Measurement of $C\!P$ observables in $B^\pm \rightarrow D K^\pm$ and $B^\pm \rightarrow D \pi^\pm$ with two- and four-body $D$ decays

TL;DR

This paper reports measurements of CP violation in B meson decays involving D mesons reconstructed in multiple final states, including the first analysis of the four-pion D decay mode, providing key input for the unitarity triangle angle gamma.

Contribution

It presents the first analysis of CP observables in B decays with D mesons decaying to four pions and combines multiple decay modes to improve the determination of gamma.

Findings

Observation of CP-violating effects in various decay modes

First measurement involving four-pion D decay mode

Results contribute to constraining the unitarity triangle angle gamma

Abstract

Measurements of $C\!P$ observables in $B^\pm \rightarrow D K^\pm$ and $B^\pm \rightarrow D \pi^\pm$ decays are presented where the $D$ meson is reconstructed in the final states $K^\pm\pi^\mp$, $\pi^\pm K^\mp$, $K^+K^-$, $\pi^+\pi^-$, $K^\pm\pi^\mp \pi^+ \pi^-$, $\pi^\pm K^\mp \pi^+ \pi^-$ and $\pi^+ \pi^- \pi^+ \pi^-$. This analysis uses a sample of charged $B$ mesons from $pp$ collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb$^{-1}$. Various \CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle $\gamma$. The analysis of the four-pion $D$ decay mode is the first of its kind.