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

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Moscow St. Petersburg Russia: Sweden: KTH, Stockholm Germany: Siegen Italy: BariFlorenceFrascatiTriesteNaplesRome CNR, Florence The PAMELA Collaboration

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 ” (Wednesday, 16:35)  P. Hofverberg “Measurements of low energy antiparticles with the PAMELA experiment” (Wednesday, 18:05)  V. Mikhailov “Trapped charged particles measurements in radiation belts by PAMELA instrument” (Thursday, 12:20)  L. Grishanteva “Secondary electron and positron fluxes in the Earth magnetosphere near the geomagnetic equator” (Thursday, 12:35)  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)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 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?)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 PAMELA apparatus GF: 21.5 cm 2 sr Mass: 470 kg Size: 130x70x70 cm 3 Power Budget: 360W Spectrometer microstrip silicon tracking system + permanent magnet - Magnetic rigidity  R = pc/Ze - Charge sign - Charge value from dE/dx 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 λI) - Discrimination e+ / p, anti-p / e - (shower topology) - Direct E measurement for e - Neutron detector He 3 counters + polyetilene: - High-energy e/h discrimination + _

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 energy range  Antiprotons 80 MeV GeV  Positrons 50 MeV – 270 GeV  Electrons up to 400 GeV  Protons up to 700 GeV  Electrons+positrons 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 Design Performance

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Mass: 6.7 tonnes Height: 7.4 m Solar array area: 36 m 2  Main task: multi-spectral remote sensing of earth’s surface  Built by TsSKB Progress in Samara, Russia  Lifetime >3 years  Data transmitted to ground via high-speed radio downlink  PAMELA mounted inside a pressurized container Resurs-DK1 Satellite

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Resurs-DK1 Launch 15 th June Gigabytes trasmitted daily to Ground Station (NTsOMZ) in Moscow Till ~now PAMELA has collected ~11 TB of data, corresponding to >10 9 triggers

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Low-earth elliptical orbit 350 – 610 km Quasi-polar (70 o inclination) PAMELA Orbit 3754 – 15/02/ :35:00 MWT S1 S2 S3 orbit 3752 orbit 3753 orbit 3751 Inner radiation belt (SAA) Outer radiation belt NP SP EQ EQ 95 min S1 S2 S3 Low energy particles stops inside the apparatus  Counting rates: S1>S2>S3 SAA Ratemeters Independent from trigger

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Preliminary Proton and Helium spectra 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, 16:35)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Proton spectra and solar modulation Interstellar spectrum July 2006 August 2007 February 2008 Decreasing solar activity Increasing GCR flux Preliminary

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Preliminary Primary and Albedo (sub-cutoff) measurements 0.4 to to to to 4 > to 14 7 to 10 4 to 7 Geomagnetic cutoff (GV/c) Secondary reentrant-albedo protons Magnetic equator Up-ward going albedo excluded SAA excluded

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Black B > 0.3 G Red 0.22 G B P/(cm^2 sr GeV s) Trapped Galactic Trapped proton flux in the Inner Van Allen Belt (Shout Atlantic Anomaly) V. Mikhailov (Thursday, 12:20) L. Grishanteva (Thursday, 12:35)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Preliminary! December 13 th 2006 event Solar quiet spectrum SEPs

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Preliminary Preliminary Results B/C V. Malvezzi (P5.01) L. Marcelli (P5.02)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008  More than 10 7 p and ~1000 p have been identified between 1 and 100 GeV  ~300 p over 10 GeV PAMELA anti-protons

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Anti-proton to proton ratio: PAMELA Preliminary P. Hofverberg (Wednesday, 18:05)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Anti-proton to proton ratio Preliminary P. Hofverberg (Wednesday, 18:05)

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008  Till March 2 nd 2008 ~2x10 5 e - and ~ 2x10 4 e + from 200 MeV up to 10 GeV have been identified  About positrons over 1 GeV PAMELA positrons

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Preliminary p (non-int) e-e-e-e- e+e+e+e+ Fraction of charge released along the calorimeter track (left, hit, right) p (int) Positron: p background suppression

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 e-e-e-e- Fraction of charge released along the calorimeter track (left, hit, right) p e+e+e+e+ + Energy-momentum match Preliminary Positron: p background suppression

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 e-e-e-e- Fraction of charge released along the calorimeter track (left, hit, right) p e+e+e+e+ + Energy-momentum match Starting point of shower Longitudinal profile Preliminary Positron: p background suppression

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 e-e-e-e- Fraction of charge released along the calorimeter track (left, hit, right) p e+e+e+e+ + Energy-momentum match Starting point of shower Preliminary Positron: p background evaluation “pre- sampler” p

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008 Positron fraction: Preliminary

Emiliano Mocchiutti - INFN Trieste - 21 st European Cosmic Ray Symposium, Košice 10 th September 2008  PAMELA has been in orbit and studying cosmic rays for ~25 months. >10 9 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 Z=8, and low mass isotopes.  PAMELA also measures the high energy tail of solar particle events. Conclusions