Enhanced CP asymmetries in $B \to K \mu^+ \mu^-$

TL;DR

This paper explores how complex New Physics couplings can explain anomalies in B meson decays and predicts enhanced CP asymmetries near resonance peaks, providing a potential signal of physics beyond the Standard Model.

Contribution

It demonstrates that complex NP couplings can account for experimental anomalies and predicts measurable CP asymmetries near resonance peaks, offering new tests for beyond Standard Model physics.

Findings

Complex NP couplings can explain $R_K$ and $R_{K^*}$ anomalies.

CP asymmetry is enhanced near $J/\psi$ and $\psi(2S)$ resonances.

Measuring CP asymmetry around resonance peaks can reveal CP violation from New Physics.

Abstract

We show that the current values of $R_K^\mathrm{exp}$ and $R_{K^\ast}^\mathrm{exp}$ can be accommodated by allowing a nonzero New Physics coupling $\delta C_9^{\mu\mu}$ to be complex, both in the scenario in which only $\delta C_9^{\mu\mu}$ is affected, and in the scenario with complex $\delta C_{9,10}^{\mu\mu}$ satisfying $\delta C_{9}^{\mu\mu}=-\delta C_{10}^{\mu\mu}$. A presence of the weak CP-violating phase can then be tested by measuring the CP-asymmetry, $\mathcal{A}_\mathrm{CP}$. We show that this asymmetry is enhanced around the peak of each $c\bar c$-resonance, and in fact more pronounced in the close vicinity of $J/\psi$ and $\psi(2S)$. Therefore, measuring $\mathcal{A}_\mathrm{CP}$ before and after the resonances' peak could be revelatory of the CP-violation that originates from beyond the Standard Model, or to be a significant constrain when building a realistic scenario of New Physics.