Detection of spectral hardenings in cosmic-ray boron-to-carbon and boron-to-oxygen flux ratios with DAMPE  

“悟空”号卫星探测到宇宙线硼/碳和硼/氧流量比例的能谱拐折结构

作　　者：无 

机构地区：[1]DAMPE Collaboration

出　　处：《Science Bulletin》2022年第21期2162-2166,共5页科学通报（英文版）

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);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 CAS;the Natural Science Foundation of Jiangsu Province(BK20201107);the Program for Innovative Talents and Entrepreneur in Jiangsu;supported by the Swiss National Science Foundation(SNSF),Switzerland;the National Institute for Nuclear Physics(INFN),Italy;the European Research Council(ERC)under the European Unions Horizon 2020 research and innovation programme(851103)。

摘　　要：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.宇宙线中的硼核主要是碳核、氧核等在传播过程中和星际物质发生碰撞后产生的次级粒子,因此硼/碳流量比和硼/氧流量比可以用以研究宇宙线在传播路径上的相互作用过程.根据以往高空气球实验和空间实验的测量结果,在1 TeV/n以下能区,硼/碳比随能量的变化在测量误差范围内符合单一幂律下降的分布.基于“悟空”号卫星前6年的观测数据,合作组获得了10 Ge V/n~5.6 TeV/n能区宇宙线硼/碳比和硼/氧比的直接测量结果,发现硼/碳比和硼/氧比随能量的变化在整个观测能区显著偏离单一幂律分布,两者在相同的能量处(约100 GeV)出现能谱变平的拐折结构.基于GEANT4强子作用模型给出的结果,拐折结构的置信度对硼/碳比和硼/氧比分别达到5.6σ和6.9σ;而基于Fluka强子作用模型给出的结果,该结构的置信度分别达到4.4σ和6.9σ.该观测结果显著偏离经典星际介质湍流理论给出的预测,表明传统宇宙线传播模型需要修改,也意味着基于反物质宇宙线的暗物质间接探测的天体物理背景需要重新估计.

关 键 词：DAMPE Commic-ray CR propagation B/C ratio B/O ratio 

分 类 号：V474[航空宇航科学与技术—飞行器设计]