Study of $B\to K^{(*)} \ell^+\ell^-$ Decays in the Family Non-universal $Z'$ Models

TL;DR

This paper investigates how family non-universal $Z'$ models can explain anomalies in $B o K^{(*)}\,\ell^+\ell^-$ decays, constraining model parameters and predicting $B_s\to\mu^+\mu^-$ branching ratios close to experimental bounds.

Contribution

It provides new constraints on $Z'$ couplings from $B$ decay data and demonstrates the model's ability to explain observed asymmetries and predict decay rates.

Findings

Explains the forward-backward asymmetry in $B\to K^*\ell^+\ell^-$ decays.

Predicts $B_s\to\mu^+\mu^-$ branching ratio near current experimental upper bounds.

Constrains $Z'$ model parameters consistent with observed decay phenomena.

Abstract

In a combined investigation of the $B\to K^{(*)}\ell^+\ell^-$ decays, constraints on the related couplings in family non-universal $Z^{\prime}$ models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the $B\to K^*\ell^+\ell^-$ decay can be explained, by flipping the signs of the Wilson coefficients $C_9^{\rm eff}$ and $C_{10}$. With the obtained constraints, we also calculate the branching ratio of the $B_s\to\mu^+\mu^-$ decay. The upper bound of our prediction is near the upper bound given by CDF Collaboration recently.