In the paper the authors from the Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences in Beijing proposed a new model trying to explain the knee at cosmic ray spectra.The knee kept as a puzzle in cosmic ray physics
The perspective of the detectability of Galactic dark matter subhaloes on the Fermi satellite is investigated in this work. Under the assumptions that dark matter annihilation accounts for the 'GeV excess' of the Galactic diffuse γ-rays discovered by EGRET and the γ-ray flux is dominated by the contribution from subhaloes of dark matter, we calculate the expected number of dark matter subhaloes that Fermi may detect. We show that Fermi may detect a few tens to several hundred subhaloes in a 1-year all-sky survey. Since EGRET observation is taken as a normalization, this prediction is independent of the particle physics property of dark matter. The uncertainties of the prediction are discussed in detail. We find that the major uncertainty comes from the mass function of subhaloes, i.e., whether the subhaloes are 'point like' (high-mass rich) or 'diffuse like' (low-mass rich). Other uncertainties like the background estimation and the observational errors will contribute a factor of 2—3.
In this paper,we discuss a possibility of studying properties of dark energy in long baseline neutrino oscillation experiments.We consider two types of models of neutrino dark energy.For one type of models the scalar field is taken to be quintessence-like and for the other phantom-like.In these models the scalar fields couple to the neutrinos to give rise to spatially varying neutrino masses.We will show that the two types of models predict different behaviors of the spatial variation of the neutrino masses inside the Earth and consequently result in different signals in long baseline neutrino oscillation experiments.
Monochromatic γ-rays are thought to be the smoking gun signal for identifying dark matter annihilation.However,the flux of monochromatic γ-rays is usually suppressed by virtual quantum effects since dark matter should be neutral and does not couple with γ-rays directly.In this work,we study the detection strategy of the monochromatic γ-rays in a future space-based detector.The flux of monochromatic γ-rays between 50 GeV and several TeV is calculated by assuming the supersymmetric neutralino as a typical dark matter candidate.The detection both by focusing on the Galactic center and in a scan mode that detects γ-rays from the whole Galactic halo are compared.The detector performance for the purpose of monochromatic γ-ray detection,with different energy and angular resolution,field of view,and background rejection efficiencies,is carefully studied with both analytical and fast Monte-Carlo methods.
In the LHC experiment, the H →γγ channel provides a clean final state with an effective mass peak that is reconstructed with great precision, despite the small branching ratio. As a consequence, the H →γγ channel is one of the most promising channels for the Higgs discovery in the very low mass region. In order to increase the sensitivity of the Higgs search, background rejection rate is very important, so γ/π 0 discrimination is one of the key points in the analysis. At least 40% of photons will convert with the experience of ATLAS and CMS. We constructed electromagnetic calorimeter (ECAL) in GEANT4 simulation, using 6 variables which have different shapes between converted γ and π 0 , with the TMVA (Toolkit for Multivariate Data Analysis) to do the separation. With this method we can get 30% to 60% π 0 rejection efficiency when keeping 90% converted γ efficiency, in the region of transverse momentum 15 GeV to 75 GeV, not only in MC sumulation but also in real data.
