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arXiv 1702.07566astro-ph.HE
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电磁级联中的中微子产生:宇宙成因中微子的一个额外成分

Neutrino Production in Electromagnetic Cascades: An extra component of cosmogenic neutrino at ultrahigh energies

Kai Wang, Ruo-Yu Liu, Zhuo Li, Zi-Gao Dai

摘要:

超高能光子(UHE,$E \gtrsim 10^{18} \,\mathrm{eV}$)在星系际空间与低能宇宙背景辐射的湮灭过程中会产生μ子对,从而产生中微子。虽然μ子对产生的分支比很低,但其他通道的产物(主要是电子/正电子对)在随后的与宇宙背景辐射的相互作用中,可能会通过深Klein-Nishina区的康普顿散射将大部分能量转移到新产生的UHE光子中。这些新的UHE光子的再生然后提供了第二次机会来产生μ子对,增强中微子通量。我们研究了不同红移的UHE光子在星系际空间传播过程中的中微子产生,考虑了各种竞争过程,如UHE光子的对产生、双对产生以及UHE电子的三重态产生和同步辐射。把能量最小的出射粒子看作能量损失,得到了最先出射粒子的有效穿透长度,以及级联过程中的能量损失率和中微子发射率。最后,我们发现,由于产生的UHE光子和电子/正电子,UHE宇宙射线的传播会产生额外的UHE中微子分量。然而,这个分量的通量非常小,在没有强星系际磁场和强宇宙射电背景的情况下,在几个EeV处的通量最多只有传统宇宙成因中微子的$10\%$。额外成分的精确贡献取决于几个因素,例如,宇宙射电背景、星系际磁场、质子的光谱,这些都将在本文中讨论。

英文摘要:

Muon pairs can be produced in the annihilation of ultra-high energy (UHE, $E \gtrsim 10^{18} \,\mathrm{eV}$) photons with low energy cosmic background radiation in the intergalactic space, giving birth to neutrinos. Although the branching ratio of muon pair production is low, products of other channels, which are mainly electron/positron pairs, will probably transfer most of their energies into the new generated UHE photon in the subsequent interaction with the cosmic background radiation via Compton scattering in deep Klein-Nishina regime. The regeneration of these new UHE photons then provides a second chance to produce the muon pairs, enhancing the neutrino flux. We investigate the neutrino production in the propagation of UHE photons in the intergalactic space at different redshifts, considering various competing processes such as pair production, double pair production for UHE photons, and triplet production and synchrotron radiation for UHE electrons. Regarding the least energetic outgoing particles as energy loss, we obtain the effective penetration length of the leading particle, as well as energy loss rate including the neutrino emission rate in the cascade process. Finally, we find that an extra component of UHE neutrinos will arise from the propagation of UHE cosmic rays due to the generated UHE photons and electron/positrons. However, the flux of this component is quite small, with a flux of at most $10\%$ of that of the conventional cosmogenic neutrino at a few EeV, in the absence of a strong intergalactic magnetic field and a strong cosmic radio background. The precise contribution of extra component depends on several factors, e.g., cosmic radio background, intergalactic magnetic field, the spectrum of proton, which will be discussed in this work.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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