Reconciling anomalous measurements in B_s − B̅_s mixing: the role of CPT-conserving and CPT-violating new physics

Abstract

Recently observed anomalies in the B_s→J/ψφ decay and the like-sign dimuon asymmetry A^b_sl hint at possible new physics (NP) in the B_s − B̅_s mixing. We parameterize the NP with four model-independent quantities: the magnitudes and phases of the dispersive part M₁₂ and the absorptive part Γ₁₂ of the NP contribution to the effective Hamiltonian. We constrain these parameters using the four observables ΔM_s, Γ_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 B_s − B̅_s mixing therefore seems to be essential, and would imply a large branching fraction for channels like B_s→ τ⁺τ⁻.