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arXiv 0712.2008hep-ph
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CP -违反$WWγ$顶点诱导的费米子电偶极矩的有效拉格朗日方法

Effective Lagrangian approach to fermion electric dipole moments induced by a CP--violating $WWγ$ vertex

H. Novales--Sanchez, J. J. Toscano

备注：
14 pages and 2 figures
发表信息：
Phys.Rev.D77:015011,2008
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摘要：

本文用量纲正则化方法计算了$WWγ$顶点的两个CP-破坏分量$ \tildeκ_γW^+_μW^-_ν\tilde{F}^{μν}$和$(\tildeλ_γ/ m^2_W)W^+_{μν}W^{-ν}_{\ ρ}\tilde{F}^{ρμ}$对费米子电偶极矩的单圈贡献，并根据退耦定理重新考察了它在低能时的影响.通过采用$SU_L(2)\times U_Y(1)$ -不变方法导出了这些耦合所满足的Ward恒等式，并讨论了它们在辐射修正中的意义。本文重复了以前关于$\tildeκ_γ$的结果，并将其边界更新为$|\tildeκ_γ| <5.2\times 10^{-5}$，但发现与已有的关于$\tildeλ_γ$的结果不一致，特别是从中子EDM的极限中找到了$|\tildeλ_γ|<1.9\times10^{-2}$的上界，比以前的结果降低了2个数量级以上.有人认为，$\tildeκ_γ$和$\tildeλ_γ$界限之间的这种差异是一个可以预期的根据解耦定理。这个论点是加强仔细分析低能量行为的循环功能。上界的$W$ EDM，$|d_W|<6.2\times 10^{-21} e\cdot cm$，和磁四极矩，$|\tilde{Q}_W|<3\times 10^{-36} e\cdot cm^2$，推导。估计了第二族和第三族夸克和带电轻子的EDM。特别地，对于$t$和$b$夸克，分别发现了与$ 10^{-20} e\cdot cm$和$10^{-21} e\cdot cm$一样大的EDM。

英文摘要：

The one--loop contribution of the two CP--violating components of the $WWγ$ vertex, $ \tildeκ_γW^+_μW^-_ν\tilde{F}^{μν}$ and $(\tildeλ_γ/ m^2_W)W^+_{μν}W^{-ν}_{\ ρ}\tilde{F}^{ρμ}$, on the electric dipole moment (EDM) of fermions is calculated using dimensional regularization and its impact at low energies reexamined in the light of the decoupling theorem. The Ward identities satisfied by these couplings are derived by adopting a $SU_L(2)\times U_Y(1)$--invariant approach and their implications in radiative corrections discussed. Previous results on $\tildeκ_γ$, whose bound is updated to $|\tildeκ_γ| <5.2\times 10^{-5}$, are reproduced, but disagreement with those existing for $\tildeλ_γ$ is found. In particular, the upper bound $|\tildeλ_γ|<1.9\times10^{-2}$ is found from the limit on the neutron EDM, which is more than 2 orders of magnitude less stringent than that of previous results. It is argued that this difference between the $\tildeκ_γ$ and $\tildeλ_γ$ bounds is the one that might be expected in accordance with the decoupling theorem. This argument is reinforced by analyzing careful the low--energy behavior of the loop functions. The upper bounds on the $W$ EDM, $|d_W|<6.2\times 10^{-21} e\cdot cm$, and the magnetic quadrupole moment, $|\tilde{Q}_W|<3\times 10^{-36} e\cdot cm^2$, are derived. The EDM of the second and third families of quarks and charged leptons are estimated. In particular, EDM as large as $ 10^{-20} e\cdot cm$ and $10^{-21} e\cdot cm$ are found for the $t$ and $b$ quarks, respectively.

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