Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), E-28040 Madrid, Spain.
I. Physics Institute and JARA-FAME, RWTH Aachen University, D-52056 Aachen, Germany.
Phys Rev Lett. 2018 Aug 3;121(5):051103. doi: 10.1103/PhysRevLett.121.051103.
A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on 2.2×10^{6} events is presented. The detailed rigidity dependence of the nitrogen flux spectral index is presented for the first time. The spectral index rapidly hardens at high rigidities and becomes identical to the spectral indices of primary He, C, and O cosmic rays above ∼700 GV. We observed that the nitrogen flux Φ_{N} can be presented as the sum of its primary component Φ_{N}^{P} and secondary component Φ_{N}^{S}, Φ_{N}=Φ_{N}^{P}+Φ_{N}^{S}, and we found Φ_{N} is well described by the weighted sum of the oxygen flux Φ_{O} (primary cosmic rays) and the boron flux Φ_{B} (secondary cosmic rays), with Φ_{N}^{P}=(0.090±0.002)×Φ_{O} and Φ_{N}^{S}=(0.62±0.02)×Φ_{B} over the entire rigidity range. This corresponds to a change of the contribution of the secondary cosmic ray component in the nitrogen flux from 70% at a few GV to <30% above 1 TV.
基于 2.2×10^{6}个事件，我们对 2.2~3.3 TV 的氮流的精确测量（每单位电荷的动量）。首次呈现了氮流能谱指数随磁刚度的详细依赖性。在高磁刚度下，谱指数迅速变硬，与≥700 GV 的初级氦、碳和氧宇宙射线的谱指数相同。我们观察到氮流 Φ_{N}可以表示为其初级成分 Φ_{N}^{P}和次级成分 Φ_{N}^{S}的和，即 Φ_{N}=Φ_{N}^{P}+Φ_{N}^{S}，我们发现 Φ_{N}可以很好地由氧通量 Φ_{O}（初级宇宙射线）和硼通量 Φ_{B}（次级宇宙射线）的加权和来描述，在整个磁刚度范围内，Φ_{N}^{P}=(0.090±0.002)×Φ_{O}和 Φ_{N}^{S}=(0.62±0.02)×Φ_{B}。这对应于在几 GV 时次级宇宙射线成分对氮流的贡献从 70%变化到>1 TV 时的<30%。
