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Understanding Cosmic-Rays with the PAMELA Experiment
Mirko BoezioINFN Trieste, Italy
On behalf of the PAMELA collaborationSILAFAE , Valparaiso
December 7th 2010
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Isotopic composition
[ACE]Solar Modulation
[PAMELA,ULYSSES
] AntimatterAntimatter
Dark MatterDark Matter[BESS, PAMELA, AMS]
Elemental Composition
[CREAM, ATIC, TRACER, NUCLEON,CALET, GAMMA-400?]
Extreme Energy CR[AUGER, EUSO, TUS/KLYPVE, OWL??]
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Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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PAMELAPAMELAPPayload for ayload for AAntimatter ntimatter MMatter atter EExploration xploration
and and LLight Nucleiight Nuclei AAstrophysicsstrophysics
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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PAMELA CollaborationPAMELA Collaboration
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Scientific goalsScientific goalsScientific goalsScientific 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
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Design PerformanceDesign 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
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PAMELA ApparatusPAMELA Apparatus
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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PAMELA detectorsPAMELA detectors
GF: 21.5 cm2 sr Mass: 470 kgSize: 130x70x70 cm3
Power Budget: 360W
Spectrometer microstrip silicon tracking system + permanent magnetIt provides:
- Magnetic rigidity R = pc/Ze- Charge sign- Charge value from dE/dx
Time-Of-Flightplastic scintillators + PMT:- Trigger- Albedo rejection;- Mass identification up to 1 GeV;- Charge identification from dE/dX.
Electromagnetic calorimeterW/Si sampling (16.3 X0, 0.6 λI)
- Discrimination e+ / p, anti-p / e- (shower topology)- Direct E measurement for e-
Neutron detector3He tubes + polyethylene moderator:- High-energy e/h discrimination
Main requirements high-sensitivity antiparticle identification and precise momentum measure+ -
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PAMELA INTEGRATION in the RESURS-DK1 satellite
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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• 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 - 600 km)
• Traverses the South Atlantic Anomaly • Crosses the outer (electron) Van Allen belt at south pole
Resurs-DK1Mass: 6.7 tonnesHeight: 7.4 mSolar array area: 36 m2
350 km
610 km
70o
PAMELA
SAA
~90 mins
Resurs-DK1 satellite + Resurs-DK1 satellite + orbitorbit
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Download @orbit 3754 – 15/02/2007 07:35:00 MWT
S1 S2 S3
orbit 3752 orbit 3753orbit 3751
NP SP
EQ EQ
95 min
Outer radiation belt
Inner radiation belt
(SSA)
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Subcutoff particlesSubcutoff particles
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Main antenna in NTsOMZ
Launch from Baikonur June 15th 2006, 0800 UTC.
‘First light’ June 21st 2006, 0300 UTC.
• Detectors operated as expected after launch• Different trigger and hardware configurations evaluated
PAMELA in continuous data-taking mode sincecommissioning phase ended on July 11th 2006
Trigger rate* ~25HzFraction 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>2x109 triggers recorded and analyzed
PAMELA milestones
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Particle ID with PAMELAParticle ID with PAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Flight data: 0.169 GV electron
Flight data: 0.171 GV positron
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Flight data: 0.763 GeV/cantiproton annihilation
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Bending in spectrometer: sign of chargeIonisation 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+ ~103-
4)
Antiproton (NB: e-/p ~ 102)
Antiproton / Positron Antiproton / Positron Identification Identification
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Flight data: 14.7 GVInteracting nucleus
(Z = 8)
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Cosmic Ray SpectraCosmic Ray Spectra
Cosmic-Ray Acceleration and Propagation in the Galaxy
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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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 PhysicsA Challenging Puzzle for CR Physics
GALPROP
Nature 458 (2009) 607; Astropart. Phys. 34 (2010) 1.
PRL 102, (2009) 051101; PRL 105 (2010) 121101.
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Diffusion Halo ModelDiffusion Halo Model
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PAMELA
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Proton and Helium Nuclei Proton and Helium Nuclei SpectraSpectra
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Proton and Helium Nuclei Proton and Helium Nuclei SpectraSpectra
GALPROP
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Proton and Helium Nuclei Proton and Helium Nuclei SpectraSpectra
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Boron and Carbon nuclei Boron and Carbon nuclei SpectraSpectraCarbon Boron
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Secondary nucleiSecondary nuclei
• B nuclei of secondary origin: CNO + ISM B + …
• Local secondary/primary ratio sensitive to average amount of traversed matter (lesc) from the source to the solar system
Local secondary abundance: study of galactic CR propagation
(B/C used for tuning of propagation models)
SPescP
S σλNN
LBM
Preliminary
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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0.9 GV < R < 1 GV
p
d
H isotopes separationH isotopes separation
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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PAMELA d/pPAMELA d/pPreliminary
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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PAMELA PAMELA 33He/He/44HeHePreliminary
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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ELECTRONSELECTRONS
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Positrons detectionWhere do positrons come from?
