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arXiv 1301.0914astro-ph.HEhep-ph
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河外宇宙射线及其特征

Extragalactic cosmic rays and their signatures

V. Berezinsky

摘要:

UHE质子在CMB中的传播特征是成对产生倾角和GZK截止。这些光谱特征的可见表现是微分光谱中的踝关节、GZK截止点和积分光谱中的E_{1/2}。在所有的实验中观察到的脚踝通常被解释为从银河到河外的宇宙射线的过渡。利用HiRes、望远镜阵列(TA)和俄歇探测器在能量(1-3)EeV下测量的质量组成,计算了银河系宇宙射线在这些能量下的各向异性,以及伸长曲线,我们强烈反对上面给出的脚踝解释。转变必须发生在较低的能量,最有可能在第二个膝盖的倾角模型预测。这个模型的另一个预测,倾角的形状,很好地证实了HiRes,TA,AGASA和雅库茨克探测器,并在能量重新校准后,由俄歇探测器。GZK临界值和E_{1/2}的预测开始与HiRes和TA数据一致。然而,直接测量的质量组成仍然是一个谜。虽然HiRes和TA探测器观察到质子占主导地位的质量组成,正如dip模型所要求的那样,俄歇探测器的数据有力地证明了核质量组成在能量高于4 EeV时稳定地变得更重,并在能量约35 EeV时达到铁。基于俄歇的方案与另一种解释一致,即能量为Ea =4 EeV的踝是从河外质子到河外核的跃迁。在较高能量下重核优势可以由质子的低能量加速E_{max} \sim 4 EeV和原子核的刚性依赖性E_{max} ^A =Z E_{max} $提供。最高能量的抑制可以解释为核破坏截止。

英文摘要:

The signatures of UHE proton propagation through CMB are pair-production dip and GZK cutoff. The visible manifestations of these spectral features are ankle, beginning of GZK cutoff in the differential spectrum and E_{1/2} in integral spectrum. Observed in all experiments, the ankle is usually interpreted as transition from galactic to extragalactic cosmic rays. Using the mass composition measured by HiRes, Telescope Array (TA) and Auger detectors at energy (1-3) EeV, calculated anisotropy of galactic cosmic rays at these energies, and the elongation curves we strongly argue against the interpretation of the ankle given above. The transition must occur at lower energy, most probably at the second knee as the dip model predicts. The other prediction of this model, the shape of the dip, is well confirmed by HiRes, TA, AGASA and Yakutsk detectors, and, after recalibration of energies, by Auger detector. Predicted beginning of GZK cutoff and E_{1/2} agree well with HiRes and TA data. However, directly measured mass composition remains a puzzle. While HiRes and TA detectors observe the proton-dominated mass composition, as required by the dip model, the data of Auger detector strongly evidence for nuclei mass composition becoming steadily heavier at energy higher than 4 EeV and reaching Iron at energy about 35 EeV. The Auger-based scenario is consistent with another interpretation of the ankle at energy E_a=4 EeV as transition from extragalactic protons to extragalactic nuclei. The heavy- nuclei dominance at higher energies may be provided by low-energy of acceleration for protons E_{max} \sim 4 EeV and rigidity-dependent E_{max}^A =Z E_{max}$ for nuclei. The highest energy suppression may be explained as nuclei-destroying cutoff.

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