Recent observations show that the spectra of cosmic ray nuclei start to harden above ～ 102 GeV, which contradicts the conventional steady-state cosmic ray model. We had suggested that this anomaly is due to the propa...Recent observations show that the spectra of cosmic ray nuclei start to harden above ～ 102 GeV, which contradicts the conventional steady-state cosmic ray model. We had suggested that this anomaly is due to the propagation effect of cosmic rays released from local young cosmic ray sources; the total flux of cosmic rays should be computed with the Myriad Model, where a contribution from sources in the local catalog is added to the background. However, although the hardening could be elegantly explained in this model, the model parameters obtained from the fit are skewed toward a region with fast diffusion and a low supernova rate in the Galaxy, in disagreement with other observations. We further explore this model in order to set up a concordant picture. Two possible improvements related to cosmic ray sources are considered. First, instead of the usual axisymmetric disk model, we examine a spiral model for the source distribution. Second, for nearby and young sources which are necessary to explain the hardening, we allow for an energy-dependent escape. We find that a major improvement comes from incorporating an energy-dependent escape time for local sources, and with both modifications not only are the cosmic ray proton and helium anomalies resolved, but also the parameters attain values in a reasonable range compatible with other analyses.展开更多
In order to reveal the nature of dark matter,it is crucial to detect its non-gravitational interactions with the standard model particles.The traditional dark matter searches focused on the so-called weakly interactin...In order to reveal the nature of dark matter,it is crucial to detect its non-gravitational interactions with the standard model particles.The traditional dark matter searches focused on the so-called weakly interacting massive particles.However,this paradigm is strongly constrained by the null results of current experiments with high precision.Therefore there is a renewed interest of searches for heavy dark matter particles above TeV scale.The Large High Altitude Air Shower Observatory(LHAASO)with large effective area and strong background rejection power is very suitable to investigate the gamma-ray signals induced by dark matter annihilation or decay above TeV scale.In this document,we review the theoretical motivations and background of heavy dark matter.We review the prospects of searching for the gamma-ray signals resulted from dark matter in the dwarf spheroidal satellites and Galactic halo for LHAASO,and present the projected sensitivities.We also review the prospects of searching for the axion-like particles,which are a kind of well motivated light pseudo-scalars,through the LHAASO measurement of the very high energy gamma-ray spectra of astrophysical sources.展开更多
基金Supported by the National Natural Science Foundation of China
文摘Recent observations show that the spectra of cosmic ray nuclei start to harden above ～ 102 GeV, which contradicts the conventional steady-state cosmic ray model. We had suggested that this anomaly is due to the propagation effect of cosmic rays released from local young cosmic ray sources; the total flux of cosmic rays should be computed with the Myriad Model, where a contribution from sources in the local catalog is added to the background. However, although the hardening could be elegantly explained in this model, the model parameters obtained from the fit are skewed toward a region with fast diffusion and a low supernova rate in the Galaxy, in disagreement with other observations. We further explore this model in order to set up a concordant picture. Two possible improvements related to cosmic ray sources are considered. First, instead of the usual axisymmetric disk model, we examine a spiral model for the source distribution. Second, for nearby and young sources which are necessary to explain the hardening, we allow for an energy-dependent escape. We find that a major improvement comes from incorporating an energy-dependent escape time for local sources, and with both modifications not only are the cosmic ray proton and helium anomalies resolved, but also the parameters attain values in a reasonable range compatible with other analyses.
文摘In order to reveal the nature of dark matter,it is crucial to detect its non-gravitational interactions with the standard model particles.The traditional dark matter searches focused on the so-called weakly interacting massive particles.However,this paradigm is strongly constrained by the null results of current experiments with high precision.Therefore there is a renewed interest of searches for heavy dark matter particles above TeV scale.The Large High Altitude Air Shower Observatory(LHAASO)with large effective area and strong background rejection power is very suitable to investigate the gamma-ray signals induced by dark matter annihilation or decay above TeV scale.In this document,we review the theoretical motivations and background of heavy dark matter.We review the prospects of searching for the gamma-ray signals resulted from dark matter in the dwarf spheroidal satellites and Galactic halo for LHAASO,and present the projected sensitivities.We also review the prospects of searching for the axion-like particles,which are a kind of well motivated light pseudo-scalars,through the LHAASO measurement of the very high energy gamma-ray spectra of astrophysical sources.
