Search for direct $CP$ violation in charged charmless $B \to PV$ decays

TL;DR

This paper reports the first observation of direct CP violation in charged B meson decays to PV final states, using a novel method that avoids full amplitude analysis, based on LHCb data at 13 TeV.

Contribution

It introduces a new approach to measure CP asymmetry in B to PV decays without full amplitude analysis, applied to LHCb data at 13 TeV.

Findings

First observation of CP violation in B+ → ρ(770)^0 K+ decay.

Measured CP asymmetry in this decay is +0.150 ± 0.019 ± 0.011.

Other decay channels show CP asymmetries compatible with zero.

Abstract

Measurements of $CP$ asymmetry in charmless $B\to PV$ decays are presented, where $P$ and $V$ denote a pseudoscalar and a vector meson, respectively. Five different $B\to PV$ decays from four final states, $B^\pm \to \pi^\pm \pi^+ \pi^-$, $B^\pm \to K^\pm \pi^+ \pi^-$, $B^\pm \to K^\pm K^+ K^-$ and $B^\pm \to \pi^\pm K^+ K^-$ are analyzed. The measurements are based on a method that does not require full amplitude analyses, and are performed using proton-proton collision data at a center-of-mass energy of 13 TeV collected by LHCb between 2015 and 2018, corresponding to an integrated luminosity of 5.9 fb$^{-1}$. In the $\pi^+ \pi^-$ $\textit{P}$-wave, in the region dominated by the $B^\pm \to \rho(770)^0 K^\pm$ decay, a $CP$ asymmetry of $\mbox{$A_{CP}$ = +0.150 $\pm$ 0.019 $\pm$ 0.011}$ is measured, where the first uncertainty is statistical and the second is systematic. This is the first observation of $CP$ violation in this process. For the other four decay channels, in regions dominated by the $B^\pm \to \rho(770)^0 \pi^\pm$, $B^\pm \to \overset{(-)}{K^*}(892)^0 \pi^\pm$, $B^\pm \to \overset{(-)}{K^*}(892)^0 K^\pm$ and $B^\pm \to \phi(1020) K^\pm$ decays, $CP$ asymmetries in the $\textit{P}$-wave compatible with zero are measured.