$C\!P$ violation analysis of local and nonlocal amplitudes in the $\overline{B}^0 \to \overline{K}^{*0}\mu^+\mu^-$ decay

TL;DR

This study searches for $CP$ violation in the decay $ar{B}^0 o ar{K}^{*0}\mu^+\mu^-$ using LHCb data, analyzing angular distributions and Wilson coefficients, finding no significant $CP$ violation and confirming Standard Model consistency.

Contribution

It provides the most precise measurements to date of $CP$-violating effects in this decay, utilizing full angular analysis and nonlocal hadronic amplitudes.

Findings

No significant $CP$ violation observed.

Precision of $CP$-violation observables improved by an order of magnitude.

Results are consistent with Standard Model expectations.

Abstract

A search for $C\!P$ violation in the $\overline{B}^0 \to \overline{K}^{*0}\mu^+\mu^-$ decay is performed using proton--proton collision data collected by the LHCb experiment during Run 1 and Run 2, corresponding to an integrated luminosity of 8.4 fb$^{-1}$. The analysis exploits the full angular distribution of the decay, providing sensitivity to $C\!P$-violating effects in both vector and axial-vector contributions to this flavour-changing neutral-current process. The complex Wilson coefficients are determined within the Weak Effective Theory through an unbinned maximum-likelihood fit to the angular observables, incorporating nonlocal hadronic amplitudes across the full dimuon mass spectrum. The precision of the $C\!P$-violation observables is improved by an order of magnitude relative to previous measurements, with the imaginary parts of the Wilson coefficients now determined more precisely than the real parts. No significant $C\!P$ violation is observed, and the results are consistent with Standard Model.