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arXiv 0907.2754hep-ph
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SU(3)_c X SU(4)_L X U(1)_x模型中夸克族非普适性效应

Effects of quark family nonuniversality in SU(3)_c X SU(4)_L X U(1)_x models

Jorge L. Nisperuza, Luis A. Sanchez

摘要:

在标准模型的$SU(3)_c\otimes SU(4)_L\otimes U(1)_X$扩展中出现了变味中性流,因为费米子族之间的反常抵消需要一代夸克在规范群下与另外两代夸克不同地变换。在弱基中,夸克族之间的区别是没有意义的。然而,在质量本征态基础上,Cabibbo-Kobayashi-Maskawa混合矩阵激励我们将左手夸克分类到族中。在这个意义上,原则上有三种不同的夸克弱本征态到质量本征态的分配。在本工作中,我们利用Z极的测量、原子宇称破缺数据和中性介子混合的实验输入,研究了两个基于3-4-1对称性的不含奇异电荷的不同模型,和解决夸克家族的非普适性的影响,对边界的混合角之间的两个中性电流的模型和质量尺度$M_{Z_2}$和$M_{Z_3}$的新的理论预言的中性规范玻色子。最重的夸克族必须进行不同的变换,以保持$M_{Z_2}$和$M_{Z_3}$的下限尽可能低,而不违反实验约束。

英文摘要:

Flavour changing neutral currents arise in the $SU(3)_c\otimes SU(4)_L\otimes U(1)_X$ extension of the standard model because anomaly cancellation among the fermion families requires one generation of quarks to transform differently from the other two under the gauge group. In the weak basis the distinction between quark families is meaningless. However, in the mass eigenstates basis, the Cabibbo-Kobayashi-Maskawa mixing matrix motivates us to classify left-handed quarks in families. In this sense there are, in principle, three different assignments of quark weak eigenstates into mass eigenstates. In this work, by using measurements at the Z-pole, atomic parity violation data and experimental input from neutral meson mixing, we examine two different models without exotic electric charges based on the 3-4-1 symmetry, and address the effects of quark family nonuniversality on the bounds on the mixing angle between two of the neutral currents present in the models and on the mass scales $M_{Z_2}$ and $M_{Z_3}$ of the new neutral gauge bosons predicted by the theory. The heaviest family of quarks must transform differently in order to keep lower bounds on $M_{Z_2}$ and $M_{Z_3}$ as low as possible without violating experimental constraints.

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