arXiv 0905.23182009-05hep-ph

具有保管保护的RS模型中Kaluza-Klein费米子对标准模型费米子耦合的影响

The Impact of Kaluza-Klein Fermions on Standard Model Fermion Couplings in a RS Model with Custodial Protection

Andrzej J. Buras, Bjoern Duling, Stefania Gori

备注：: 40 pages, 8 figures. Comments added, references added, typos corrected
发表信息：: JHEP 0909:076,2009
DOI：: 10.1088/1126-6708/2009/09/076

摘要：

我们重新考虑了重矢量类费米子对标准模型夸克与标准模型规范玻色子W和Z以及与标准模型希格斯玻色子玻色子H耦合的影响。将这些费米子在树的水平上积分，我们得到了可以在任何包含这种粒子的模型中使用的一般公式。我们应用这些公式的情况下，最轻的Kaluza-Klein（KK）费米子的Randall-Sundrum（RS）模型与保管保护的味道保存$Zd_L^i d_L^i$和味道违反$Zd_L^i d_L^j$耦合。我们指出，在这个模型中，还保护了$Zu_R^i u_R^i$和$Zu_R^i u_R^j$的耦合。特别地，我们明确地证明了这种保护不会被SM夸克与KK费米子的混合破坏，这是由潜在的P_LR对称性保证的。我们发现，KK费米子对Z耦合的影响虽然不可忽略，但明显小于Z与重KK规范玻色子Z_H和Z '的混合所产生的影响。W耦合的情况也是类似的，只有tb耦合例外，在tb耦合中，KK费米子的影响原则上大于规范玻色子混合所引起的影响。我们还明确地表明，在O（v^2/ M_{KK} ^2）处，放置在红外（IR）膜上的希格斯粒子的费米子-希格斯耦合不受KK贡献的影响，直到强手性抑制的贡献。CKM矩阵的校正，特别是其酉性的故障，被发现是小的。我们还研究了通过与KK-费米子混合产生的W的右手耦合，并引入了一个3 × 3矩阵，该矩阵描述了标准W的这些新相互作用中的味道违反模式。

英文摘要：

We reconsider the impact of heavy vector-like fermions on the couplings of standard model (SM) quarks to the SM gauge bosons W and Z and to the SM Higgs boson H. Integrating out these fermions at tree level we derive general formulae that can be used in any model containing such particles. We apply these formulae to the case of the lightest Kaluza-Klein (KK) fermions in a Randall-Sundrum (RS) model with a custodial protection of flavour conserving $Zd_L^i d_L^i$ and flavour violating $Zd_L^i d_L^j$ couplings. We point out that in this model also the couplings of $Zu_R^i u_R^i$ and $Zu_R^i u_R^j$ are protected. In particular we demonstrate explicitly that this protection is not spoiled by the mixing of the SM quarks with the KK fermions, which is guaranteed by the underlying P_LR symmetry. We find that the impact of KK fermions on the Z-couplings, while not negligible, is significantly smaller than the one coming from the mixing of Z with the heavy KK gauge bosons Z_H and Z'.The situation is similar for the W couplings with the only exception of the tb coupling where the impact of KK fermions can in principle be larger than the effects that are induced by gauge boson mixing. We also show explicitly that at O(v^2/M_{KK}^2) the fermion-Higgs couplings of a Higgs placed on the infrared (IR) brane is not affected by the KK contributions up to strongly chirally suppressed contributions. The corrections to the CKM matrix, in particular the breakdown of its unitarity, are found to be small. We also investigate the right-handed couplings of W that are generated through the mixing with KK-fermions and introduce a 3x3 matrix that describes the pattern of flavour violation in these new interactions of the standard W.

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英文摘要：

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