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First results from PAMELA space experiment

First results from PAMELA space experiment. Oscar Adriani University of Florence INFN – Florence, Italy On behalf of the PAMELA collaboration. Italy :. CNR, Florence. Bari. Florence. Frascati. Naples. Rome. Trieste. Russia :. Moscow St. Petersburg. Germany :. Sweden :. Siegen.

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First results from PAMELA space experiment

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  1. First results from PAMELA space experiment Oscar Adriani University of Florence INFN – Florence, Italy On behalf of the PAMELA collaboration

  2. Italy: CNR, Florence Bari Florence Frascati Naples Rome Trieste Russia: Moscow St. Petersburg Germany: Sweden: Siegen KTH, Stockholm Tha PAMELA collaboration Oscar Adriani ISVHECRI 2008

  3. Pamela’s scientific objectives • Study antiparticles in cosmic rays • Search for antimatter • Search for dark matter (e+ and pbar spectra) • Study cosmic-ray propagation • Study solar physics and solar modulation • Study the electron spectrum (local sources?) Anti-nucleosyntesis Evaporation of primordial black holes WIMP dark-matter annihilation in the galactic halo Background: CR interaction with ISM CR + ISM  p-bar + … Oscar Adriani ISVHECRI 2008

  4. PAMELA nominal capabilities Energy range • Antiprotons 80 MeV - 150 GeV • Positrons50 MeV – 270 GeV • Electronsup to 400 GeV • Protons up to 700 GeV • Electrons+positronsup to 2 TeV (from calorimeter) • Light Nuclei up to 200 GeV/n He/Be/C • AntiNuclei search • Simultaneous measurement of many cosmic-ray species • New energy range • Unprecedented statistics Oscar Adriani ISVHECRI 2008

  5. PAMELA detectors Main requirements  high-sensitivity antiparticle identification and precise momentum measurement + - • Time-Of-Flight • plastic scintillators + PMT: • Trigger • Albedo rejection; • Mass identification up to 1 GeV; • - Charge identification from dE/dX. • 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 • plastic scintillators + PMT: • 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 • It provides: • - Magnetic rigidity R = pc/Ze • Charge sign • Charge value from dE/dx Oscar Adriani ISVHECRI 2008

  6. PAMELA milestones Mirko Boezio, INFN Trieste - ICHEP08, 2008/08/01 Oscar Adriani ISVHECRI 2008 Launch from Baikonur: June 15th 2006, 0800 UTC. Power On: June 21st 2006, 0300 UTC. Detectors operated as expected after launch PAMELA in continuous data-taking mode since commissioning phase ended on July 11th 2006 As of ~ now: • ~600 days of data taking (~73% live-time) • ~10 TByte of raw data downlinked • >109 triggers recorded and under analysis

  7. 32.3 GV positron Oscar Adriani ISVHECRI 2008

  8. 36 GeV/c interacting proton Oscar Adriani ISVHECRI 2008

  9. Galactic H and He spectra Preliminary!! Very high statistics over a wide energy range  Precise measurement of spectral shape  Possibility to study time variations and transient phenomena Power-law fit: ~ E-g g~ 2.76 for Z=1 g ~ 2.71 for Z=2 (statistical errors only) Oscar Adriani ISVHECRI 2008

  10. Geomagnetic cutoff (GV/c) 0.4 to 0.5 1.0 to 1.5 1.5 to 2.0 2 to 4 4 to 7 7 to 10 10 to 14 > 14 Geomagnetic cutoff Preliminary!! (statistical errors only) Magnetic poles ( galactic protons) Secondary reentrant-albedo protons Magnetic equator • Up-ward going albedo excluded • SAA excluded Oscar Adriani ISVHECRI 2008

  11. Interstellar spectrum PAMELA Ground neutron monitor sun-spot number Solar modulation Preliminary!! (statistical errors only) Increasing GCR flux July 2006 August 2007 February 2008 Decreasing solar activity Oscar Adriani ISVHECRI 2008

  12. Preliminary Results B/C Preliminary Calorimeter based charge identification! Oscar Adriani ISVHECRI 2008

  13. Antiprotons Oscar Adriani ISVHECRI 2008

  14. High-energy antiproton analysis Event selected from 590 days of data Basic requirements: • Clean pattern inside the apparatus • single track inside TRK • no multiple hits in S1+S2 • no activity in CARD+CAT • Minimal track requirements • energy-dependent cut on track c2 (~95% efficiency) • consistency among TRK, TOF and CAL spatial information • Galactic particle • measured rigidity above geomagnetic cutoff • Down-ward going particle (no albedo) S1 CARD CAT S2 . TOF TRK CAS S3 CAL S4 ND Oscar Adriani ISVHECRI 2008

  15. Calorimeter Selection e- Energy measured in Calo/ Deflection in Tracker (MIP/GV) e+ ‘Electrons’ p, d p ‘Hadrons’ Tracker Identification Protons (& spillover) Antiprotons Strong track requirements: MDR > 850 GV Minimal track requirements Oscar Adriani ISVHECRI 2008

  16. Antiproton/Proton ratio Preliminary Oscar Adriani ISVHECRI 2008

  17. Antiproton/Proton Ratio Preliminary Oscar Adriani ISVHECRI 2008

  18. Positrons Oscar Adriani ISVHECRI 2008

  19. Positron identification • The main difficulty for the positron measurement is the interacting-proton background: • fluctuations in hadronic shower development p0 ggmight mimic pure e.m. showers • proton spectrum harder than positron  p/e+ increase for increasing energy Energy-rigidity match e- ( e+ ) Energy measured in Calo/ Deflection in Tracker (MIP/GV)  ‘electrons’  ‘hadrons’ p-bar p Oscar Adriani ISVHECRI 2008

  20. e+ background estimation from data Rigidity: 6-8 GV Preliminary e- e+ p ‘presampler’ p Fraction of charge released along the calorimeter track (left, hit, right) + • Energy-momentum match • Starting point of shower Oscar Adriani ISVHECRI 2008

  21. Charge sign dependent solar modulation ¯ + Positrons to Electrons ratio Preliminary ___ Moskalenko & Strong 1998 statistical errors only Oscar Adriani ISVHECRI 2008

  22. Conclusions • PAMELA is continously taking data since July 2006 • Presented preliminary results from ~600 days of data: • Antiproton charge ratio (~1 GeV ÷100 GeV) • no evident deviations from secondary expectations • more data to come at lower and higher energies (up to ~150 GeV) • Positron charge ratio (~400 MeV ÷10 GeV) • indicates charge dependent modulation effects • more data to come at lower and higher energies (up to ~200 GeV) • Galactic primary proton spectra • primary spectra up to Z=8 to come • Galactic secondary-to-primary ratio (B/C) • abundance of other secondary elements (Li,Be) and isotopes (d,3He) to come • High energy tail of proton SEP events • spectra of other components (electrons, isotopes,…) to come • PAMELA is already providing significant experimental results, which will help in understanding CR origin and propagation • More exciting results will come in the next future! Oscar Adriani ISVHECRI 2008

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