understanding cosmic-rays with the pamela experiment mirko boezio infn trieste, italy on behalf of...

Understanding Cosmic-Rays with the PAMELA Experiment

Mirko BoezioINFN Trieste, Italy

On behalf of the PAMELA collaborationSILAFAE , Valparaiso

December 7th 2010

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??]

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

PAMELAPAMELAPPayload for ayload for AAntimatter ntimatter MMatter atter EExploration xploration

and and LLight Nucleiight Nuclei AAstrophysicsstrophysics


PAMELA CollaborationPAMELA Collaboration

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

http://www.noaanews.noaa.gov/stories2005/images/sun-soho011905-1919z2.jpg

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

PAMELA ApparatusPAMELA Apparatus


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+ -

PAMELA INTEGRATION in the RESURS-DK1 satellite


• 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

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)

Subcutoff particlesSubcutoff particles


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

Particle ID with PAMELAParticle ID with PAMELA


Flight data: 0.169 GV electron

Flight data: 0.171 GV positron

Flight data: 0.763 GeV/cantiproton annihilation

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

Flight data: 14.7 GVInteracting nucleus

(Z = 8)

Cosmic Ray SpectraCosmic Ray Spectra

Cosmic-Ray Acceleration and Propagation in the Galaxy


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.

Diffusion Halo ModelDiffusion Halo Model

PAMELA

Proton and Helium Nuclei Proton and Helium Nuclei SpectraSpectra


GALPROP

Boron and Carbon nuclei Boron and Carbon nuclei SpectraSpectraCarbon Boron


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


0.9 GV < R < 1 GV

p

d

H isotopes separationH isotopes separation


PAMELA d/pPAMELA d/pPreliminary


PAMELA PAMELA 33He/He/44HeHePreliminary


ELECTRONSELECTRONS


Positrons detectionWhere 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 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

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

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

PAMELA electron (ePAMELA electron (e--) ) spectrumspectrum

Preliminary

e+ + e-

e-


PAMELA electron (ePAMELA electron (e--) ) spectrumspectrum

Preliminary

Tracker based

Calorimeter based


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-

PAMELA electron (ePAMELA electron (e--) ) spectrumspectrum Preliminary

Flux=A • E-

= 3.18 ±0.05GALPROP

prediction from e- flux


“New Primary Contribution”

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%


Solar ModulationSolar Modulation


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?

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

Solar Modulation of Galactic Solar Modulation of Galactic Cosmic RaysCosmic Rays

Courtesy of M. Potgieter

PAMELAPAMELA

Preliminar

y

Time Dependence of PAMELA Proton Time Dependence of PAMELA Proton FluxFlux


Preliminar

y

Time Dependence of PAMELA Electron Time Dependence of PAMELA Electron (e(e--) Flux) Flux


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

Time DependenceTime Dependence

Preliminar

y

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

Time DependenceTime Dependence

Preliminar

y


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

Other PAMELA ResultsOther PAMELA Results


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

--- 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

SAA

SAA morphology

Lati

tud

eA

ltit

ud

e Altitude

Longitude

Neutron rate

South-Atlantic Anomaly (SAA)South-Atlantic Anomaly (SAA)

Antiprotons inside SAAGalactic AntiprotonsAntiprotons below cutoff at equator

PAMELA trapped PAMELA trapped antiprotonsantiprotons

Preliminary


Summary PAMELA ResultsSummary PAMELA Results


PAMELA Data

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.

Spare SlidesSpare Slides


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

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

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


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


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


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


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


The Launch: 15The Launch: 15thth June June 20062006

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)


Electrons measured with Electrons measured with H.E.S.S.H.E.S.S.


Antiparticles with Antiparticles with PAMELAPAMELA


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

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

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]

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.

13 December 2006 Solar 13 December 2006 Solar FlareFlare

Helium fluxProton flux


13 December 2006 Solar 13 December 2006 Solar FlareFlare


Proton flux Helium flux

understanding cosmic-rays with the pamela experiment mirko boezio infn trieste, italy on behalf of...

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