Mostly locally within 1 Kpc, due to the energy losses by Synchrotron Radiation and Inverse Compton
Typical lifetime
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Purposes of Electron Observations
Cygnus Loop20,000 years2,500 ly
Monogem86,000 years1,000 ly
Vela 10,000 years820 ly
Chandra
ROSAT
・CALET
Vela
近傍ソースの検出-エネルギースペクトル-到来方向の異方性
超新星における衝撃波加速加速機構と拡散過程超新星の頻度、分布
太陽変調
Anisotropy
W=1048 erg/SNI(E)=I0E-α
N =1/30yrD=D0(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< 105 years• L< 1 kpc
All Electron (e- + e+) spectra
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All three ATIC flights are consistentAll 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 sigmaJ Chang et al. Nature 456, 362 (2008)
Significance for ATIC1+2+4 is 5.1 sigma
ATIC 1+2+4
Preliminary
ATIC 1ATIC 2ATIC 4
Preliminary
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Theoretical uncertainties on “standard” positron fraction
FERMI e+ + e- flux (2009)
FERMI all Electron FERMI all Electron SpectrumSpectrum
GALPROP
A. A. Abdo et al. (The Fermi LAT Collaboration), Phys. Rev. Lett. 102, 181101 (2009).
See A. Moiseev’s talk on Wednesday
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PAMELA electron (ePAMELA electron (e--) ) spectrumspectrum
Preliminary
e+ + e-
e-
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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PAMELA electron (ePAMELA electron (e--) ) spectrumspectrum
Preliminary
Tracker based
Calorimeter based
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Theoretical uncertainties on Theoretical uncertainties on “standard” positron fraction“standard” positron fraction
T. Delahaye et al., arXiv: 0809.5268v3
γ = 3.54 γ = 3.34
Flux=A • E-
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PAMELA electron (ePAMELA electron (e--) ) spectrumspectrum Preliminary
Flux=A • E-
= 3.18 ±0.05GALPROP
prediction from e- flux
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
“New Primary Contribution”
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Independently to the fit of the electron spectra, we also perform a χ2
comparison between the expected positron fraction from GALPROP simulation and PAMELA measurement of the positron fraction.
Confidence level, in parameter space (2;ϕ0) 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 spectrumFit of electron spectrum
90%
95%
99%
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Solar ModulationSolar Modulation
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Positron to Electron Positron to Electron FractionFraction
Secondary production Moskalenko & Strong 98
Adriani et al, Astropart. Phys. 34 (2010) 1 arXiv:1001.3522 [astro-ph.HE]
Solar Modulation?
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1
3 ln
Df f Q( r, p,f
f tt p
)f K VV v
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 2
2pp
1 f... ... p D
p pp
Transport equation for the transport, Transport equation for the transport, modulation and acceleration of cosmic rays in modulation and acceleration of cosmic rays in
the heliospherethe heliosphere
Courtesy of M. Potgieter
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Solar Modulation of Galactic Solar Modulation of Galactic Cosmic RaysCosmic Rays
Courtesy of M. Potgieter
PAMELAPAMELA
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Preliminar
y
Time Dependence of PAMELA Proton Time Dependence of PAMELA Proton FluxFlux
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Preliminar
y
Time Dependence of PAMELA Proton Time Dependence of PAMELA Proton FluxFlux
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Preliminar
y
Time Dependence of PAMELA Electron Time Dependence of PAMELA Electron (e(e--) Flux) Flux
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Preliminar
y
Time Dependence of PAMELA Electron Time Dependence of PAMELA Electron (e(e--) Flux) Flux
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Flux variation as a function of time for rigidities between 0.72 and 1.04 GV
Time DependenceTime Dependence
Preliminar
y
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Increase of the flux measured by PAMELA from July 2006 to December 2008
Time DependenceTime Dependence
Preliminar
y
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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 PAMELA Electron to Positron Ratio and Theoretical ModelsModels
Preliminary
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Other PAMELA ResultsOther PAMELA Results
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Increase of low energy component
Solar Physics: December 13Solar Physics: December 13thth 2006 event 2006 eventfrom 2006-12-1 to 2006-12-4
from 2006-12-13 00:23:02 to 2006-12-13 02:57:46
from 2006-12-13 02:57:46 to 2006-12-13 03:49:09from 2006-12-13 03:49:09 to 2006-12-13 04:32:56
from 2006-12-13 04:32:56 to 2006-12-13 04:59:16from 2006-12-13 08:17:54 to 2006-12-13 09:17:34
Increase of low energy component
Decrease of high energy component
Preliminary
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--- M. Honda, 2008
Subcutoff particles spectra
@Kamioka
Atmospheric neutrino contribution
Astronaut dose on board ISS
Indirect measurement of cross section in the atmosphere
Agile e Glast background estimation
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SAA
SAA morphology
Lati
tud
eA
ltit
ud
e Altitude
Longitude
Neutron rate
South-Atlantic Anomaly (SAA)South-Atlantic Anomaly (SAA)
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Antiprotons inside SAAGalactic AntiprotonsAntiprotons below cutoff at equator
PAMELA trapped PAMELA trapped antiprotonsantiprotons
Preliminary
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Summary PAMELA ResultsSummary PAMELA Results
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
PAMELA Data
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SummarySummary• PAMELA has been in orbit and studying cosmic rays for ~4.5 years. >109 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.
