Electroweak baryogenesis from light fermion sources: A critical study
Electroweak baryogenesis from light fermion sources: A critical study
复制标题
光费米子源的电弱重子生成：一项关键研究
作者：
J. Cline;B. Laurent
电弱重子生成（EWBG）起源于希格斯玻色子与费米子（通常被认为是顶夸克）的非标准CP破坏相互作用，并被其大的汤川耦合增强。许多论文研究了由较轻费米子产生的EWBG，包括τ轻子和非对角夸克质量项。我们批判性地重新评估EWBG在这些情况下的可行性，比较预测的基础上的半经典（WKB）形式主义的源项的VEV插入近似（VIA），使用更新的碰撞项的值，并澄清弱sphaleron率的定义的差异。VIA系统地预言了一个重子不对称性，它比WKB形式主义大几个数量级。我们跟踪这两种形式主义的CP -违反源项的不同形状，表明在WKB源项的额外的空间导数导致大的取消时，它是集成在气泡壁轮廓。一个重要的例外是来自c-t夸克混合的源项，WKB预测也允许实际上大的重子不对称性。相比之下，类似的b-s混合源被发现是数量级太小。
Electroweak baryogenesis (EWBG) is sourced by nonstandard CP -violating interactions of the Higgs boson with fermions, usually taken to be the top quark, enhanced by its large Yukawa coupling. Numerous papers have studied EWBG sourced by lighter fermions, including the tau lepton and off-diagonal quark mass terms. We critically reassess the viability of EWBG in these scenarios, comparing the predictions based on the semiclassical (WKB) formalism for the source term to those from the VEV insertion approximation (VIA), using updated values for the collision terms, and clarifying discrepancies in the definition of the weak sphaleron rate. The VIA systematically predicts a baryon asymmetry that is orders of magnitude larger than the WKB formalism. We trace this to the differing shapes of the CP -violating source terms in the two formalisms, showing that the additional spatial derivative in the WKB source term causes large cancellations when it is integrated over the bubble wall profile. An important exception is a source term from c-t quark mixing, where the WKB prediction also allows for a realistically large baryon asymmetry. In contrast, the analogous b-s mixing source is found to be orders of magnitude too small.