Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Comp...Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Compton scattering(ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.展开更多
Numerous simulations indicate that a large number of subhalos should be hosted by the Milky Way.The potential existence of a nearby subhalo could have important implications for our understanding of dark matter(DM)ann...Numerous simulations indicate that a large number of subhalos should be hosted by the Milky Way.The potential existence of a nearby subhalo could have important implications for our understanding of dark matter(DM)annihilation.In this study,we investigate the hypothetical presence of a nearby subhalo and set the upper limits on the DM annihilation cross section by analyzing the cosmic-ray antiproton spectrum.By presenting the ratios of annihilation cross section limits for scenarios with and without a nearby subhalo,we can quantitatively evaluate the potential impact of the nearby subhalo on the limits of the DM annihilation cross section.The impacts of the concentration model and the subhalo probability distribution have been considered.We explore the antiproton contribution of the potential nearby DM subhalo accounting for the DAMPE e+spectrum at~1.4 TeV and find that the current AMS-02 antiproton results do not limit this contribution.展开更多
The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,202...The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,2021.The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields,with a maximum fractional increase of 20%.The variations in trigger rates(increases or decreases)were found to be strongly dependent on the primary zenith angle.The flux of secondary particles increased significantly,following a trend similar to that of shower events.To better understand the observed behavior,Monte Carlo simulations were performed with CORSIKA and G4KM2A(a code based on GEANT4).We found that the experimental data(in saturated negative fields)were in good agreement with the simulations,assuming the presence of a uniform electric field of-700 V/cm with a thickness of 1500 m in the atmosphere above the observation level.Due to the acceleration/deceleration by the atmospheric electric field,the number of secondary particles with energy above the detector threshold was modified,resulting in the changes in shower detection rate.展开更多
基金Supported by the National Key Research and Development Program of China(Grant No.2016YFA0400203 and 2016YFA0400204)the National Natural Science Foundation of China(Grant Nos.11722328,U1738205,U1738203,11851303 and 11851305)the Program for Innovative Talents and Entrepreneur in Jiangsu。
文摘Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Compton scattering(ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.
基金Supported by the Science&Technology Development Fund of Tianjin Education Commission for Higher Education(2020KJ003)。
文摘Numerous simulations indicate that a large number of subhalos should be hosted by the Milky Way.The potential existence of a nearby subhalo could have important implications for our understanding of dark matter(DM)annihilation.In this study,we investigate the hypothetical presence of a nearby subhalo and set the upper limits on the DM annihilation cross section by analyzing the cosmic-ray antiproton spectrum.By presenting the ratios of annihilation cross section limits for scenarios with and without a nearby subhalo,we can quantitatively evaluate the potential impact of the nearby subhalo on the limits of the DM annihilation cross section.The impacts of the concentration model and the subhalo probability distribution have been considered.We explore the antiproton contribution of the potential nearby DM subhalo accounting for the DAMPE e+spectrum at~1.4 TeV and find that the current AMS-02 antiproton results do not limit this contribution.
基金Supported in China by National Key R&D program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203,2018YFA0404204)NSFC(U2031101,11475141,12147208)in Thailand by RTA6280002 from Thailand Science Research and Innovation。
文摘The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,2021.The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields,with a maximum fractional increase of 20%.The variations in trigger rates(increases or decreases)were found to be strongly dependent on the primary zenith angle.The flux of secondary particles increased significantly,following a trend similar to that of shower events.To better understand the observed behavior,Monte Carlo simulations were performed with CORSIKA and G4KM2A(a code based on GEANT4).We found that the experimental data(in saturated negative fields)were in good agreement with the simulations,assuming the presence of a uniform electric field of-700 V/cm with a thickness of 1500 m in the atmosphere above the observation level.Due to the acceleration/deceleration by the atmospheric electric field,the number of secondary particles with energy above the detector threshold was modified,resulting in the changes in shower detection rate.
