Reconciling anomalous measurements in $B_s-\bar{B}_s$ mixing: the role of CPT-conserving and CPT-violating new physics

Abstract

Recently observed anomalies in the $B_s \to J/\psi \phi$ 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 $\Gamma_{12}$ of the NP contribution to the effective Hamiltonian. We constrain these parameters using the four observables $\Delta M_s$, $\Delta\Gamma_s$, the mixing phase $\beta_s^{J/\psi\phi}$, 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 $B_s \to \tau^+ \tau^-$.Comment: The final version to be published in PRD. Earlier results updated (strengthened) with 9.1 fb^{-1} data from D