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P A M E L A
Payload for Antimatter /
Matter Exploration and
Light-nuclei Astrophysics
Anticoincidence reduces out of
acceptance background
Sign of charge,
rigidity, dE/dx
Electron energy, dE/dx,
lepton-hadron
separation
e- p -
e+ p (He,...)
Trigger, ToF, dE/dx
- +
~470 kg
~360 W
~1.3
m
21.5 cm2sr
Resurs-DK1 satellite
Mass: 6.7 tonnes
Height: 7.4 m
Solar array area: 36 m2
• Main task: multi-spectral remote sensing of earth’s surface • Built by TsSKB Progress in Samara, Russia • Lifetime >3 years (assisted) • Data transmitted to ground via high-speed radio downlink • PAMELA mounted inside a pressurized container
Launch: 15th June 2006, 0800 UTC
• Quasi-polar (70.0°) • Elliptical (350 km - 600 km) • PAMELA traverses the South Atlantic Anomaly • At the South Pole PAMELA crosses the outer (electron) Van Allen belt
70.0o
610 km
350 km
SAA
Orbit characteristics
6.5 GV
interacting proton
candidate
PAMELA event
13 GV
Interacting helium nucleus
candidate
5.7 GV
non-interacting carbon nucleus
candidate
18 GV
non-interacting anti-proton
candidate
84 GV
interacting antiproton
candidate
92 GV positron
candidate
Antiprotons
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+ ~103-4)
Antiproton (NB: e-/p ~ 102)
Antiproton / positron identification
Antiproton Results
O. Adriani et al., PRL 102, 051101 (2009); PRL 105, 121101 (2010)
Donato et al. (PRL 102 (2009) 071301)
Simon et al. (ApJ 499 (1998) 250) Ptuskin et al. (ApJ 642 (2006) 902)
Cosmic-Ray Antiprotons and DM limits
D. G. Cerdeno, T. Delahaye & J. Lavalle, arXiv: 1108:1128 Antiproton flux predictions for a 12 GeV WIMP annihilating into different mass combinations of an intermediate two-boson state which further decays into quarks.
See also: •M. Asano, T. Bringmann & C. Weniger, arXiv:1112.5158. • M. Garny, A. Ibarra & S. Vogl, arXiv:1112.5155 • R. Kappl & M. W. Winkler, arXiv:1140.4376
PAMELA trapped antiprotons
Adriani et al., APJL 737 L29 (2011); arXiv:1107.4882
Positrons
Positron to Electron Fraction
Secondary production Moskalenko & Strong 98
Adriani et al, Astropart. Phys. 34 (2010) 1 arXiv:1001.3522 [astro-ph.HE]
But antiprotons in CRs are in agreement with secondary production
CR Positron spectrum significantly harder than expectations from secondary production
A Challenging Puzzle for CR Physics
Preliminary
Donato et al. (PRL 102 (2009) 071301)
Ptuskin et al. (ApJ 642 (2006) 902)
Simon et al. (ApJ 499 (1998) 250)
Preliminary
Astrophysical Explanation: SNR
P.Blasi et al., PRL 103 (2009) 051104 arXiv:0903.2794 [astro-ph]
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.
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
Astrophysical Explanation: Pulsars
Are there “standard” astrophysical explanations of the high energy positron data?
Young, nearby pulsars
Not a new idea: Boulares, ApJ 342 (1989), Atoyan et al (1995)
Geminga pulsar
Mechanism: the spinning B of the pulsar strips e- that accelerated at the polar cap or at the outer gap emit γ that make 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: Pulsars
Astrophysical Explanation: Pulsars
H. Yüksak et al., arXiv:0810.2784v2 Contributions of e- & e+ from Geminga assuming different distance, age and energetic of the pulsar diffuse mature &nearby young pulsars
Hooper, Blasi, and Serpico arXiv:0810.1527
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 dominant annihilation channel (possible candidate: Wino)
positrons antiprotons
Interpretation: DM Which DM spectra can fit the data? DM with and dominant annihilation channel (no “natural” SUSY candidate)
positrons antiprotons But B≈104
M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3
Interpretation: DM
DM with and dominant annihilation channel
positrons antiprotons
M. Cirelli et al., Nucl. Phys. B 813 (2009) 1; arXiv: 0809.2409v3
Interpretation: DM I. Cholis et al. Phys. Rev. D 80 (2009)
123518; arXiv:0811.3641v1
Electrons
Results from three ATIC flights
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 1+2+4 ATIC 1 ATIC 2 ATIC 4
FERMI All Electron Spectrum
A. Abdo et al., Phys.Rev.Lett. 102 (2009) 181101 M. Ackermann et al., Phys. Rev. D 82, 092004 (2010)
Electrons measured with H.E.S.S.
PAMELA electron (e-) spectrum
e+ + e-
e-
Flux=A • E-
= 3.18 ±0.05
O. Adriani et al., PRL 106 (2011) 201101.
Theoretical uncertainties on “standard” positron fraction
D. Grasso et al., arXiv:0905.0636
Does not fit at all the
PAMELA ratio:
Modify the injection indices of
GALPROP?
The Completed AMS Detector on ISS
The Completed AMS Detector on ISS
S. Schael, UCLA Dark Matter Conference 2012,