Family nonuniversal Z′ effects on Bd,s→K*0K¯*0 decays in perturbative QCD approach

Abstract

The nonleptonic decays ${B}_{d,s}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0}$ are reanalyzed in perturbative QCD approach, which is based on the ${k}_{\mathrm{T}}$ factorization. In the Standard Model, the calculated branching fraction and longitudinal polarization fraction of ${B}_{d}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0}$ are in agreement with experimental measurements, while the predictions of ${B}_{s}\ensuremath{\rightarrow}{K}^{*0}{\overline{K}}^{*0}$ cannot agree with data simultaneously. The parameter that combines longitudinal polarization fractions and branching fractions is calculated to be ${L}_{{K}^{*}{\overline{K}}^{*0}}^{\mathrm{PQCD}}={12.7}_{\ensuremath{-}3.2}^{+5.6}$, which is also larger than that extracted from experimental measurements. We then study all observables by introducing a family nonuniversal ${Z}^{\ensuremath{'}}$ boson in $b\ensuremath{\rightarrow}sq\overline{q}$ transitions. In order to reduce the number of new parameters, we simplify the model as possible. It is found that with the fixed value ${\ensuremath{\omega}}_{{B}_{s}}=0.55$, these exists parameter space where all measurements, including the branching fraction, longitudinal polarization fraction, and ${L}_{{K}^{*}{\overline{K}}^{*0}}$-parameter, could be accommodated simultaneously. All our results and the small parameter space could be further tested in the running LHC experiment, Belle-II, and future high-energy colliders.