论文标题
与新粒子物种重新访问大爆炸核合成：与核子共渗的效果
Revisiting big bang nucleosynthesis with a new particle species : effect of co-annihilation with nucleons
论文作者
论文摘要
在大爆炸核合成（BBN）中，光质丰度由中子到普罗顿（$ n/p $）的比例决定，该比由早期宇宙中的标准弱过程控制。在这里，我们研究了一个额外的粒子物种（$χ$）的效果，该物种\ textit {co-nihihilates}与中子（质子），从而在以前的过程中可能更改（$ n/p $）的比率。我们发现在决定（$ n/p $）比率和$χ$的收益率时，共同宣布与弱相互作用之间存在一个新颖的相互作用。与弱耦合（$ g_f $）相比，大型共辐射强度（$ g_d $）可能会改变热浴中的核子数量，从而从其标准演变中修改（$ n/p $）的比率。我们发现，以$ g_d/g_f \ Lessim 10^{ - 2} $恢复标准BBN预测，而$χ$的质量比中子质量小得多。当$χ$的质量与中子质量相媲美时，我们可以允许大$ g_d/g_f〜（\ gtrsim 10^2）$值，因为$χ$的热丰度变为Boltzmann支持。因此，（$ n/p $）的比率通过后期时期的主要弱过程恢复到其标准值。我们还讨论了新粒子在共同灭绝的有效theroy框架中的稳定性。此外，共同浸泡相互作用在近代领先的顺序下会产生$χ$和核子的弹性散射。这提供了一种在直接检测实验中探测场景的方法，如果$χ$在宇宙学的时间范围内意外稳定。
In big bang nucleosynthesis (BBN), the light matter abundance is dictated by the neutron-to-proton ($n/p$) ratio which is controlled by the standard weak processes in the early universe. Here, we study the effect of an extra particle species ($χ$) which \textit{co-annihilates} with neutron (proton), thereby potentially changing the ($n/p$) ratio in addition to the former processes. We find a novel interplay between the co-annihilation and the weak interaction in deciding the ($n/p$) ratio and the yield of $χ$. Large co-annihilation strength ($G_D$) in comparison to the weak coupling ($G_F$), potentially can alter the number of nucleons in the thermal bath modifying the ($n/p$) ratio from its standard evolution. We find that the standard BBN prediction is restored for $G_D/G_F \lesssim 10^{-2}$, while the mass of $χ$ being much smaller than the neutron mass. When the mass of $χ$ is comparable to the neutron mass, we can allow large $G_D/G_F ~(\gtrsim 10^2)$ values, as the thermal abundance of $χ$ becomes Boltzmann-suppressed. Therefore, the ($n/p$) ratio is restored to its standard value via dominant weak processes in later epochs. We also discuss the stability of the new particle in an effective theroy framework for co-annihilation. Further, the co-annihilation interaction generates elastic scattering of $χ$ and nucleons at the next-to-leading order. This provides a way to probe the scenario in direct detection experiments, if $χ$ is accidentally stable over cosmological timescale.
