Understanding Cosmic-Rays with the PAMELA Experiment Mirko Boezio INFN Trieste, Italy On behalf of the PAMELA collaboration SILAFAE, Valparaiso December 7 th 2010

Isotopic composition [ACE] Solar Modulation [PAMELA,ULYSSES] Antimatter Dark Matter [BESS, PAMELA, AMS] Elemental Composition [CREAM, ATIC, TRACER, NUCLEON, CALET, GAMMA-400?] Extreme Energy CR [AUGER, EUSO, TUS/KLYPVE, OWL??]

Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

PAMELA Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

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

PAMELA Apparatus Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

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 + -

PAMELA INTEGRATION in the RESURS-DK1 satellite Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Resurs-DK1: multi-spectral imaging of earth’s surface PAMELA mounted inside a pressurized container Lifetime >3 years (assisted, first time February 2009), extended till end 2011 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

– 15/02/ :35:00 MWT S1 S2 S3 orbit 3752 orbit 3753 orbit 3751 NP SP EQ EQ 95 min Outer radiation belt Inner radiation belt (SSA)‏

Subcutoff particles Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

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 PAMELA milestones

Particle ID with PAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Flight data: GV electron Flight data: GV positron

Flight data: GeV/c antiproton annihilation

Bending in spectrometer: sign of charge Ionisation energy loss (dE/dx): magnitude of charge Interaction pattern in calorimeter: electron-like or proton-like, electron energy Time-of-flight: trigger, albedo rejection, mass determination (up to 1 GeV) Positron (NB: p/e + ~ ) Antiproton (NB: e - /p ~ 10 2 ) Antiproton / Positron Identification

Flight data: 14.7 GV Interacting nucleus (Z = 8)‏

Cosmic Ray Spectra Cosmic-Ray Acceleration and Propagation in the Galaxy Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

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 GALPROP Nature 458 (2009) 607; Astropart. Phys. 34 (2010) 1. PRL 102, (2009) ; PRL 105 (2010)

Diffusion Halo Model

PAMELA

Proton and Helium Nuclei Spectra

GALPROP

Proton and Helium Nuclei Spectra Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Boron and Carbon nuclei Spectra Carbon Boron Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Secondary nuclei B nuclei of secondary origin: CNO + ISM  B + … Local secondary/primary ratio sensitive to average amount of traversed matter (l esc ) from the source to the solar system Local secondary abundance:  study of galactic CR propagation (B/C used for tuning of propagation models) LBM Preliminary Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

0.9 GV < R < 1 GV p d H isotopes separation Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

PAMELA d/p Preliminary Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

PAMELA 3 He/ 4 He Preliminary Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

ELECTRONS

Positrons detection Where do positrons come from? Mostly locally within 1 Kpc, due to the energy losses by Synchrotron Radiation and Inverse Compton Typical lifetime

Purposes of Electron Observations Cygnus Loop 20,000 years 2,500 ly Monogem 86,000 years 1,000 ly Vela 10,000 years 820 ly Chandra ROSAT Anisotropy W=10 48 erg/SN I(E)=I 0 E -α Ｎ =1/30yr D=D 0 (E/TeV) 0.3 Search for the signature of nearby HE electron sources (believed to be SNR) in the electron spectrum above ~ TeV Search for anisotropy in HE electron flux as an effect of the nearby sources. Precise measurement of electron spectrum above 10 GeV to define a model of accele- ration and propagation. Observation of electron spectrum in 1~10 GeV for study of solar modulation Possible Nearby Sources T< 10 5 years L< 1 kpc All Electron (e - + e + ) spectra

All three ATIC flights are consistent ATIC-4 with 10 BGO layers has improved e, p separation. (~4x lower background) “Bump” is seen in all three flights. ATIC 1+2 “Source on/source off” significance of bump for ATIC1+2 is about 3.8 sigma J Chang et al. Nature 456, 362 (2008) Significance for ATIC1+2+4 is 5.1 sigma ATIC Preliminary ATIC 1 ATIC 2 ATIC 4 Preliminary

Theoretical uncertainties on “standard” positron fraction FERMI e + + e - flux (2009) FERMI all Electron Spectrum GALPROP A. A. Abdo et al. (The Fermi LAT Collaboration), Phys. Rev. Lett. 102, (2009). See A. Moiseev’s talk on Wednesday

PAMELA electron (e - ) spectrum Preliminary e + + e - e-e- Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

PAMELA electron (e - ) spectrum Preliminary Tracker based Calorimeter based Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Theoretical uncertainties on “standard” positron fraction T. Delahaye et al., arXiv: v3 γ = 3.54γ = 3.34 Flux=A E - 

PAMELA electron (e - ) spectrum Preliminary Flux=A E -   = 3.18 ±0.05 GALPROP prediction from e - flux Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07 “New Primary Contribution”

Independently to the fit of the electron spectra, we also perform a χ 2 comparison between the expected positron fraction from GALPROP simulation and PAMELA measurement of the positron fraction. Confidence level, in parameter space (  2 ; ϕ 0 ) obtained from a fit of the electron spectra ( red ) and of the positron fraction ( green ). Cruces show the best-fit combination. Interestingly, the best fit value for the two independent fit are very similar. Preliminary positron fraction electron spectrum Fit of electron spectrum 90% 95% 99% Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Solar Modulation Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

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

Time-dependent, pitch-angle-averaged distribution function Diffusion Convection with solar wind Particle Drifts Adiabatic energy changes Any local source Parker (Planet. Space Science, 13, 9,1965) Second order Fermi acceleration Transport equation for the transport, modulation and acceleration of cosmic rays in the heliosphere Courtesy of M. Potgieter

