Implications of the top quark mass measurement for the CKM parameters,x s and CP asymmetries

Motivated by the recent determination of the top quark mass by the CDF collaboration,m _t =174±10 _?12 ⁺¹³ GeV, we review and update the constraints on the parameters of the quark flavour mixing matrixV _CKM in the standard model. In performing our fits, we use inputs from the measurements of the following quantities: (i) |∈|, the CP-violating parameter inK decays, (ii) ΔM _d , the mass difference due to the $B_d^0 - overline {B_d^0 }$ mixing, (iii) the matrix elements |V _cb | and |V _ub |, and (iv)B-hadron lifetimes. We find that the allowed region of the unitarity triangle is very large, mostly due to theoretical uncertainties. (This emphasizes the importance of measurements of CP-violating rate asymmetries in theB system.) Nevertheless, the present data do some-what restrict the allowed values of the coupling constant product $f_{B_d } sqrt {hat B_{B_d } }$ and the renormalization-scale-invariant bag constant $hat B_K$ . With the updated CKM matrix we present the currently-allowed range of the ratio |V _td /V _ts |, as well as the standard model predictions for the $B_s^0 - overline {B_s^0 }$ mixing parameterx _s and the quantities sin 2α, sin 2β and sin² γ, which characterize the CP-asymmetries inB-decays. The ALEPH collaboration has recently reported a significant improvement on the lower limit on the $B_s^0 - overline {B_s^0 }$ mass difference, ΔM _s /Δx _d >11.3 (95% C.L.). This has interesting consequences for the CKM parameters which are also worked out.