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Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Spare SlidesSpare Slides
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Sign of charge, rigidity, dE/dx
Electron energy, dE/dx, lepton-hadron
separation
e- p -
e+ p (He,...)
Trigger, ToF, dE/dx
- +
GF ~21.5 cmGF ~21.5 cm2sr sr Mass: 470 kg Mass: 470 kg Size: 130x70x70 cmSize: 130x70x70 cm3
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Characteristics:• 5 modules of permanent magnet (Nd-B-Fe alloy) in aluminum mechanics
• Cavity dimensions 162x132x445 cm3 GF 21.5 cm2sr
• Magnetic shields• 5mm-step field-map • B=0.43 T (average along axis), B=0.48 T (@center)
The magnet
SPECTROMETER
PAMELA PAMELA
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The tracking system
Main tasks:• Rigidity measurement• Sign of electric charge• dE/dx
Characteristics:• 6 planes double-side (x&y view) microstrip Si sensors
• 36864 channels• Dynamic range 10 MIP
Performances:• Spatial resolution: 3÷4 m • MDR ~1.2TV (from flight data)SPECTROMETER
PAMELAPAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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The electromagnetic calorimeter
Main tasks:•e/h discrimination•e+/- energy measurement
Characteristics:•44 Si layers (X/Y) +22 W planes• 16.3 Xo / 0.6 l0
•4224 channels•Dynamic range ~1100 mip•Self-trigger mode (> 300 GeV GF~600 cm2 sr)
Performances:•p/e+ selection efficiency ~90%•p rejection factor 105
•e rejection factor >104
•Energy resolution ~5% @200GeVSPECTROMETER
CALORIMETER
PAMELA PAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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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)
CALORIMETER
PAMELA PAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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The anticounter shieldsMain 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
SPECTROMETERCALORIMETER
CARD
CAT
CAS
PAMELA PAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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S1
S2
S3
SPECTROMETER
CARD
CAT
CAS
Neutron detector
Main tasks:•e/h discrimination @high-energy
Characteristics:•36 3He counters: 3He(n,p)T Ep=780 keV•1cm thick polyetilene moderators• n collected within 200 ms time-window
Shower-tail catcher (S4)Main tasks:• ND triggerCharacteristics:•1 scintillator paddle 10mm thick
CALORIMETER
NEUTRON DETECTORS4
PAMELA PAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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The Launch: 15The Launch: 15thth June June 20062006
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The Launch: 15The Launch: 15thth June June 20062006
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Solar Modulation of Galactic Solar Modulation of Galactic Cosmic RaysCosmic Rays
BESS
Caprice / Mass /TS93AMS-01
Pamela• Study of charge sign dependent effects
Asaoka Y. et al. 2002, Phys. Rev. Lett. 88, 051101),
Bieber, J.W., et al. Physical Review Letters, 84, 674, 1999.
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
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Electrons measured with Electrons measured with H.E.S.S.H.E.S.S.
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Antiparticles with Antiparticles with PAMELAPAMELA
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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Antiproton to Proton Flux Antiproton to Proton Flux RatioRatio
Donato et al. (PRL 102 (2009) 071301)
Simon et al. (ApJ 499 (1998) 250) Ptuskin et al. (ApJ 642 (2006) 902)
Adriani et al., accepted for publication in PRL; arXiv:1007.0821
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Antiproton FluxAntiproton FluxDonato et al. (ApJ 563 (2001) 172)
Ptuskin et al. (ApJ 642 (2006) 902)
Adriani et al., accepted for publication in PRL; arXiv:1007.0821
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Positron to Electron Positron to Electron FractionFraction
Secondary production Moskalenko & Strong 98
Adriani et al, Astropart. Phys. 34 (2010) 1 arXiv:1001.3522 [astro-ph.HE]
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A Challenging Puzzle for CR PhysicsA Challenging Puzzle for CR Physics
P.Blasi, PRL 103 (2009) 051104; arXiv:0903.2794Positrons (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) 123518; arXiv:0811.3641v1
Contribution from DM annihilation.
D. Hooper, P. Blasi, and P. Serpico, JCAP 0901:025,2009; arXiv:0810.1527 Contribution from diffuse mature &nearby young pulsars.
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13 December 2006 Solar 13 December 2006 Solar FlareFlare
Helium fluxProton flux
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
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13 December 2006 Solar 13 December 2006 Solar FlareFlare
Mirko Boezio, SILAFAE, Valparaiso, 2010/12/07
Proton flux Helium flux