Measurement of the local and nonlocal amplitudes in $B^{+}\to K^{+}\mu^{+}\mu^{-}$ decays

TL;DR

This study analyzes the local and nonlocal amplitudes in the decay $B^+ o K^+\mu^+\mu^-$ using LHCb data, providing insights into short- and long-distance effects and testing Standard Model predictions.

Contribution

It introduces a comprehensive amplitude analysis model for the entire dimuon mass spectrum in $B^+ o K^+\mu^+\mu^-$ decays, incorporating both one- and two-particle nonlocal amplitudes.

Findings

Compatibility of Wilson coefficients with the Standard Model varies between 1.6σ and 4σ.

The analysis distinguishes short- and long-distance contributions.

The model describes the entire dimuon mass spectrum effectively.

Abstract

This paper presents a thorough study of the local and nonlocal amplitudes in $B^+ \to K^+\mu^+\mu^-$ transitions through an amplitude analysis of the dimuon mass spectrum of the decay. The analysis is based on $pp$ collision data corresponding to an integrated luminosity of 8.4fb$^{-1}$ collected by the LHCb experiment. This measurement employs a model that describes both one-particle and two-particle nonlocal amplitudes across the entirety of the dimuon mass spectrum, enabling the determination of both short- and long-distance contributions to the decay. The compatibility of the Wilson coefficient combinations $C_9+C_9'$ and $C_{10}+C_{10}'$ with the Standard Model prediction is found to vary between $1.6\,\sigma$ and $4\,\sigma$, depending on the choice of local form factors.