Recent PAMELA Results

8/6/2019 Recent PAMELA Results

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Recent PAMELA Results

Mirko BoezioINFN Trieste, Italy

On behalf of the PAMELA collaboration

UCLA Dark Matter 2010

February 24th

2010


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Isotopic

composition

[ACE]

Solar Modulation

AntimatterDark Matter

[BESS, PAMELA, AMS]

ElementalComposition

[CREAM, ATIC, TRACER, NUCLEON,CALET, ACCESS?, INCA?,

Extreme Energy CR [AUGER, EUSO, TUS/KLYPVE, OWL??]


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Background:CR interaction with ISMCR + ISM p-bar +


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DM annihilationsDM particles are stable. They can annihilate in pairs.

Primary annihilationchannels Decay Final states

a= < v>


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PAMELAP ayload for Antimatter Matter Explorationand Light Nuclei Astrophysics


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PAMELA Collaboration

MoscowSt. Petersburg

Russia:

Sweden:KTH, Stockholm

Germany:Siegen

Italy:Bari Florence Frascati TriesteNaples Rome CNR, Florence


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Resurs-DK1: multi-spectralimaging of earths surface PAMELA mounted inside apressurized container

Lifetime >3 years (assisted, firsttime last February). Expected tillend 2011.

Data transmitted to NTsOMZ,Moscow via high-speed radiodownlink. ~16 GB per day

Quasi-polar and elliptical orbit(70.0 , 350 km - 600 km)

Traverses the South AtlanticAnomaly

Crosses the outer (electron) VanAllen belt at south pole

Resurs-DK1Mass: 6.7 tonnesHeight: 7.4 mSolar array area: 36 m 2

350 km

610 km

70 o

PAMELA

SAA

~90 mins

Resurs-DK1 satellite + orbit


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Subcutoff particles

Mirko Boezio, UCLA Dark Matter 2010,2010/02/24


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Antiparticle Results

Nature 458 (2009) 607,Astro-ph 0810.4995

PRL 102, (2009) 051101,Astro-ph 0810.4994

Mirko Boezio, UCLA DarkMatter 2010, 2010/02/24


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PAMELA detectors

GF: 21.5 cm 2 srMass: 470 kgSize: 130x70x70 cm 3Power Budget: 360W

Spectrometermicrostrip 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 1GeV;

- Charge identification fromdE/dX.

Electromagnetic calorimeterW/Si sampling (16.3 X 0, 0.6 I)

- Discrimination e+ / p, anti-p / e -(shower topology)

- Direct E measurement for e-

Neutron detector 3He tubes + polyethylene

moderator:- High-energy e/h discrimination

Main requirements high-sensitivity antiparticle identification and precise momentum measure+ -


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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 inspectrometer:sign of charge

Ionisation energyloss (dE/dx):magnitude of charge

Interactionpattern incalorimeter:electron-like orproton-like,electron energy

Time-of-flight:trigger, albedorejection, massdetermination(up to 1 GeV)

Positron(NB: p/e + ~10 3-4 )

Antiproton(NB: e -/p ~ 10 2)

Antiproton / positron identification


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e-

p

p

Calorimeterselection

Tracker Identification

Protons (& spillover)

Antiprotons

Strong track requirements:MDR > 850 GV


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Antiproton to proton flux ratio

Errors might beunderestimated,

possible residualspillover-protoncontamination


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Antiproton Flux

PAMELA

Errorsunderestimated,possible residualspillover-protoncontamination


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p (non-int)

e-

e+p (non-int)

Fraction of energy released along the calorimeter track (left, hit, right)

p (int)

p (int )

Rigidity: 20-30 GV

Positron selection with calorimeter

LEFT HIT RIGHT

strips

p l a n e s

0.6 R M

for em showers90% of E containedin 1 R M


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e-

Fraction of charge released along thecalorimeter track (left, hit, right)

p?e+?

+ Energy-momentum matchStarting point of shower

Rigidity: 20-30 GV



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Positron to Electron Fraction

In Nature article publisheddata acquired till February2008

New data reduction: data

till end of 2008. With sameapproach of Nature paper~30% increase in statisticsbetter understanding of systematics.

Secondary productionMoskalenko & Strong 98

Adriani et al, arXiv:1001.3522 [astro-ph.HE]


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Flight data: 51 GeV/cpositron


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e-

Fraction of charge released along thecalorimeter track (left, hit, right)

p

e+

+ Energy-momentum match Starting point of shower Longitudinal profile

Rigidity: 20-30 GV


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PAMELA Positron Fraction

But how reliableis this curve?



