arXiv 1607.027972016-07-10astro-ph.COhep-ph

晚期带电电流弱相互作用对大爆炸核合成的惊人影响

The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis

E. Grohs, G. M. Fuller

备注：: 27 pages, 8 figures
DOI：: 10.1016/j.nuclphysb.2016.08.034

摘要：

早期宇宙中的弱相互作用带电电流过程（$ν_e+n\leftrightarrow p+e^-$，$\barν_e +p\leftrightarrow n+e^+$，$n\leftrightarrow p+e^-+\barν_e$）使中子和质子相互转换，对大爆炸核合成（BBN）轻元素丰度产额有重要影响，特别是对$^{4}{\rm He}$的影响。我们证明，这些过程的影响仍然是显着的，即使当他们运行远低于温度$T\sim0.7\,{\rm MeV}$通常调用“弱冻结”，实际上几乎到α粒子形成时代（$T \approx 0.1\,{\rm MeV}$）。这种物理现象在常用的BBN代码中被正确地捕捉到，尽管这种后期，低温持续的同位旋变化弱过程的影响，以及相关速率对轻子能量分布函数和阻塞因子的敏感性并没有得到广泛的重视。我们通过分析弱相互作用速率对中子寿命、轻子能量分布函数、熵、质子-中子质量差和哈勃膨胀率的依赖性来量化这种后期影响。我们在这里指出的效应使BBN成为任何超越标准模型的物理学的敏锐探测器，这些物理学改变了轻子数/能量分布，甚至微妙地改变了早期宇宙一直到$T=100\,{\rm keV}$附近的时代。

英文摘要：

The weak interaction charged current processes ($ν_e+n\leftrightarrow p+e^-$, $\barν_e +p\leftrightarrow n+e^+$, $n\leftrightarrow p+e^-+\barν_e$) interconvert neutrons and protons in the early universe and have significant influence on Big Bang Nucleosynthesis (BBN) light-element abundance yields, particulary that for $^{4}{\rm He}$. We demonstrate that the influence of these processes is still significant even when they operate well below temperatures $T\sim0.7\,{\rm MeV}$ usually invoked for "weak freeze-out," and in fact down nearly into the alpha-particle formation epoch ($T \approx 0.1\,{\rm MeV}$). This physics is correctly captured in commonly used BBN codes, though this late-time, low-temperature persistent effect of the isospin-changing weak processes, and the sensitivity of the associated rates to lepton energy distribution functions and blocking factors are not widely appreciated. We quantify this late-time influence by analyzing weak interaction rate dependence on the neutron lifetime, lepton energy distribution functions, entropy, the proton-neutron mass difference, and Hubble expansion rate. The effects we point out here render BBN a keen probe of any beyond-standard-model physics that alters lepton number/energy distributions, even subtly, in epochs of the early universe all the way down to near $T=100\,{\rm keV}$.

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