用奥卡姆剃刀剖析cosmic-ray电子-正电子数据：已知脉冲星的作用
Dissecting cosmic-ray electron-positron data with Occam's Razor: the role of known Pulsars
摘要：
我们认为PAMELA测量的正电子分数和ATIC测量的总电子-正电子（e+e-）通量中报告的特殊光谱特征在附近的恒星产生的电子-正电子对中有一个非常自然的解释。虽然这种可能性很久以前就被指出，但当前数据质量的大幅提高可能会允许对问题进行反向工程：考虑到PAMELA和ATIC所青睐的脉冲星参数空间区域，是否存在已知的脉冲星可以解释这些数据合理的假设关于注入的e+e-对？在用于估计e+e-输出的简单基准模型的上下文中，我们考虑了所有已知的辐射源，如最完整的可用目录中所列。我们发现，这是不可能的，一个单一的脉冲星负责PAMELA e+分数异常和ATIC过剩，虽然两个单一的来源是在原则上足以解释这两个实验结果。PAMELA的过量e+可能来自一组成熟的恒星（年龄约10^6年），距离为0.8-1 kpc，或者来自一个单一的，更年轻和更近的来源，如Geminga。ATIC的数据需要更大的能量输出（也不太可能），并且倾向于与更强大、更遥远（1-2 kpc）和更年轻（年龄约10^5年）的恒星相关的起源。我们列出了几个候选人，可以单独或连贯地有助于解释PAMELA和ATIC数据。虽然一般抑制，我们发现，更远的贡献比1-2千秒差距可能有助于ATIC过剩的恒星。最后，我们强调费米-LAT在不久的将来将发挥多方面的决定性作用，（1）提供对e+e-通量的精确测量，（2）揭示尚未发现的中微子的存在，（3）寻找高能e+e-到达方向的各向异性。
英文摘要：
We argue that both the positron fraction measured by PAMELA and the peculiar spectral features reported in the total electron-positron (e+e-) flux measured by ATIC have a very natural explanation in electron-positron pairs produced by nearby pulsars. While this possibility was pointed out a long time ago, the greatly improved quality of current data potentially allow to reverse-engineer the problem: given the regions of pulsar parameter space favored by PAMELA and by ATIC, are there known pulsars that explain the data with reasonable assumptions on the injected e+e- pairs? In the context of simple benchmark models for estimating the e+e- output, we consider all known pulsars, as listed in the most complete available catalogue. We find that it is unlikely that a single pulsar be responsible for both the PAMELA e+ fraction anomaly and for the ATIC excess, although two single sources are in principle enough to explain both experimental results. The PAMELA excess e+ likely come from a set of mature pulsars (age ~ 10^6 yr), with a distance of 0.8-1 kpc, or from a single, younger and closer source like Geminga. The ATIC data require a larger (and less plausible) energy output, and favor an origin associated to powerful, more distant (1-2 kpc) and younger (age ~ 10^5$ yr) pulsars. We list several candidate pulsars that can individually or coherently contribute to explain the PAMELA and ATIC data. Although generally suppressed, we find that the contribution of pulsars more distant than 1-2 kpc could contribute for the ATIC excess. Finally, we stress the multi-faceted and decisive role that Fermi-LAT will play in the very near future by (1) providing an exquisite measurement of the e+e- flux, (2) unveiling the existence of as yet undetected pulsars, and (3) searching for anisotropies in the arrival direction of high-energy e+e-.
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