)
e
p (int)
Fraction of charge released along the calorimeter
track (left, hit, right)
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Positron p background suppression
Preliminary
e-
p
e

Fraction of charge released along the calorimeter
track (left, hit, right)
Energy-momentum match
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Positron p background suppression
Preliminary
e-
e
p

Energy-momentum match Starting point of shower
Longitudinal profile
Fraction of charge released along the calorimeter
track (left, hit, right)
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Positron p background evaluation
e-
Preliminary
p
e
pre- sampler p

Energy-momentum match Starting point of shower
Fraction of charge released along the calorimeter
track (left, hit, right)
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Positron fraction
Preliminary
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Conclusions

• PAMELA has been in orbit and studying cosmic rays
  for 25
• months. gt109 triggers registered, and 11 TB of
  data has been
• down-linked.
• Antiproton to proton flux ratio (100 MeV - 100
  GeV) shows no
• significant deviations from secondary
  expectations. More high
• energy data to come (up to 150 GeV).
• Positron fraction (400 MeV - 10 GeV) indicates
  charge
• dependent modulation effects. More data to come
  at lower and
• higher energies (up to 200 GeV).
• PAMELA is studying elemental spectra up to Z8,
  and low mass
• isotopes.
• PAMELA also measures the high energy tail of
  solar particle events.
• http//pamela.roma2.infn.it