Particle-antiparticle mixing, CP violation and rare K and B decays in a minimal theory of fermion masses

Abstract

We present a detailed study of Delta F=2 observables and of rare K^+(K_L) and B_{s,d} meson decays in a "Minimal Theory of Fermion Masses" (MTFM). In this theory Yukawa couplings are generated through the mixing with heavy vectorlike (VF) fermions. This implies corrections to the SM quark couplings to W, Z and Higgs so that FCNC processes receive contributions from tree level Z and Higgs exchanges and W bosons couple to right-handed quarks. In a particular version of this model in which the Yukawa matrix lambda^D in the heavy down fermion sector is unitary, lambda^U =1 and M = M_{VF} is fixed, only three real and positive definite parameters describe New Physics (NP) contributions to all Delta F=2 and Delta F=1 observables in K and B_{s,d} systems once the known quark masses and the CKM matrix are correctly reproduced. For M>1 TeV NP contributions to B_{s,d}^0- bar{B}_{s,d}^0 mixings are found to be very small. While in principle NP contributions to epsilon_K and Delta F=1 processes could be large, the correlation between epsilon_K and K_L->mu^+ mu^- eliminates basically NP contributions to epsilon_K and right-handed current contributions to Delta F=1 FCNC observables. We find CMFV structure in B_{s,d} decays with BR(B_{s,d}->mu^+ mu^-) uniquely enhanced for M=3 TeV by at least 35% and almost up to a factor of two over their SM values. Also BR(K^+->pi^+ bar{nu} nu) and BR(K_L->pi^0 bar{nu} nu)$ are uniquely enhanced by similar amount but the correlation between them differs from the CMFV one. We emphasize various correlations between K and B_{s,d} decays that could test this scenario. The model favours gamma=68{\deg}, |V_{ub}|=0.0037, S_{psi K_S}=0.72, S_{psi phi}=0.04 and 4.2*10^-9<BR(B_s->mu^+ mu^-)<5.0*10^-9 for M=3-4 TeV.