We consider the two-Higgs-doublet model as a framework in which to evaluate the viability of scenarios in which the sign of the coupling of the observed Higgs boson to down-type fermions (in particular, b-quark pairs) is opposite to that of the Standard Model (SM), while at the same time all other tree-level couplings are close to the SM values. We show that, whereas such a scenario is consiste...

I discuss the results of a new calculation of the charm and bottom quark masses in the quenched approximation and in the continuum limit of lattice QCD. The work has been done by the APE group at the “Tor Vergata” University [1] making use of the step scaling method, previously introduced to deal with two scale problems, that allows to take the continuum limit of the lattice data. We have compu...

Standard Model fits are performed on the most recent leptonic and b quark Z decay data from LEP and SLD, and FERMILAB data on top quark production, to obtain m t and m H. Poor fits are obtained, with confidence levels ≃ 2%. Removing the b quark data improves markedly the quality of the fits and reduces the 95% CL upper limit on m H by ≃ 50 GeV.

Standard Model fits are performed on the most recent leptonic and b quark Z decay data from LEP and SLD, and FERMILAB data on top quark production, to obtain m t and m H. Poor fits are obtained, with confidence levels ≃ 2%. Removing the b quark data improves markedly the quality of the fits and reduces the 95% CL upper limit on m H from 169 GeV to 110 GeV.

We study a model Dyson-Schwinger equation for the quark propagator closed using an Ansatz for the gluon propagator of the form D(q) ∼ q2/[(q2)2 + b4] and two Ansätze for the quark-gluon vertex: the minimal Ball-Chiu and the modified form suggested by Curtis and Pennington. Using the quark condensate as an order parameter, we find that there is a critical value of b = bc such that the model does...

The decay constant fB is being studied extensively on the lattice because of its importance for the determination of CKM matrix elements. The spectrum of excited B mesons and b baryons is being measured in present experiments, whereas there exist only few lattice results on this subject. In this article we report on our study of B mesons in two-flavor full QCD employing the NRQCD action for hea...

We discuss the problem of the large discrepancy between the observed lifetime ratio of Bd to b and the theoretical prediction obtained by the heavy quark e ective theory. A new possibility of solving this problem is proposed from the viewpoint of operator product expansion and the lifetime ratio of b to b is predicted. The heavy quark e ective theory (HQET) is successful in explaining various n...