Antimatter in Space Antimatter in Space Mirko Boezio INFN Trieste, Italy PPC Torino July 14 th 2010

Astrophysics and Cosmology compelling Issues Apparent absence of cosmological Antimatter Nature of the Dark Matter that pervades the Universe

CR + ISM  p-bar + … kinematic treshold: 5.6 GeV for the reaction

Background: CR interaction with ISM CR + ISM  p-bar + …

leaky box dinamic halo m  =20GeV Tilka 89 Balloon data : Positron fraction before 1990

What about heavy antinuclei? The discovery of one nucleus of antimatter (Z≥2) in the cosmic rays would have profound implications for both particle physics and astrophysics. o For a Baryon Symmetric Universe Gamma rays limits put any domain of antimatter more than 100 Mpc away (Steigman (1976) Ann Rev. Astr. Astrophys., 14, 339; Dudarerwicz and Wolfendale (1994) M.N.R.A. 268, 609, A.G. Cohen, A. De Rujula and S.L. Glashow, Astrophys. J. 495, 539, 1998)

Antimatter Search: current limits

P. Gondolo, IDM 2008

DM annihilations DM particles are stable. They can annihilate in pairs. Primary annihilation channels Decay Final states σ= σ a =

  p, e + - You are here - PAMELA p CR p ISM p, e + - Signal Background e +, e - ? Pulsar

Antimatter and Dark Matter Research BESS (93, 95, 97, 98, 2000) BESS (93, 95, 97, 98, 2000) Heat (94, 95, 2000) Heat (94, 95, 2000) IMAX (96) IMAX (96) BESS LDF (2004, 2007) BESS LDF (2004, 2007) AMS-01 (1998) AMS-01 (1998) Wizard Collaboration MASS – 1,2 (89,91) MASS – 1,2 (89,91) TrampSI (93) TrampSI (93) CAPRICE (94, 97, 98) CAPRICE (94, 97, 98) PAMELA (2006-) PAMELA (2006-)

CR antimatter Antiprotons Positrons CR + ISM  ± + x   ± + x  e ± + x CR + ISM   0 + x    e ± ___ Moskalenko & Strong 1998 Positron excess? Charge-dependent solar modulation Solar polarity reversal 1999/2000 Asaoka Y. Et al ¯ + CR + ISM  p-bar + … kinematic treshold: 5.6 GeV for the reaction Status in 2006

Moskalenko & Strong 1998 CR Antimatter: available data Why in space? Antiprotons BESS-polar (long-duration) “Standard” balloon- borne experiments low exposure (~days)  large statistical errors Atmospheric overburden (~5g/cm2)  additional systematic uncertainty (secondary production and particle losses) Positrons

What do we need? Measurements at higher energies Better knowledge of background High statistic Continuous monitoring of solar modulation Long Duration Flights

Antimatter Missions in Space P AMELA AMS /2011 GAPS 2013 AMS

AMS A LPHA M AGNETIC S PECTROMETER  Search for primordial anti-matter  Indirect search of dark matter  High precision measurement of the energetic spectra and composition of CR from GeV to TeV AMS-01: 1998 (10 days) PRECURSOR FLIGHT ON THE SHUTTLE AMS-02: 2010/2011 COMPLETE CONFIGURATION FOR SEVERAL YEARS LIFETIME ON THE ISS » 500 physicists, 16 countries, 56 Institutes

AMS-01 : the detector Acceptance:  » 0.15 m 2 sr Bending power » 0.14 Tm 2 TOF : trigger +  e dE/dx meas. Tracker: sign Z + Rigidità + dE/dx meas. Cherenkov: separatione e/p up to ~ 3 GeV.

The Completed AMS Detector on ISS Transition Radiation Detector (TRD) Silicon Tracker Electromagnetic Calorimeter (ECAL) Magnet Ring Image Cerenkov Counter (RICH) Time of Flight Detector (TOF) Size: 3m x 3m x 3m Weight: 7 tons

AMS-02 new configuration

PAMELA Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics

PAMELA Collaboration Moscow St. Petersburg Russia: Sweden: KTH, Stockholm Germany: Siegen Italy: BariFlorenceFrascatiTriesteNaplesRome CNR, Florence