Solar Modulation of Galactic Cosmic Rays Courtesy of M. Potgieter PAMELA

Preliminary Time Dependence of PAMELA Proton Flux Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Preliminary Time Dependence of PAMELA Proton Flux Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Preliminary Time Dependence of PAMELA Electron (e - ) Flux Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Preliminary Time Dependence of PAMELA Electron (e - ) Flux Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Flux variation as a function of time for rigidities between 0.72 and 1.04 GV Time Dependence Preliminary

Increase of the flux measured by PAMELA from July 2006 to December 2008 Time Dependence Preliminary

Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07 U.W. Langner, M.S. Potgieter, Advances in Space Research 34 (2004). PAMELA Electron to Positron Ratio and Theoretical Models Preliminary

Other PAMELA Results Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Increase of low energy component Solar Physics: December 13 th 2006 event from to from :23:02 to :57:46 from :57:46 to :49:09 from :49:09 to :32:56 from :32:56 to :59:16 from :17:54 to :17:34 Increase of low energy component Decrease of high energy component Preliminary

--- M. Honda, 2008 Subcutoff particles  Atmospheric neutrino contribution  Astronaut dose on board ISS  Indirect measurement of cross section in the atmosphere  Agile e Glast background estimation

SAA SAA morphology Latitude Altitude Longitude Neutron rate South-Atlantic Anomaly (SAA)

Antiprotons inside SAA Galactic Antiprotons Antiprotons below cutoff at equator PAMELA trapped antiprotons Preliminary Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Summary PAMELA Results Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07 PAMELA Data

Summary PAMELA has been in orbit and studying cosmic rays for ~4.5 years. >10 9 triggers registered and >19 TB of data has been down-linked. Antiproton-to-proton flux ratio and antiproton energy spectrum (~100 MeV - ~200 GeV) show no significant deviations from secondary production expectations. High energy positron fraction (>10 GeV) increases significantly (and unexpectedly!) with energy. Primary source? The proton and helium nuclei spectra have been measured up to 1.2 TV. The observations challenge the current paradigm of cosmic ray acceleration and propagation. The e - spectrum up to 600 GeV shows spectral features that may point to additional components. Analysis ongoing to finalize the antiparticle measurements (positron flux, positron fraction), continuous study of solar modulation effects at low energy. Waiting for AMS to compare contemporary measurements.

Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Spare Slides Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Sign of charge, rigidity, dE/dx Electron energy, dE/dx, lepton-hadron separation e-e- p - e+e+ p (He,...)‏ Trigger, ToF, dE/dx - + GF ~21.5 cmsr Mass: 470 kg Size: 130x70x70 cm GF ~21.5 cm 2 sr Mass: 470 kg Size: 130x70x70 cm 3

Characteristics: 5 modules of permanent magnet (Nd-B- Fe alloy) in aluminum mechanics Cavity dimensions 162x132x445 cm 3  GF 21.5 cm 2 sr Magnetic shields 5mm-step field-map B=0.43 T (average along axis), B=0.48 T The magnet SPECTROMETERPAMELA

The tracking system Main tasks: Rigidity measurement Sign of electric charge dE/dx Characteristics: 6 planes double-side (x&y view) microstrip Si sensors channels Dynamic range 10 MIP Performances: Spatial resolution: 3÷4  m MDR ~1.2TV (from flight data) SPECTROMETERPAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

The electromagnetic calorimeter Main tasks: e/h discrimination e +/- energy measurement Characteristics: 44 Si layers (X/Y) +22 W planes 16.3 X o / 0.6 l channels Dynamic range ~1100 mip Self-trigger mode (> 300 GeV GF~600 cm 2 sr) Performances: p/e + selection efficiency ~90% p rejection factor 10 5 e rejection factor >10 4 Energy resolution SPECTROMETER CALORIMETERPAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

S1 S2 S3 SPECTROMETER The time-of-flight system Main tasks: First-level trigger Albedo rejection dE/dx Particle identification (<1GeV/c) Characteristics: 3 double-layer scintillator paddles X/Y segmentation Total: 48 Channels Performances:  paddle ~ 110ps  TOF ~ 330ps (for MIPs) CALORIMETERPAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

The anticounter shields Main tasks: Rejection of events with particles interacting with the apparatus (off-line and second- level trigger) Characteristics: scintillator paddles 10mm thick 4 up (CARD), 1 top (CAT), 4 side (CAS) Performances: Efficiency > 99.9% S1 S2 S3 SPECTROMETER CALORIMETER CARD CAT CASPAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

S1 S2 S3 SPECTROMETER CARD CAT CAS Neutron detector Main tasks: e/h Characteristics: 36 3 He counters: 3 He(n,p)T  Ep=780 keV 1cm thick polyetilene moderators n collected within 200 ms time-window Shower-tail catcher (S4) Main tasks: ND trigger Characteristics: 1 scintillator paddle 10mm thick CALORIMETER NEUTRON DETECTOR S4PAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

The Launch: 15 th June 2006

Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Solar Modulation of Galactic Cosmic Rays BESS Caprice / Mass /TS93 AMS-01 Pamela Study of charge sign dependent effects Asaoka Y. et al. 2002, Phys. Rev. Lett. 88, ), Bieber, J.W., et al. Physical Review Letters, 84, 674, J. Clem et al. 30th ICRC 2007 U.W. Langner, M.S. Potgieter, Advances in Space Research 34 (2004) Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Electrons measured with H.E.S.S. Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

Antiparticles with PAMELA Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

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:

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

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. But also other secondaries are produced: significant increase expected in the p/p and B/C ratios. 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.

13 December 2006 Solar Flare Helium fluxProton flux Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07

13 December 2006 Solar Flare Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07 Proton fluxHelium flux