Antimatter in Space Mirko Boezio INFN Trieste, Italy PPC 2010 - 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 +
Balloon data : Positron fraction before 1990 m χ =20GeV Tilka 89 dinamic halo leaky box
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 a = <σv> <
Background p CR p ISM - p, e + χ You are here - p, e + - χ Signal e +, e -? Pulsar PAMELA
Antimatter and Dark Matter Research Wizard Collaboration MASS 1,2 (89,91) TrampSI (93) CAPRICE (94, 97, 98) PAMELA (2006-) BESS (93, 95, 97, 98, 2000) Heat (94, 95, 2000) IMAX (96) BESS LDF (2004, 2007) AMS-01 (1998)
Charge-dependent solar modulation Asaoka Y. Et al. 2002 CR antimatter Solar polarity reversal 1999/2000 Antiprotons Status in 2006 Positrons Moskalenko & Strong 1998 Positron excess? + CR + ISM p-bar + kinematic treshold: 5.6 GeV for the reaction pp pppp CR + ISM π ± + x µ ± + x e ± + x CR + ISM π 0 + x γγ e ±
CR Antimatter: available data Why in space? Antiprotons Positrons Moskalenko & Strong 1998 BESS-polar (long-duration) low exposure (~days) large statistical errors Atmospheric overburden (~5g/cm2) additional systematic uncertainty (secondary production and particle losses) Standard balloonborne experiments
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 PAMELA 15-06-2006 AMS-01 1998 AMS-02 2010/2011 GAPS 2013
ALPHA MAGNETIC SPECTROMETER 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: Ω» 0.15 m 2 sr Bending power» 0.14 Tm 2 TOF : trigger + β e de/dx meas. Tracker: sign Z + Rigidità + de/dx meas. Cherenkov: separatione e/p up to ~ 3 GeV.
Transition Radiation Detector (TRD) The Completed AMS Detector on ISS Time of Flight Detector (TOF) Silicon Tracker Magnet Electromagnetic Calorimeter (ECAL) Ring Image Cerenkov Counter (RICH) 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
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 - 190 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 satellite + orbit PAMELA Resurs-DK1 Mass: 6.7 tonnes Height: 7.4 m Solar array area: 36 m 2 350 km 70 o 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 - 600 km) SAA ~90 mins 610 km Traverses the South Atlantic Anomaly Crosses the outer (electron) Van Allen belt at south pole
PAMELA milestones 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 Main antenna in NTsOMZ 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 detectors Main requirements high-sensitivity antiparticle identification and precise momentum measure 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 - + - GF: 21.5 cm 2 sr Mass: 470 kg Size: 130x70x70 cm 3 Power Budget: 360W Neutron detector 3 He tubes + polyethylene moderator: - High-energy e/h discrimination Spectrometer microstrip silicon tracking system + permanent magnet It provides: - Magnetic rigidity R = pc/ze - Charge sign - Charge value from de/dx
Antiparticles with PAMELA
Antiproton to Proton Flux Ratio Simon et al. (ApJ 499 (1998) 250) Ptuskin et al. (ApJ 642 (2006) 902) Donato et al. (PRL 102 (2009) 071301) Adriani et al., accepted for publication in PRL; arxiv:1007.0821
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:1007.0821
Trapped pbar, SAA PAMELA GCR PAMELA Preliminary Preliminary Preliminary Preliminary
Positron to Electron Fraction Secondary production Moskalenko & Strong 98 Adriani et al, Astropart. Phys. 34 (2010) 1 arxiv:1001.3522 [astro-ph.he]
Solar modulation A + A - A + A - ~11 y Low fluxes! PAMELA + Increasing flux PAMELA July 2006 August 2007 February 2008 Decreasing solar activity +
A Challenging Puzzle for CR Physics Uncertainties on: Secondary production (primary fluxes, cross section) Propagation models Electron spectrum But antiprotons in CRs are in agreement with secondary production
A Challenging Puzzle for CR Physics P.Blasi, PRL 103 (2009) 051104; arxiv:0903.2794 Positrons (and electrons) produced as secondaries in the sources (e.g. SNR) where CRs are accelerated. D. Hooper, P. Blasi, and P. Serpico, JCAP 0901:025,2009; arxiv:0810.1527 Contribution from diffuse mature &nearby young pulsars. I. Cholis et al., Phys. Rev. D 80 (2009) 123518; arxiv:0811.3641v1 Contribution from DM annihilation.
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-2010... Important results have already been published and soon more will come. Stay tuned, interesting times ahead!