* Astronomy

Title: Capability of the PAMELA Time-Of-Flight to identify light nuclei: results from a beam test calibration
Authors: D. Campana (1), R. Carbone (1 and 4), G. De Rosa (1), G. Osteria (1), S. Russo (2), W. Menn (3), V. Malvezzi (4), L. Marcelli (4), P. Picozza (4), R. Sparvoli (4), L. Bonechi (5), M. Bongi (6), S. Ricciarini (6), E. Vannuccini (6). ((1) INFN, Section of Naples, Naples (Italy), (2) Dept. of Physics, University of Naples and INFN, Naples (Italy), (3) Dept. of Physics, University of Siegen, Siegen (Germany), (4) Dept. of Physics, University of Rome Tor Vergata and INFN, Rome (Italy), (5) Dept. of Physics, University of Florence and INFN, Florence (Italy), (6) INFN, Section of Florence, Florence (Italy))

PAMELA is a space telescope orbiting around the Earth since June 2006. The scientific objectives addressed by the mission are the measurement of the antiprotons and positrons spectra in cosmic rays, the hunt for anti-nuclei as well as the determination of light nuclei fluxes from Hydrogen to Oxygen in a wide energy range and with very high statistics. In this paper the charge discrimination capabilities of the PAMELA Time-Of-Flight system for light nuclei, determined during a beam test calibration, will be presented.

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Title: Two dark matter components in N_{DM}MSSM and PAMELA data
Authors: Ji-Haeng Huh, Jihn E. Kim, Bumseok Kyae

We present the dark matter(DM) extension (by N_R) of the minimal supersymmetric standard model N_{DM}MSSM to give the recently reported high energy positron spectrum (10--50 GeV) of the PAMELA experiment. From the angular momentum consideration, one more DM component is introduced. The simplest possibility is to add two kinds of matter fields, N_R and E_R^c+E_R, and introduce the coupling e_R E_R^c N_R with an appropriate U(1)_R symmetry. This N_{DM}MSSM contains the discrete symmetry Z(6), and for some parameter ranges there result two DM components. For the MSSM fields, the conventional R-parity, which is a subgroup of Z(6), is preserved. We also present the needed parameter ranges of these additional particles.

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Title: New Positron Spectral Features from Supersymmetric Dark Matter - a Way to Explain the PAMELA Data?
Authors: Lars Bergstrom, Torsten Bringmann, Joakim Edsjo

The space-borne antimatter experiment PAMELA has recently reported a surprising rise in the positron to electron ratio at high energies. It has also recently been found that electromagnetic radiative corrections in some cases may boost the gamma-ray yield from supersymmetric dark matter annihilations in the galactic halo by up to three or four orders of magnitude, providing distinct spectral signatures for indirect dark matter searches to look for. Here, we investigate whether the same type of corrections can also lead to sizeable enhancements in the positron yield. We find that this is indeed the case, albeit for a smaller region of parameter space than for gamma rays; selecting models with a small mass difference between the neutralino and sleptons, like in the stau coannihilation region in mSUGRA, the effect becomes more pronounced. The resulting, rather hard positron spectrum with a relatively sharp cutoff may potentially fit the rising positron ratio measured by the PAMELA satellite. To do so, however, as seems also to be the case for most other dark matter models, very large "boost factors" have to be invoked that are not expected in current models of halo structure. If the predicted cutoff would also be confirmed by later PAMELA data or upcoming experiments, one could either assume non-thermal production in the early universe or non-standard halo formation to explain such a spectral feature as an effect of dark matter annihilation. At the end of the paper, we briefly comment on the impact of radiative corrections on other annihilation channels, in particular antiprotons and neutrinos.

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Title: Minimal Dark Matter predictions and the PAMELA positron excess
Authors: Marco Cirelli, Alessandro Strumia

We present Minimal Dark Matter and its univocal predictions for Dark Matter observables. During the idm2008 conference, PAMELA presented preliminary results showing an excess in the positron fraction: we find a good agreement, with a modest astrophysical boost factor.

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