CP VIOLATION FROM NEW QUARKS IN THE CHIRAL LIMIT

We characterize CP violation in the SU(2) x U(1) model due to an extra vector-like quark or sequential family, giving special emphasis to th e chiral limit m(u,d,s) = 0. In this limit, CP is conserved in the thr ee-generation Standard Model (SM), thus implying that all CP violation is due to the two new CP violating phases whose effects may manifest either at high energy in processes involving the new quark or as devia tions from SM unitarity equalities among imaginary parts of invariant quartets (or, equivalently, areas of unitarity triangles). In our anal ysis we use an invariant formulation, independent of the choice of wea k quark basis or the phase convention in the generalized Cabibbo-Kobay ashi-Maskawa matrix. We identify the three weak-basis invariants, as w ell as the three imaginary parts of quartets B1-3 which, in the chiral limit, give the strength of CP violation beyond the SM. We find that for an extra vector-like quark \ B-i \ less than or equal to 10(-4), w hereas for an extra sequential family \ Bi \ less than or equal to 10( -2). (C) 1998 Elsevier Science B.V.