K^+\toπ^+ν\barν with four generations and its effects on unitarity triangle

Abstract

We analyze in the four-generation model the first measurement of the branching ratio of rare kaon decay K^+\toπ^+ν\barν, using the constraints from Δm_K, ε_K, B_d-\bar{B_d} mixing, Γ(b\to sγ), B_s-\bar{B_s} mixing, D^0-\bar{D^0} mixing, B(K_L\toπ^0ν\barν) and B(K_L\toμ\barμ), and study its effects on the unitarity triangle. With the results of searching for the maximum mixing of the fourth generation, we predict that D^0-\bar{D^0} mixing Δm_D and the branching ratio of "direct" CP-violating decay process K_L\toπ^0ν\barν could attain the values 1-2 orders of magnitude larger than the predictions of the Standard Model.