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arXiv 2007.11725hep-ph
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引力纤体发生中的味效应

Flavour effects in gravitational leptogenesis

Rome Samanta, Satyabrata Datta

摘要:

在I型跷跷板机制中,引力背景中右手中微子的量子效应导致轻子和反轻子的不对称传播,从而导致Ricci标量和中微子Dirac-Yukawa耦合依赖的化学势,从而导致轻子的不对称平衡.在高温下,轻子数违反散射过程试图维持一个动态产生的轻子不对称平衡。然而,当温度下降时,相互作用变弱,不对称性消失。冻结的不对称性可以作为标准的Fukugita-Yanagida leptogenesis阶段($T_i\sim M_i$,其中$M_i$是$i$ th RH中微子的质量)之前预先存在的不对称性。因此,考虑重力稀薄生成对于给定的RH质谱的可行性是很自然的,这与衰变的成功稀薄生成是不一致的。这种引力诱导的轻子不对称性能够成功地再现所观察到的重子-光子比,其主要威胁是在$T_i\sim M_i$的轻子数违反洗出过程。在一个最小的跷跷板设置两个RH中微子,这些冲洗过程是强大到足以消除一个预先存在的不对称性的显着幅度。我们表明,当考虑到味道对冲洗过程的影响,该机制开辟了成功leptogenesis(重力)的质谱$M_2\gg 10^9 {\rm GeV}\gg M_1$与$M_1 \gtrsim 6.3 \times 10^6$ GeV的可能性。然后,我们简要地讨论了如何,在一般情况下,该机制留下了印记的低能量CP阶段和绝对轻中微子质量标度。

英文摘要:

Within the Type-I seesaw mechanism, quantum effects of the right-handed (RH) neutrinos in the gravitational background lead to an asymmetric propagation of lepton and anti-leptons which allows a Ricci scalar and neutrino Dirac-Yukawa coupling dependent chemical potential and therefore a lepton asymmetry in equilibrium. At high temperature, lepton number violating scattering processes try to maintain a dynamically generated lepton asymmetry in equilibrium. However, when the temperature drops down, the interactions become weaker, and the asymmetry freezes out. The frozen out asymmetry can act as a pre-existing asymmetry prior to the standard Fukugita-Yanagida leptogenesis phase ($T_i\sim M_i$, where $M_i$ is the mass of $i$th RH neutrino). It is then natural to consider the viability of gravitational leptogenesis for a given RH mass spectrum which is not consistent with successful leptogenesis from decays. Primary threat to this gravity-induced lepton asymmetry to be able to successfully reproduce the observed baryon-to-photon ratio is the lepton number violating washout processes at $T_i\sim M_i$. In a minimal seesaw set up with two RH neutrinos, these washout processes are strong enough to erase a pre-existing asymmetry of significant magnitude. We show that when effects of flavour on the washout processes are taken into account, the mechanism opens up the possibility of successful leptogenesis (gravitational) for a mass spectrum $M_2\gg 10^9 {\rm GeV}\gg M_1$ with $M_1 \gtrsim 6.3 \times 10^6$ GeV. We then briefly discuss how, in general, the mechanism leaves its imprints on the low energy CP phases and absolute light neutrino mass scale.

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