论文标题
左右型号中的$ z b \ b $ b $顶点
The $Z b \bar b$ vertex in a left-right model
论文作者
论文摘要
我们考虑$ z b \ bar b $顶点的一环校正，以$ cp $ - 强度 - 左右型号（LRM），$ viz $。具有量规组$ su（2）_l \ times su（2）_r \ times u（1）$的型号。我们允许$ su（2）_l $和$ su（2）_r $的量规耦合常数不同。自发对称性断裂仅通过$ su（2）_l $和$ su（2）_r $的双重和/或单线完成。假定我们LRM的最轻的巨大中性仪表玻色子具有与标准型号（SM）的$ z $相同的Yukawa耦合；此假设的优势是，红外差异会自动从LRM中同一顶点的SM中的$ z b \ b $ b $顶点的减法中取消。我们对$ z b \ b $顶点进行适当的重新归一化，并明确检查其规格不变性和取消所有紫外线差异。我们发现，具有上述假设的LRM不能比SM的多higgs扩展$ z b $ b $顶点更好地适合$ z b \ b $ b $顶点。两种模型只有当一个人承认质量非常低的标量$ \ Lessim 50 $ GEV时，才能达到不错的拟合度。即使我们允许$ su（2）_l $和$ su（2）_r $的明显不同的量规耦合常数也是如此。
We consider the one-loop corrections to the $Z b \bar b$ vertex in a $CP$-conserving left--right model (LRM), $viz$. a model with gauge group $SU(2)_L \times SU(2)_R \times U(1)$. We allow the gauge coupling constants of $SU(2)_L$ and $SU(2)_R$ to be different. The spontaneous symmetry breaking is accomplished only by doublets and/or singlets of $SU(2)_L$ and $SU(2)_R$. The lightest massive neutral gauge boson of our LRM is assumed to have the same Yukawa couplings to bottom-quark pairs as the $Z$ of the Standard Model (SM); this assumption has the advantage that, then, the infrared divergences automatically cancel down in the subtraction of the $Z b \bar b$ vertex in the SM from the same vertex in the LRM. We effect a proper renormalization of the $Z b \bar b$ vertex and check explicitly both its gauge invariance and the cancellation of all the ultraviolet divergences. We find out that a LRM with the above assumptions cannot achieve a better fit to the $Z b \bar b$ vertex than a multi-Higgs extension of the SM, $viz$. both models can only achieve a decent fit when one admits scalar particles with very low masses $\lesssim 50$ GeV. This is true even when we allow for markedly different gauge coupling constants of $SU(2)_L$ and $SU(2)_R$.
