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arXiv 1005.4543hep-ph
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重费米子和对$b\rightarrow s+γ$的双圈电弱修正

Heavy fermions and two loop electroweak corrections to $b\rightarrow s+γ$

Xiu-Yi Yang, Tai-Fu Feng

摘要:

本文应用有效拉格朗日方法和壳层上方案,从某些特殊的双圈图中分析了稀有衰变$b\rightarrow s+γ$的电弱修正,在这些双圈图中,一个闭合的重费米子圈被附加到虚荷电规范玻色子或Higgs上。在退耦极限(内环虚费米子比电弱标度重得多)下,证明了当Higgs粒子与重费米子之间的相互作用不包含非退耦耦合时,最终结果满足退耦定理.采用新物理对相关耦合和质谱的普适假设,发现这两个环图对SM理论预测的$B\rightarrow X_{_s}γ$分支比的相对修正可以达到新物理$Λ_{_{\rm NP}}=200$ GeV能量标度的5%.

英文摘要:

Applying effective Lagrangian method and on-shell scheme, we analyze the electroweak corrections to the rare decay $b\rightarrow s+γ$ from some special two loop diagrams in which a closed heavy fermion loop is attached to the virtual charged gauge bosons or Higgs. At the decoupling limit where the virtual fermions in inner loop are much heavier than the electroweak scale, we verify the final results satisfying the decoupling theorem explicitly when the interactions among Higgs and heavy fermions do not contain the nondecoupling couplings. Adopting the universal assumptions on the relevant couplings and mass spectrum of new physics, we find that the relative corrections from those two loop diagrams to the SM theoretical prediction on the branching ratio of $B\rightarrow X_{_s}γ$ can reach 5% as the energy scale of new physics $Λ_{_{\rm NP}}=200$ GeV.

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