Correlations among new CP violating effects in Delta F = 2 observables

Abstract

We point out that the observed CP violation in Bd - bar{Bd} mixing, taking into account the measured ratio Delta Md / Delta Ms, the recently improved lattice value of the non-perturbative parameter BK and an additional effective suppression factor kappa_epsilon ~= 0.92 in epsilon_K neglected sofar in most analyses, may be insufficient to describe the measured value of epsilon_K within the Standard Model (SM), thus hinting at new CP violating contributions to the K - bar{K} and/or Bd - bar{Bd} systems. Furthermore, assuming that Delta Md / Delta Ms is SM-like, the signs and the magnitudes of new physics effects in epsilon_K and in the CP asymmetries S_{psi Ks} and S_{psi phi} may turn out to be correlated. For example, in a scenario with new CP-phases in Bd and Bs mixings being approximately equal and negative, a common new phase ~= - 5 degrees could remove the tension between epsilon_K and S_{psi Ks} present in the SM and simultaneously accommodate, at least partly, the recent claim of S_{psi phi} being much larger than the SM expectation. We emphasize the importance of precise determinations of Vcb, BK, FK and xi_s, to which the parameter epsilon_K and its correlation with the CP violation in the Bd - bar{Bd} system are very sensitive.