发表机构
University of Pittsburgh（匹兹堡大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究推导了含两个右手中微子的轻子生成中CP破坏上限的精确解析式，发现其低于文献结果，且倒置质量等级下比Davidson-Ibarra界限严格近两个数量级。
AI 中文摘要
我们提出了在最小I型跷跷板模型框架下、包含两个右手中微子（RHNs）的标准香草轻子生成情形中，CP破坏衰变不对称性上限的广义精确解析表达式，该表达式是层次极限下有效中微子质量的函数。我们通过对由成功轻子生成条件产生的四次方程根进行新颖的解析处理来推导该界限，其中CP不对称性、有效中微子质量及其他物理量作为参数出现。我们发现CP不对称性的上限是有效中微子质量的单调递增函数，在大有效质量区域渐近饱和至全局最大值。我们发现，我们得到的关于有效中微子质量的上限精确解析表达式小于文献中先前的解析结果。我们还发现，在大有效质量区域获得的、具有两个RHNs的CP不对称性全局最大值小于对应于具有三个RHNs的标准香草轻子生成情形的Davidson-Ibarra界限，从而导致对两个RHNs情形下最轻RHN质量产生更严格的约束，这与文献中先前的一些结果一致。我们发现，对于倒置中微子质量等级，与标准Davidson-Ibarra界限的偏差最为显著，接近两个数量级。
英文摘要
We present a generalized exact analytical expression for the upper bound on the CP-violating decay asymmetry in the case of standard vanilla leptogenesis within the minimal type-I seesaw with two Right Handed Neutrinos (RHNs) case scenario as a function of the effective neutrino mass in the hierarchical limit. We derive the bound using a novel analytical treatment of the roots of a quartic equation arising from the conditions for successful leptogenesis, in which the CP asymmetry, effective neutrino mass, and other physical quantities enter as parameters. We find that the upper bound on CP asymmetry is a monotonically increasing function of the effective neutrino mass, asymptotically saturating to a global maximum at the large effective mass regime. We find that our exact analytical expression of the upper bound as a function of the effective neutrino mass is smaller than the previous analytical results in the literature. We also find that the global maximum on CP asymmetry with two RHNs obtained at the large effective mass regime is less than the Davidson-Ibarra bound corresponding to the standard vanilla leptogenesis scenario with three RHNs, leading to a more stringent bound on the lightest RHN mass for the scenario with two RHNs, as expected from some previous results in literature. We find that the deviation from the standard Davidson-Ibarra bound becomes most dramatic for inverted neutrino mass hierarchy, by nearly two orders of magnitude.
Comments30 pages, 3 figures
