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 e ± 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 10 4 ∼ 10 9 MHz for synchrotron emission and 10 GeV 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 γ-ray skymaps in the future. PACS numbers: 95.35.+d,95.85.Ry,95.85.Pw,97.60.Gb

The Hard X-ray Modulation Telescope (HXMT) is a broad-band X-ray astronomical satellite from 1 to 250 keV. Understanding the X-ray background in detail will help to achieve a good performance of the instrument. In this work, we make use of the mass modeling technique to estimate the background of High Energy Telescope (HE) aboard HXMT. It consists of three steps. First, we built a complete geometric model of HXMT. Then based on the investigation about the space environment concerning HXMT low-earth orbit, in our simulation we considered cosmic rays, cosmic X-ray background (CXB), South Atlantic Anomaly (SAA) trapped particles, the albedo gamma, and neutrons from interaction of cosmic rays with the Earth's atmosphere. Finally, the Shielding Physics List supplied by Geant4 collaborations was adopted. According to our simulation, (1) the total background of HXMT/HE is about 540 count/s on average over 20-250 keV energy band after 100 days in orbit; (2) the delayed component caused by cosmic rays and SAA trapped particles dominates the full energy band of HXMT/HE; (3) some emission lines are prominent in the background continuum spectrum and will be used for inorbit calibration; (4) the estimated sensitivity is ∼0.1 mCrab at 50 keV with an exposure of 10 6 s.

We calculate the relativistic corrections of J/ψ, including electromagnetic corrections, to χ bJ → J/ψJ/ψ in the framework of nonrelativistic QCD factorization. The relativistic effect is found to increase the lower-order prediction for the decay width by about 10%, while the electromagnetism contribution is very small, about 0.2% for χ b0 and χ b2 . The total branching ratio is predicted to be of order 10 −5 for χ b0,b2 → J/ψJ/ψ, but 10 −11 for χ b1 → J/ψJ/ψ, since there is only electromagnetism contribution in this channel. We predict it is possible to observe these reactions in LHC. Finally, we estimate the decay width and branching ratio of χ cJ → ωω, φφ in the constituent quark model by our formula at the leading-order of relativistic correction and electromagnetic correction. The obtained branch ratio of χ c0,2 → φφ is in agreement with the experimental measurement in the order of magnitude.