New Physics in Gamma_12^s: (sbar b) (taubar tau) Operators
  Measurements performed at the Tevatron of both the like-sign dimuon charge asymmetry in B_d,s-meson samples and the mixing-induced CP asymmetry in B_s -> J/psi phi depart from their standard model (SM) predictions. This could be an indication for new CP phases in Delta B = 2 transitions, preferentially in B_s-Bbar_s mixing. The experimental situation, however, remained inconclusive, as it favored values of the element Gamma_12^s of the decay matrix in the B_s-meson system that are notably different from the SM expectation, suggesting the presence of new physics in the Delta B = 1 sector as well. The very recent LHCb measurements of B_s -> J/psi phi and B_s -> J/psi f_0, which do not find any evidence for a new-physics phase in the element M_12^s of the mass matrix, point into this direction as well. In this article, we explore the potential size of non-standard effects in Gamma_12^s stemming from dimension-six operators with flavor content (sbar b) (taubar tau). We show that since the existing constraints imposed by tree- and loop-level mediated B_d,s-meson decays are quite loose, absorptive new physics of this type can in part explain the current data. Our model-independent conclusions are finally contrasted with explicit analyses of the new-physics effects in B_s-Bbar_s mixing that can arise from leptoquarks or Z' bosons. 
Christoph Bobeth and Ulrich Haisch
hep-ph hep-ex