Adriani O, Akaike Y, Asano K, Asaoka Y, Berti E, Bigongiari G, Binns W R, Bongi M, Brogi P, Bruno A, Buckley J H, Cannady N, Castellini G, Checchia C, Cherry M L, Collazuol G, de Nolfo G A, Ebisawa K, Ficklin A W, Fuke H, Gonzi S, Guzik T G, Hams T, Hibino K, Ichimura M, Ioka K, Ishizaki W, Israel M H, Kasahara K, Kataoka J, Kataoka R, Katayose Y, Kato C, Kawanaka N, Kawakubo Y, Kobayashi K, Kohri K, Krawczynski H S, Krizmanic J F, Maestro P, Marrocchesi P S, Messineo A M, Mitchell J W, Miyake S, Moiseev A A, Mori M, Mori N, Motz H M, Munakata K, Nakahira S, Nishimura J, Okuno S, Ormes J F, Ozawa S, Pacini L, Papini P, Rauch B F, Ricciarini S B, Sakai K, Sakamoto T, Sasaki M, Shimizu Y, Shiomi A, Spillantini P, Stolzi F, Sugita S, Sulaj A, Takita M, Tamura T, Terasawa T, Torii S, Tsunesada Y, Uchihori Y, Vannuccini E, Wefel J P, Yamaoka K, Yanagita S, Yoshida A, Yoshida K, Zober W V
Department of Physics Department of Physics, University of Florence, Via Sansone, 1-50019, Sesto Fiorentino, Italy.
INFN Sezione di Florence, Via Sansone, 1-50019, Sesto Fiorentino, Italy.
Phys Rev Lett. 2022 Dec 16;129(25):251103. doi: 10.1103/PhysRevLett.129.251103.
We present the measurement of the energy dependence of the boron flux in cosmic rays and its ratio to the carbon flux in an energy interval from 8.4 GeV/n to 3.8 TeV/n based on the data collected by the Calorimetric Electron Telescope (CALET) during ∼6.4 yr of operation on the International Space Station. An update of the energy spectrum of carbon is also presented with an increase in statistics over our previous measurement. The observed boron flux shows a spectral hardening at the same transition energy E_{0}∼200 GeV/n of the C spectrum, though B and C fluxes have different energy dependences. The spectral index of the B spectrum is found to be γ=-3.047±0.024 in the interval 25<E<200 GeV/n. The B spectrum hardens by Δγ_{B}=0.25±0.12, while the best fit value for the spectral variation of C is Δγ_{C}=0.19±0.03. The B/C flux ratio is compatible with a hardening of 0.09±0.05, though a single power-law energy dependence cannot be ruled out given the current statistical uncertainties. A break in the B/C ratio energy dependence would support the recent AMS-02 observations that secondary cosmic rays exhibit a stronger hardening than primary ones. We also perform a fit to the B/C ratio with a leaky-box model of the cosmic-ray propagation in the Galaxy in order to probe a possible residual value λ_{0} of the mean escape path length λ at high energy. We find that our B/C data are compatible with a nonzero value of λ_{0}, which can be interpreted as the column density of matter that cosmic rays cross within the acceleration region.
我们基于量热电子望远镜（CALET）在国际空间站上约6.4年运行期间收集的数据，给出了宇宙射线中硼通量的能量依赖性及其在8.4 GeV/n至3.8 TeV/n能量区间与碳通量之比的测量结果。还给出了碳能谱的更新结果，其统计量比我们之前测量时有所增加。尽管硼和碳通量具有不同的能量依赖性，但观测到的硼通量在碳谱相同的转变能量(E_{0}\sim200)GeV/n处出现谱硬化。发现硼谱在25<E<200 GeV/n区间的谱指数为γ = -3.047±0.024。硼谱硬化了Δγ(_B)=0.25±0.12，而碳谱变化的最佳拟合值为Δγ(_C)=0.19±0.03。硼/碳通量比与0.09±0.05的硬化相符，不过鉴于当前的统计不确定性，不能排除单一幂律能量依赖性。硼/碳比能量依赖性的突变将支持最近阿尔法磁谱仪（AMS - 02）的观测结果，即次级宇宙射线比初级宇宙射线表现出更强的硬化。我们还用银河系中宇宙射线传播的泄漏箱模型对硼/碳比进行拟合，以探测高能下平均逃逸路径长度λ的可能残余值λ(_0)。我们发现我们的硼/碳数据与非零值的λ(_0)相符，这可以解释为宇宙射线在加速区域内穿过的物质柱密度。
