6533b832fe1ef96bd129ac14

RESEARCH PRODUCT

Small violations of 3 × 3 unitarity, the phase inB0s–B̄0smixing and visiblet → cZdecays at the LHC

subject

description

We show that it is possible to accommodate the observed size of the phase in Bs0?s0 mixing in the framework of a model with violation of 3 ? 3 unitarity. This violation is associated to the presence of a new Q = 2/3 isosinglet quark T, which mixes both with t and c and has a mass not exceeding 500 GeV. The crucial point is the fact that this framework allows for ? ? arg(?VtsVcbV*tbV*cs) of order ?, to be contrasted with the situation in the Standard Model, where ? is constrained to be of order ?2. We point out that this scenario implies rare top decays t?cZ at a rate observable at the LHC and |Vtb| significantly different from unity. In this framework, one may also account for the observed size of D0?0 mixing without having to invoke long distance contributions. It is also shown that in the present scenario, the observed size of D0?0 mixing constrains ?' ? arg(?VcdVusVcs*V*ud) to be of order ?4, which is significantly smaller than what is allowed in generic models with violations of 3 ? 3 unitarity.