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arXiv 2009.03315hep-ph
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稀有顶衰变PDMATHAAB和$t\to c g$中的$CP$不对称性

$CP$ asymmetries in the rare top decays $t\to cγ$ and $t\to c g$

Shyam Balaji

摘要:

几十年来,罕见的辐射变味顶衰变$t\to cγ$和$t\to cg$(以及更罕见的$t\to uγ$和$t\to ug$)一直是人们感兴趣的过程,因为它们为研究顶夸克性质提供了关键的探针。然而,一个明确的分析研究的分支比和$CP$不对称性所造成的这些循环水平的过程,迄今为止,逃避注意。在这项工作中,我们提供了配方的$CP$不对称造成的总动力学贡献的循环积分和虚部,以及更新的数值计算预测的标准模型(SM)分支分数。这些罕见的过程被抑制在SM的Glashow-Iliopoulos-Maiani(GIM)机制。然而,这里提出的结果可以很容易地导出用于SM的最小扩展,包括矢量夸克或在两希格斯双重模型中,辐射费米子衰变过程可以增强相对于SM的几个数量级。这样的过程为新的基础物理学提供了一个实验上干净的签名,并且可以通过当前的对撞机实验进行测试。这些主题超越SM理论是一个优雅的手段,提供改进的全球适合最新的结果出现的味道物理,CKM和精密电弱测量。

英文摘要:

The rare radiative flavour changing top decays $t\to cγ$ and $t\to cg$ (and the even rarer $t\to uγ$ and $t\to ug$) have been processes of interest for decades as they offer a key probe for studying top quark properties. However an explicit analytical study of the branching ratios and $CP$ asymmetries resulting from these loop level processes has thus far evaded attention. In this work, we provide the formulation for the $CP$ asymmetry resulting from the total kinetic contribution of the loop integrals and their imaginary parts, as well as an updated numerical computation of the predicted Standard Model (SM) branching fractions. These rare processes are suppressed in the SM by the Glashow-Iliopoulos-Maiani (GIM) mechanism. However, the results presented here can easily be exported for use in minimal extensions of the SM including vector-like quarks or in Two-Higgs-Doublet models where radiative fermionic decay processes can be enhanced relative to the SM by several orders of magnitude. Such processes provide an experimentally clean signature for new fundamental physics and can potentially be tested by current collider experiments. These topical beyond the SM theories are an elegant means to provide improved global fits to the latest results emerging from flavour physics, CKM and precision electroweak measurements.

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