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arXiv 1902.06173astro-ph.HE
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理解cosmic ray正电子通量

Understanding the cosmic ray positron flux

Paolo Lipari

摘要:

阿尔法磁谱仪最近对宇宙线正电子通量的精确测量表明,当能量接近1 TeV时,谱线具有明显的软化特征。对这一结果的一种可能的解释是,观察到的特征测量了一种新的硬正电子源的最大能量,这种源可能与暗物质的自湮灭或衰变有关,或者与正电子加速器有关。以$E \simeq 25$ ~GeV为中心的正电子通量的逐渐硬化也可以被理解为跃迁的特征,其中由于二次产生,新的源超过了传统的组件。这种解释简单而有吸引力,但并非独一无二。另一种可能性,即正电子流完全是次级起源,仍然是可行的。在这种情况下,AMS观测到的正电子光谱软化是由能量损失效应产生的,在$e^-$光谱中也应该可以看到类似但不完全相同的结构。事实上,在电子中观察到了与正电子通量的硬化和软化类似的光谱特征,这需要一个一致的解释。精确测量的$e^+$和$e^-$光谱在TeV和多TeV的能量范围是至关重要的,以澄清这个问题。

英文摘要:

Recent precision measurements of the flux of cosmic ray positrons by the Alpha Magnetic Spectrometer show that the spectrum has a marked softening feature for energies close to one TeV. A possible interpretation of this result is that the observed feature measures the maximum energy of a new hard source of positrons perhaps associated to dark matter self--annihilation or decay, or to positron accelerators. A gradual hardening of the positron flux centered at $E \simeq 25$~GeV can also be understood as the signature of the transition where the new source overtakes the conventional component due to secondary production. This interpretation is simple and attractive, but it is not unique. The alternative possibility, that the positron flux is entirely of secondary origin, remains viable. In such a scenario the spectral softening observed by AMS for positrons is generated by energy loss effects, and a feature of similar, but not identical structure should be also visible in the $e^-$ spectrum. Spectral features similar to both the hardening and softening of the positron flux are in fact observed for electrons and call for a consistent explanation. Precision measurements of the $e^+$ and $e^-$ spectra in the TeV and multi--TeV energy range are crucial to clarify the problem.

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