Boron nuclei in cosmic rays(CRs)are believed to be mainly produced by the fragmentation of heavier nuclei,such as carbon and oxygen,via collisions with the interstellar matter.Therefore,the boron-tocarbon flux ratio(B...Boron nuclei in cosmic rays(CRs)are believed to be mainly produced by the fragmentation of heavier nuclei,such as carbon and oxygen,via collisions with the interstellar matter.Therefore,the boron-tocarbon flux ratio(B/C)and the boron-to-oxygen flux ratio(B/O)are very essential probes of the CR propagation.The energy dependence of the B/C ratio from previous balloon-borne and space-based experiments can be well described by a single power-law up to about 1 TeV/n within uncertainties.This work reports direct measurements of B/C and B/O in the energy range from 10 Ge V/n to 5.6 TeV/n with 6 years of data collected by the Dark Matter Particle Explorer,with high statistics and well controlled systematic uncertainties.The energy dependence of both the B/C and B/O ratios can be well fitted by a broken power-law model rather than a single power-law model,suggesting the existence in both flux ratios of a spectral hardening at about 100 Ge V/n.The significance of the break is about 5.6σand 6.9σfor the GEANT4 simulation,and 4.4σand 6.9σfor the alternative FLUKA simulation,for B/C and B/O,respectively.These results deviate from the predictions of conventional turbulence theories of the interstellar medium(ISM),which point toward a change of turbulence properties of the ISM at different scales or novel propagation effects of CRs,and should be properly incorporated in the indirect detection of dark matter via anti-matter particles.展开更多
基金funded by the Strategic Priority Science and Technology Projects in Space Science of Chinese Academy of Sciences(CAS)supported by the National Natural Science Foundation of China(11921003,11903084,12003076,12022503,12103094,and 12220101003)+7 种基金the Strategic Priority Science and Technology Projects of CAS(XDA15051100)the CAS Project for Young Scientists in Basic Research(YSBR-061)the Youth Innovation Promotion Association of CASthe Natural Science Foundation of Jiangsu Province(BK20201107)the Program for Innovative Talents and Entrepreneur in Jiangsusupported by the Swiss National Science Foundation(SNSF),Switzerlandthe National Institute for Nuclear Physics(INFN),Italythe European Research Council(ERC)under the European Unions Horizon 2020 research and innovation programme(851103)。
文摘Boron nuclei in cosmic rays(CRs)are believed to be mainly produced by the fragmentation of heavier nuclei,such as carbon and oxygen,via collisions with the interstellar matter.Therefore,the boron-tocarbon flux ratio(B/C)and the boron-to-oxygen flux ratio(B/O)are very essential probes of the CR propagation.The energy dependence of the B/C ratio from previous balloon-borne and space-based experiments can be well described by a single power-law up to about 1 TeV/n within uncertainties.This work reports direct measurements of B/C and B/O in the energy range from 10 Ge V/n to 5.6 TeV/n with 6 years of data collected by the Dark Matter Particle Explorer,with high statistics and well controlled systematic uncertainties.The energy dependence of both the B/C and B/O ratios can be well fitted by a broken power-law model rather than a single power-law model,suggesting the existence in both flux ratios of a spectral hardening at about 100 Ge V/n.The significance of the break is about 5.6σand 6.9σfor the GEANT4 simulation,and 4.4σand 6.9σfor the alternative FLUKA simulation,for B/C and B/O,respectively.These results deviate from the predictions of conventional turbulence theories of the interstellar medium(ISM),which point toward a change of turbulence properties of the ISM at different scales or novel propagation effects of CRs,and should be properly incorporated in the indirect detection of dark matter via anti-matter particles.
