Unpolarized and longitudinally polarized lepton forward-backward asymmetries inB→K*l+l−decay in the fourth-generation standard model

Abstract

We investigate the influence of the fourth-generation quarks on the asymmetries for unpolarized and polarized leptons in $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decay. We obtain that for both ($\ensuremath{\mu}$, $\ensuremath{\tau}$) channels the magnitudes of the differential forward-backward (FB) asymmetries and the average forward-backward asymmetries are quite sensitive to the fourth-generation quarks' mass and mixing parameters. We also achieve that, among the double lepton polarization FB asymmetries, just longitudinally polarized leptons' FB asymmetry shows considerable discrepancy with respect to the third-generation standard model. Moreover, we find that longitudinally polarized leptons' FB asymmetry and its variation with new fourth-generation standard model parameters coincide with unpolarized FB when the lepton mass vanishes. The study of FB asymmetries can serve as a good tool to search for new-physics effects, precisely, to search for the fourth-generation quarks (${t}^{\ensuremath{'}}$, ${b}^{\ensuremath{'}}$) via its indirect manifestations in the loop diagrams.