我们能从正电子通量“异常”中真正学到什么？
What can we really learn from positron flux 'anomalies'?
摘要：
我们提出了一个批判性的分析的观测约束，和理论建模，宇宙射线（CR）的产生和传播方面的银河系，这是相关的解释最近的正电子和反质子测量。我们给出了简单的，解析的，独立于模型的二次pbar通量的表达式，和二次e+通量的上限，通过忽略e+辐射损失，e+/（e+ + e-）<0.2 \pm 0.1到~300 GeV。这些表达式完全由刚性相关的克重，这是从稳定的CR秒高达~150 GeV/nuc，并在实验室中测量的核截面测量。pbar和e+的测量，可达~100 GeV，与这些估计是一致的，这意味着没有必要新的，非二次，pbar或e+源。e+通量的辐射损失抑制因子f_{s,e+}取决于e+在银河系中的传播，这在理论上是不理解的。一个粗略的，独立于模型的估计f_{s,e+} 1/3，可以得到在一个单一的能量，E \sim 20 GeV，从不稳定的二次衰变，并被发现是一致的e+测量，包括正电子分数PAMELA测量。我们表明，具体的详细模型，同意组成CR数据，同意我们的简单表达式的e+和pbar通量，并声称PAMELA测量的正电子分数需要新的主要e+源是基于假设，这是不支持的观测。如果PAMELA的结果是正确的，它们表明f_{s,e+}随能量略微增加，这为CR传播模型提供了一个有趣的约束。我们认为，测量的e+ pbar比更有用的挑战二次生产模型比正电子分数。
英文摘要：
We present a critical analysis of the observational constraints on, and of the theoretical modeling of, aspects of cosmic ray (CR) generation and propagation in the Galaxy, which are relevant for the interpretation of recent positron and anti-proton measurements. We give simple, analytic, model independent expressions for the secondary pbar flux, and an upper limit for the secondary e+ flux, obtained by neglecting e+ radiative losses, e+/(e+ + e-)<0.2\pm0.1 up to ~300 GeV. These expressions are completely determined by the rigidity dependent grammage, which is measured from stable CR secondaries up to ~150 GeV/nuc, and by nuclear cross sections measured in the laboratory. pbar and e+ measurements, available up to ~100 GeV, are consistent with these estimates, implying that there is no need for new, non-secondary, pbar or e+ sources. The radiative loss suppression factor f_{s,e+} of the e+ flux depends on the e+ propagation in the Galaxy, which is not understood theoretically. A rough, model independent estimate of f_{s,e+} 1/3 can be obtained at a single energy, E\sim20 GeV, from unstable secondary decay and is found to be consistent with e+ measurements, including the positron fraction measured by PAMELA. We show that specific detailed models, that agree with compositional CR data, agree with our simple expressions for the e+ and pbar flux, and that the claims that the positron fraction measured by PAMELA requires new primary e+ sources are based on assumptions, that are not supported by observations. If PAMELA results are correct, they suggest that f_{s,e+} is slightly increasing with energy, which provides an interesting constraint on CR propagation models. We argue that measurements of the e+ to pbar ratio are more useful for challenging secondary production models than the positron fraction.
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