Study of the semileptonic decays $Υ(1S)→ B(c)ν̄_$

We study the exclusive semileptonic decays Υ(1S)→ B(c)ν̄_, where = e,μ,τ. The relevant hadronic form factors are calculated using the Covariant Confined Quark Model developed previously by our group. We predict the branching fractions B(Υ(1S)→ B(c)ν̄₎ to be of the order of 10⁻¹³ and 10⁻¹⁰ for the case of B and Bc, respectively. Our predictions agree well with other theoretical calculations. We also consider the effects of possible New Physics in the case of Υ(1S)→ Bcτν̄_τ. We show that the branching fraction of this decay can be enhanced by an order of magnitude using the constraints from the B→ D(*)ν̄_ and Bc→ J/ψ ν̄_ experimental data.