Juan Zhang

PAMELA data and leptonically decaying dark matter

Recently PAMELA released their first results on the positron and antiproton ratios. Stimulated by the new data, we studied the cosmic ray propagation models and calculated the secondary positron and antiproton spectra. The low energy positron ratio can be consistent with data in the convection propagation model. Above similar to 10 GeV PAMELA data shows a clear excess on the positron ratio. However, the secondary antiproton is roughly consistent with the data. The positron excess may be evidence of dark matter annihilation or decay. We compare the positron and antiproton spectra with the data by assuming that dark matter annihilates or decays into different final states. The PAMELA data actually excludes quark pairs being the main final states, and disfavors gauge boson final states. Only in the case of leptonic final states can the positron and antiproton spectra be explained simultaneously. We also compare the decaying and annihilating dark matter scenarios which can account for the PAMELA results and find that the decaying dark matter is preferred. Finally, we consider a decaying neutralino dark matter model in the frame of supersymmetry with R-parity violation. The PAMELA data is well fitted with a neutralino mass of 600 similar to 2000 GeV and a lifetime of similar to 10(26) seconds. We also demonstrate that a neutralino with mass around 2 TeV can fit PAMELA and ATIC data simultaneously.

Discriminating different scenarios to account for the cosmic e ± excess by synchrotron and inverse Compton radiation

The excesses of the cosmic positron fraction recently measured by PAMELA and the electron spectra by ATIC, PPB-BETS, Fermi, and H.E.S.S. indicate the existence of primary electron and positron sources. The possible explanations include dark matter annihilation, decay, and astrophysical origin, like pulsars. In this work we show that these three scenarios can all explain the experimental results of the cosmic

Clumpiness enhancement of charged cosmic rays from dark matter annihilation with Sommerfeld effect

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Galactic Diffuse Gamma Rays—Recalculation Based on New Measurements of the Cosmic Electron Spectrum

excess. However, it may be difficult to discriminate these different scenarios by the local measurements of electrons and positrons. We propose possible discriminations among these scenarios through the synchrotron and inverse Compton radiation of the primary electrons/positrons from the region close to the Galactic center. Taking typical configurations, we find the three scenarios predict quite different spectra and skymaps of the synchrotron and inverse Compton radiation, though there are relatively large uncertainties. The most prominent differences come from the energy band

The diffuse Galactic γ-rays from dark matter annihilation

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Hard-scattering approach to strongly hindered magnetic-dipole transitions in quarkonium

for synchrotron emission and

Discriminating different scenarios to account for the PAMELA and ATIC data by synchrotron and IC radiation

ensuremath{gtrsim}10text{ }text{ }mathrm{GeV}

The diffuse Galactic ?-rays from dark matter annihilation

for inverse Compton emission. It might be able to discriminate at least the annihilating dark matter scenario from the other two given the high precision synchrotron and diffuse

C lum piness enhancem ent ofcharged cosm ic rays from dark m atter annihilation w ith Som m erfeld eect

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Discriminate different scenarios to account for the PAMELA and ATIC data by synchrotron and inverse Compton radiation

-ray skymaps in the future.