Bruno-sost Vulc 2010 01 - Laboratori Nazionali di Frascati · 2010-06-04 · •Geminga: 157 parsecs from Earth and 370,000 years old •B0656+14: 290 parsecs from Earth and 110,000

PAMELAAMELAannihilation of dark matter annihilation of dark matter particlesparticles

and astrophysical sourcesand astrophysical sources

Alessandro BrunoINFN Bari, Italy

On behalf of the PAMELA collaboration

Vulcano Workshop 2010Frontier Objects in Astrophysics and Particle Physics

May 24-29, Vulcano, Italy

A. Bruno 2Vulcano Workshop, 24-29 May 2010

Bari Florence Frascati

Italy:TriesteNaple

sRome CNR, Florence

Moscow St. Petersburg

Russia:

Germany:Siegen

Sweden:KTH, Stockholm

The PAMELA collaborationThe PAMELA collaboration

• 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

Scientific goalsScientific goals


Design PerformancesDesign Performances 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

Simultaneousmeasurementofmanycosmic‐rayspecies Newenergyrange Unprecedentedsta8s8cs


PAMELA detectorsPAMELA detectors

GF: 21.5 cm2 srMass: 470 kgSize: 130x70x70 cm3

Power Budget: 360W

Spectrometermicrostrip silicon tracking system + permanent magnet

Time-Of-Flightplastic scintillators + PMT:- Trigger- Albedo rejection;- Mass identification up to 1GeV;- Charge identification fromdE/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 counters- High-energy e/h discrimination

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

It provides:•Magnetic rigidity R = pc/Ze•Charge sign•Charge value from dE/dx

Performances:•Spatial resolution: 3÷4 mm•MDR ~1.2TV (from flight data)


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

PAMELAPAMELA

The tracking system

Main tasks:• Rigidity measurement• Sign of electric charge• dE/dxCharacteristics:• 6 planes double-side (x&y view) microstripSi sensors

• 36864 channels• Dynamic range 10 MIPPerformances:• Spatial resolution: 3÷4 µm• MDR ~1.2TV (from flight data)SPECTROMETER

PAMELAPAMELA

Vulcano Workshop, 24-29 May 2010A. Bruno 7

The electromagnetic calorimeter

Main tasks:•e/h discrimination•e+/- energy measurementCharacteristics:•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

PAMELAPAMELA


A. Bruno Vulcano Workshop, 24-29 May 2010

• Resurs-DK1: multi-spectralimaging of earth’s surface• PAMELA mounted inside apressurized container

• Lifetime >3 years

• 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 m2

350 km

610 km

70o

PAMELA

SAA

~90 mins~90 mins

Resurs-DK1 satellite + orbitResurs-DK1 satellite + orbit

9

Antiparticles with PAMELAAntiparticles with PAMELA


Bending inspectrometer:sign of charge

Ionisation energyloss (dE/dx):magnitude ofcharge

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

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

Positron(NB: p/e+ ~103-4)

Antiproton(NB: e-/p ~ 102)

Antiparticle identificationAntiparticle identification


ANTIPROTONSANTIPROTONS

Antiproton to proton ratioAntiproton to proton ratio


Preliminary

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

Antiproton to proton ratioAntiproton to proton ratio


Preliminary

Antiproton FluxAntiproton Flux


Preliminary

POSITRONSPOSITRONS

Positron to Electron FractionPositron to Electron Fraction

In Nature article publisheddata acquired till February2008

New data reduction: datatill end of 2008. With sameapproach of Nature paper~30% increase in statisticsbetter understanding ofsystematics.

Secondary productionMoskalenko & Strong 98

Adriani et al, arXiv:1001.3522 [astro-ph.HE]A. Bruno 17Vulcano Workshop, 24-29 May 2010

PAMELA data:PAMELA data: astrophysical and DM scenarios astrophysical and DM scenarios


PAMELA antiproton dataPAMELA antiproton data

Antiprotons inCRs are inagreement withsecondaryproduction


Secondary productionMoskalenko & Strong 98

GALPROP


PAMELA positron fractionPAMELA positron fraction

A. Bruno Vulcano Workshop, 24-29 May 2010 21

Theoretical uncertainties on Theoretical uncertainties on ““standardstandard””positron fractionpositron fraction

T. Delahaye et al., arXiv: 0809.5268v3

γ = 3.54 γ = 3.34


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

Interpretation:Interpretation:DMDMWhich DM spectracan fit the data?

From the PAMELA data alone,two solutions emerge:1)either the DM particles thatannihilate into W;Z; h must beheavier than about 10 TeV;2)or the DM must annihilate onlyinto leptons.

Thus in both cases a DM particlecompatible with the PAMELAexcess seems to have quiteunexpected properties.

Interpretation: DMInterpretation: DM


models where darkmatter only pairannihilates into chargedleptons can give asatisfactory fit to thedata for dark matterparticle massesbetween 0.4 and 2 TeV,and for boost factors onthe order of 102.

D. Grasso et al. Astrop. Phys. 32 (2009), arXiv: 0905.0636v3

Constraints on parameter space from PAMELA and FERMI dataConstraints on parameter space from PAMELA and FERMI data


The parameter space of particle dark mattermass versus pair-annihilation rate, for models: DM annihilatating into monochromatic e±; “lepto-philic” models, where the dark matter pairannihilates democratically into the three chargedlepton species. heavy dark matter pair-annihilating intoelectro-weak gauge bosons.

D. Grasso et al. Astrop. Phys. 32(2009), arXiv: 0905.0636v3




G. Kane et al., Phys. Rev. B 681(2009)arXiv: 0906.4765v3Non-thermal wino-like neutralinoVarying propagation model, no boostfactor



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

123518; arXiv:0811.3641v1


Astrophysical Explanation: SNRAstrophysical Explanation: SNR

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

Positrons andelectrons producedas secondaries in thesources (e.g. SNR), inthe same regionwhere cosmic raysare being accelerated

They participate inthe accelerationprocess and turn outto have a very flatspectrum, which isresponsible, afterpropagation in theGalaxy, for theobserved positronexcess’


• Mechanism: the spinning B of the pulsar strips e- thataccelerated at the polar cap or at the outer gap emit γ thatmake production of e± that are trapped in the cloud,further accelerated and later released at τ ~ 105 years.

• Young (T < 105 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:Astrophysical Explanation:PulsarsPulsars



Are there “standard” astrophysical explanations ofthe PAMELA data?

Young, nearby pulsars

Not a new idea: Boulares, ApJ 342 (1989), Atoyan et al (1995)‏

Geminga pulsar




contribution of all nearby pulsars in the ATNF catalogue(∼150 pulsars) with d < 3 kpc with age 5 × 104 < T < 107 yr

D. Grasso et al. Astrop. Phys. 32 (2009), arXiv: 0905.0636v3


H. Yüksak et al., arXiv:0810.2784v2Contributions of e- & e+ fromGeminga assuming different distance,age and energetic of the pulsar diffuse mature &nearby young pulsars

Hooper, Blasi, and Serpico arXiv:0810.1527


ConclusionsConclusions PAMELA 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 deviationsfrom secondary production expectations.

High energy positron fraction (>10 GeV) increases significantly(and unexpectedly!) with energy. Primary source?Data at higher energies might help to resolve origin of rise(spillover limit ~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 anunprecedented statistical precision and is helping to improve the understanding of particle propagationin 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.



ThanksThanks

Documents

Bruno-sost Vulc 2010 01 - Laboratori Nazionali di Frascati · 2010-06-04 · •Geminga: 157 parsecs from Earth and 370,000 years old •B0656+14: 290 parsecs from Earth and 110,000