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Diffusion Halo Model



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Galactic H and He spectra

proton

He


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Proton Spectrum


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Helium Nuclei Spectrum


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Secondary nuclei

B nuclei of secondary origin:CNO + ISM B +

Local secondary/primary ratio sensitive toaverage 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)

SPescP

S NN

LBM


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Antiprotons

Mirko Boezio, UCLA DarkMatter 2010, 2010/02/24

Errors might beunderestimated,possible residualspillover-protoncontamination

Antiprotons in

CRs are inagreement withsecondaryproduction


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Positrons detectionWhere do positrons come from?

Mostly locally within 1 Kpc, due to the energy losses bySynchrotron Radiation and Inverse Compton

Typical lifetime


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PAMELA Positron Fraction



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M. Cirelli et al., Nucl.Phys. B 813 (2009) 1;arXiv: 0809.2409v3 Interpretation: DM

Which DM spectra can fit the data?

DM with and dominantannihilation channel ( possible candidate: Wino )

positrons antiprotons


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Interpretation: DMWhich DM spectra can fit the data?DM with and dominant

annihilation channel ( no natural SUSY candidate )positrons antiprotons

But B 10 4

M. Cirelli et al., Nucl.Phys. B 813 (2009) 1;arXiv: 0809.2409v3


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Interpretation: DM

DM with and dominantannihilation channel

positronsantiprotons

M. Cirelli et al., Nucl.Phys. B 813 (2009) 1;arXiv: 0809.2409v3


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I Cholis et al Phys Rev D 80 (2009)


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Interpretation: DMI. Cholis et al. Phys. Rev. D 80 (2009)

123518; arXiv:0811.3641v1


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Interpretation: DM

P. Grajek et al., Phys. Rev. D 79 (2009)043506; arXiv: 0812.4555v1Non-thermal wino-like neutralinoVarying propagation model, no boostfactor


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Astrophysical Explanation: SNR

P.Blasi, arXiv:0903.2794 [astro-ph]

Positrons (andelectrons) producedas secondaries inthe sources (e.g.SNR) where CRsare accelerated.But also othersecondaries areproduced:significant increaseexpected in the p/pand B/C ratios.


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Mechanism: the spinning B of the pulsar strips e-

thataccelerated at the polar cap or at the outer gap emit thatmake production of e that are trapped in the cloud,further accelerated and later released at ~ 10 5 years.

Young (T < 10 5 years) and nearby (< 1kpc) If not: too much diffusion, low energy, too low flux.

Geminga: 157 parsecs from Earth and 370,000 years old B0656+14: 290 parsecs from Earth and 110,000 years old.

Diffuse mature pulsars

Astrophysical Explanation:Pulsars

Astrophysical Explanation:


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Astrophysical Explanation:Pulsars

H. Yksak et al., arXiv:0810.2784v2Contributions of e- & e+ fromGeminga assuming different distance,age and energetic of the pulsar

diffuse mature &nearby young pulsarsHooper, Blasi, and SerpicoarXiv:0810.1527


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PAMELA Electron (e -) Spectrum



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El fl b k i h ?

PAMELA El t ( -) S t


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Electron flux - break in the spectrum?PAMELA Electron (e -) Spectrum



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Summary


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SummaryPAMELA has been in orbit and studying cosmic rays for ~42 months.

>109

triggers registered and >18 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 secondaryproduction expectations.

High energy positron fraction (>10 GeV) increases significantly (andunexpectedly!) with energy. Primary source?Data at higher energies might help to resolve origin of rise (spilloverlimit ~300 GeV).

e- spectrum up to ~200 GeV shows spectral features that may point toadditional components. Analysis is ongoing to increase the statistics andexpand the measurement of the e- spectrum up to ~500 GeV and e+

spectrum up to ~300 GeV ( all electrum (e - + e +) spectrum up to ~1 TV).

Furthemore: PAMELA is going to provide measurements on elemental spectra and low mass isotopes with an unprecedentedstatistical precision and is helping to improve the understanding of particle propagation in the interstellar medium

PAMELA is able to measure the high energy tail of solar particles. PAMELA is going to set a new lower limit for finding Antihelium

http://pamela.roma2.infn.it
http://pamela.roma2.infn.it/http://pamela.roma2.infn.it/


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Mi k B i UCLA D k M tt 2010

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Recent PAMELA Results