The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis
The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis
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晚带电电流弱相互作用对大爆炸核合成的惊人影响
DOI：
10.1016/j.nuclphysb.2016.08.034
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
G. Fuller
中科院分区：
文献类型：
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作者：
E. Grohs;G. Fuller
弱相互作用带电电流过程（ν e+ n p+ e-; ν ¥ e+ p n+ e+; n p+ e-+ ν ¥ e）在早期宇宙中相互转换中子和质子，对大爆炸核合成（BBN）轻元素丰度产生重大影响，特别是4 He的丰度。我们证明，即使这些过程的运行温度远低于通常称为“弱冻结”的温度T 0.7 MeV，并且实际上几乎进入了α粒子形成时期（T≈ 0.1 MeV），这些过程的影响仍然很大。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 keV附近的时代。
The weak interaction charged current processes (ν e+ n↔ p+ e−; ν¯ e+ p↔ n+ e+; n↔ p+ e−+ ν¯ e) interconvert neutrons and protons in the early universe and have significant influence on Big Bang Nucleosynthesis (BBN) light-element abundance yields, particularly that for 4 He. We demonstrate that the influence of these processes is still significant even when they operate well below temperatures T∼ 0.7 MeV usually invoked for “weak freeze-out,” and in fact down nearly into the alpha-particle formation epoch (T≈ 0.1 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 keV.