在$B_s-\bar{B}_s$混合中的反常测量：CPT守恒和CPT破坏新物理学的作用
Reconciling anomalous measurements in $B_s-\bar{B}_s$ mixing: the role of CPT-conserving and CPT-violating new physics
摘要：
最近在$B_s \to J/ψϕ$衰变中观察到的反常现象和同号双μ子不对称性$A^b_{sl}$暗示了$\bsbsbar$混合中可能存在的新物理（NP）。我们用四个与模型无关的量来参数化NP：NP对有效哈密顿量的贡献的色散部分$M_{12}$和吸收部分$Γ_{12}$的幅度和相位。我们使用四个可观测量$ΔM_s$、$ΔΓ_s$、混合相位$β_s^{J/ψϕ}$和$A^b_{sl}$来约束这些参数。我们的定量拟合表明，NP应有助于显着的色散以及吸收的一部分。事实上，在超过99%的置信水平下，不贡献新吸收部分的模型是不受欢迎的。我们扩展了这种形式主义，包括CPT违反，并表明CPT违反本身，甚至在CPT守恒的新物理没有吸收部分的存在下，帮助只有轻微的同时解决这些异常。因此，NP吸收对$\bsbsbar$混合的贡献似乎是必不可少的，这意味着像$B_s \to τ^+ τ^-$这样的通道有很大的分支分数。
英文摘要：
Recently observed anomalies in the $B_s \to J/ψϕ$ decay and the like-sign dimuon asymmetry $A^b_{sl}$ hint at possible new physics (NP) in the $\bsbsbar$ mixing. We parameterize the NP with four model-independent quantities: the magnitudes and phases of the dispersive part $M_{12}$ and the absorptive part $Γ_{12}$ of the NP contribution to the effective Hamiltonian. We constrain these parameters using the four observables $ΔM_s$, $ΔΓ_s$, the mixing phase $β_s^{J/ψϕ}$, and $A^b_{sl}$. Our quantitative fit indicates that the NP should contribute a significant dispersive as well as absorptive part. In fact, models that do not contribute a new absorptive part are disfavored at more than 99% confidence level. We extend this formalism to include CPT violation, and show that CPT violation by itself, or even in presence of CPT-conserving new physics without an absorptive part, helps only marginally in the simultaneous resolution of these anomalies. The NP absorptive contribution to $\bsbsbar$ mixing therefore seems to be essential, and would imply a large branching fraction for channels like $B_s \to τ^+ τ^-$.
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