Angular analysis of the $B^+\to\pi^+\mu^+\mu^-$ decay

TL;DR

This paper reports the first measurement of angular observables in the decay $B^+ o ext{pi}^+ ext{mu}^+ ext{mu}^-$ using LHCb data, testing Standard Model predictions in different mass regions.

Contribution

It provides the first measurement of $A_{FB}$ and $F_H$ angular parameters for this decay, expanding understanding of rare B meson decays.

Findings

Measured $A_{FB}$ and $F_H$ in two dimuon mass regions.

Results are consistent with Standard Model within confidence intervals.

Analysis uses 9 fb$^{-1}$ of LHCb data from 2011-2018.

Abstract

This paper presents the first measurement of the forward-backward asymmetry, $A_{\rm FB}$, and the flat term, $F_{H}$, that parameterise the angular distribution of the $B^+\to\pi^+\mu^+\mu^-$ decay. The proton-proton collision dataset used in the analysis corresponds to an integrated luminosity of 9 fb$^{-1}$, collected with the LHCb experiment between 2011 and 2018. The analysis is performed in two intervals of dimuon mass squared, one above and one below the region containing the $J\mskip -3mu/\mskip -2mu\psi$ and $\psi(2S)$ narrow charmonium resonances. The Standard Model predictions lie within the obtained $68\%$ confidence level interval in the high-mass and within the $99\%$ interval in the low-mass region.