Dirac neutrinos and N eff . Part II. The freeze-in case
Dirac neutrinos and N eff . Part II. The freeze-in case
复制标题
狄拉克中微子和 N eff 。
DOI：
10.1088/1475-7516/2021/03/082
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发表时间：
2021
影响因子：
6.4
通讯作者：
Xu, Xun-Jie
中科院分区：
文献类型：
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作者：
Luo, Xuheng;Rodejohann, Werner;Xu, Xun-Jie
我们讨论狄拉克中微子，其右手分量 ν R 具有新的相互作用，可能会对相对论性中微子种类 N eff 的有效数量产生可测量的贡献。我们的目标是对各种可能性进行独立于模型的全面研究。包含自旋 0、自旋 1/2 或自旋 1 初始或最终状态的热物质衰变或散射的 ν R 生成过程。我们主要在冻结状态下以数值和分析方式计算 ν R 对 N eff 的贡献，因为之前已经研究了冻结状态。虽然我们的近似分析结果仅适用于冻结，但我们的数值计算也适用于冻结，包括两种状态之间的过渡。利用当前和未来对 N eff 的约束，我们获得了 CMB 实验对新相互作用的质量和耦合的限制和灵敏度。作为副产品，我们获得了希格斯-中微子相互作用的贡献，Δ N eff SM≃ 7.5× 10-12，假设中微子质量为 0.1 eV 并且由标准希格斯机制产生。
We discuss Dirac neutrinos whose right-handed component ν R has new interactions that may lead to a measurable contribution to the effective number of relativistic neutrino species N eff. We aim at a model-independent and comprehensive study on a variety of possibilities. Processes for ν R-genesis from decay or scattering of thermal species, with spin-0, spin-1/2, or spin-1 initial or final states are all covered. We calculate numerically and analytically the contribution of ν R to N eff primarily in the freeze-in regime, since the freeze-out regime has been studied before. While our approximate analytical results apply only to freeze-in, our numerical calculations work for freeze-out as well, including the transition between the two regimes. Using current and future constraints on N eff, we obtain limits and sensitivities of CMB experiments on masses and couplings of the new interactions. As a by-product, we obtain the contribution of Higgs-neutrino interactions, Δ N eff SM≃ 7.5× 10-12, assuming the neutrino mass is 0.1 eV and generated by the standard Higgs mechanism.