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arXiv 2503.10366hep-phastro-ph.COhep-th
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规范跷跷板中的热轻子生成是否依赖初始记忆？

Does thermal leptogenesis in a canonical seesaw rely on initial memory?

Partha Kumar Paul, Narendra Sahu, Shashwat Sharma

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10 pages, 9 captioned figures
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AI总结：

本文系统检验了I型跷跷板热轻子生成中仅最轻右手中微子贡献最终B-L不对称的传统假设，发现当较重右手中微子处于弱冲刷区域时会产生记忆效应，并刻画了该效应显著的参数空间。

摘要：

一个普遍观点认为，在具有传统层级结构右手中微子（RHN）的I型跷跷板场景中，热轻子生成过程里，最轻右手中微子（$N_1$）的CP破坏、非平衡衰变是$B-L$不对称的唯一相关来源。由较重右手中微子（$N_2$和$N_3$）产生的任何不对称都会被$N_1$所介导的轻子数破坏过程冲刷掉。本文全面检验了这一假设，同时考虑了衰变和逆衰变过程以及散射过程的贡献。我们发现，上述假设只有在所有右手中微子（$N_1$、$N_2$和$N_3$）都处于强冲刷区域时才成立。然而，我们发现，为了满足低能中微子振荡数据所给出的中微子质量和混合，至多只有一个右手中微子可以处于弱冲刷区域。这导致，如果$N_1$处于弱冲刷区域，则可以通过选择$N_2$和$N_3$的冲刷参数，使它们对最终$B-L$不对称的影响相对较小。另一方面，如果$N_2$或$N_3$处于弱冲刷区域，那么即使$N_1$处于强冲刷区域，它们所产生的不对称也可能影响最终的$B-L$不对称，我们称这种现象为记忆效应。我们刻画了记忆效应显著的参数空间。

英文摘要：

It is a common lore that in the thermal leptogenesis in the type-1 seesaw scenario with the conventional hierarchy of heavy right-handed neutrinos (RHNs), the CP violating, out-of-equilibrium decay of the lightest RHN ($N_1$) is the only relevant source of $B-L$ asymmetry. Any asymmetry produced by the heavier RHNs ($N_2$ and $N_3$) gets washed out by the lepton number violating processes mediated by $N_1$. In this paper, we examine this assumption comprehensively, considering decay and inverse decay processes as well as the inclusion of scatterings. We find that the above said assumption is true only if all the RHNs ($N_1, N_2$ and $N_3$) are in strong washout regime. However, we saw that, to satisfy the neutrino masses and mixing given by the low energy neutrino oscillation data, at most one of the RHNs can be in the weak washout regime. This leads to, if $N_1$ is in the weak washout regime, then the washout parameters of $N_2$ and $N_3$ can be chosen in such a way that the impact of $N_2$ and $N_3$ on the final $B-L$ asymmetry is relatively small. On the other hand, if $N_2$ or $N_3$ is in weak washout regime, then the asymmetry produced by them can affect the final $B-L$ asymmetry even if $N_1$ is in the strong washout regime, which we call the memory effect. We delineated the parameter space where the memory effect is significant.

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