Measurement of $CP$ observables in $B^\pm \to D^{(*)} K^\pm$ and $B^\pm \to D^{(*)} \pi^\pm$ decays

TL;DR

This paper reports precise measurements of $CP$ violation observables in various $B^ ext{±}$ decays involving $D^{(*)}$ mesons, using partial and full reconstruction methods with data from the LHCb experiment, advancing understanding of matter-antimatter asymmetry.

Contribution

First partial reconstruction analysis of $B^{ ext{±}} o D^{*} K^{ ext{±}}$ and $B^{ ext{±}} o D^{*} ext{π}^{ ext{±}}$ decays, and updated precise measurements of $B^{ ext{±}} o D K^{ ext{±}}$ and $B^{ ext{±}} o D ext{π}^{ ext{±}}$ decays.

Findings

First of its kind partial reconstruction analysis for $B^{ ext{±}} o D^{*} K^{ ext{±}}$ and $B^{ ext{±}} o D^{*} ext{π}^{ ext{±}}$ decays.

Most precise measurements of $B^{ ext{±}} o D K^{ ext{±}}$ to date.

Updated $CP$ observables consistent with Standard Model expectations.

Abstract

Measurements of $CP$ observables in $B^\pm \rightarrow D^{(*)} K^\pm$ and $B^\pm \rightarrow D^{(*)} \pi^\pm$ decays are presented, where $D^{(*)}$ indicates a neutral $D$ or $D^*$ meson that is an admixture of $D^{(*)0}$ and $\bar{D}^{(*)0}$ states. Decays of the $D^*$ meson to the $D\pi^0$ and $D\gamma$ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the $B$ candidate invariant mass distribution. Decays of the $D$ meson are fully reconstructed in the $K^\pm \pi^\mp$, $K^+ K^-$ and $\pi^+ \pi^-$ final states. The analysis uses a sample of charged $B$ mesons produced in $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb$^{-1}$ taken at centre-of-mass energies of $\sqrt{s}$ = 7, 8 and 13 TeV, respectively. The study of $B^{\pm} \to D^{*} K^{\pm}$ and $B^{\pm} \to D^{*} \pi^{\pm}$ decays using a partial reconstruction method is the first of its kind, while the measurement of $B^{\pm} \to D K^{\pm}$ and $B^{\pm} \to D \pi^{\pm}$ decays is an update of previous LHCb measurements. The $B^{\pm} \to D K^{\pm}$ results are the most precise to date.