Scientific goals Search for dark matter annihilation Search for antihelium (primordial antimatter) Search for new Matter in the Universe (Strangelets?) Study of cosmic-ray propagation (light nuclei and isotopes) Study of electron spectrum (local sources?) Study solar physics and solar modulation Study terrestrial magnetosphere

Design Performance energy range Antiprotons 80 MeV GeV Positrons 50 MeV – 300 GeV Electrons up to 500 GeV Protons up to 700 GeV Electrons+positrons up to 2 TeV (from calorimeter) Light Nuclei (He/Be/C) up to 200 GeV/n AntiNuclei search sensitivity of 3x10 -8 in He/He  Simultaneous measurement of many cosmic-ray species  New energy range  Unprecedented statistics

Resurs-DK1: multi-spectral imaging of earth’s surface PAMELA mounted inside a pressurized container Lifetime >3 years (assisted, first time February 2009) Data transmitted to NTsOMZ, Moscow via high-speed radio downlink. ~16 GB per day Quasi-polar and elliptical orbit (70.0°, 350 km km) Traverses the South Atlantic Anomaly Crosses the outer (electron) Van Allen belt at south pole Resurs-DK1 Mass: 6.7 tonnes Height: 7.4 m Solar array area: 36 m km 610 km 70 o PAMELA SAA ~90 mins Resurs-DK1 satellite + orbit

Main antenna in NTsOMZ Launch from Baikonur  June 15 th 2006, 0800 UTC. ‘First light’  June 21 st 2006, 0300 UTC. Detectors operated as expected after launch Different trigger and hardware configurations evaluated  PAMELA in continuous data-taking mode since commissioning phase ended on July 11 th 2006 Trigger rate* ~25Hz Fraction of live time* ~ 75% Event size (compressed mode) ~5kB 25 Hz x 5 kB/ev  ~ 10 GB/day (*outside radiation belts) Till ~now: ~1400 days of data taking ~20 TByte of raw data downlinked >2x10 9 triggers recorded and analyzed (Data till January 2010 under analysis) PAMELA milestones

PAMELA detectors GF: 21.5 cm 2 sr Mass: 470 kg Size: 130x70x70 cm 3 Power Budget: 360W Spectrometer microstrip silicon tracking system + permanent magnet It provides: - Magnetic rigidity  R = pc/Ze - Charge sign - Charge value from dE/dx 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 X 0, 0.6 λI) - Discrimination e+ / p, anti-p / e - (shower topology) - Direct E measurement for e - Neutron detector 3 He tubes + polyethylene moderator: - High-energy e/h discrimination Main requirements  high-sensitivity antiparticle identification and precise momentum measure + -

Antiparticles with PAMELA

Antiproton to Proton Flux Ratio Donato et al. (PRL 102 (2009) ) Simon et al. (ApJ 499 (1998) 250)Ptuskin et al. (ApJ 642 (2006) 902) Adriani et al., accepted for publication in PRL; arXiv:

Antiproton Flux Donato et al. (ApJ 563 (2001) 172) Ptuskin et al. (ApJ 642 (2006) 902) Adriani et al., accepted for publication in PRL; arXiv:

Trapped pbar, SAA GCR PAMELA Preliminary

Positron to Electron Fraction Secondary production Moskalenko & Strong 98 Adriani et al, Astropart. Phys. 34 (2010) 1 arXiv: [astro-ph.HE]

Solar modulation July 2006 August 2007 February 2008 PAMELA ¯ + ¯ + A-A- A+A+ A+A+ A-A- Decreasing solar activity Increasing flux ~11 y Low fluxes! PAMELA

But antiprotons in CRs are in agreement with secondary production Uncertainties on: Secondary production (primary fluxes, cross section) Propagation models Electron spectrum A Challenging Puzzle for CR Physics

P.Blasi, PRL 103 (2009) ; arXiv: Positrons (and electrons) produced as secondaries in the sources (e.g. SNR) where CRs are accelerated. I. Cholis et al., Phys. Rev. D 80 (2009) ; arXiv: v1 Contribution from DM annihilation. D. Hooper, P. Blasi, and P. Serpico, JCAP 0901:025,2009; arXiv: Contribution from diffuse mature &nearby young pulsars.

Conclusions Astroparticle physics from space is a fascinating field, fertile and rich of scientific potentials. Several very important esperiments are, or going to, directly measuring cosmic rays and their antimatter component: PAMELA, AMS Important results have already been published and soon more will come. Stay tuned, interesting times ahead!