Measurements of time-dependent CP asymmetries in $B \to D^{*\mp} \pi^{\pm}$ decays using a partial reconstruction technique

TL;DR

This study measures time-dependent CP asymmetries in B meson decays to D* pi using a partial reconstruction method, providing precise CP violation parameters with data from the Belle detector.

Contribution

It introduces a partial reconstruction technique for measuring CP asymmetries in B decays, improving analysis efficiency and precision over previous methods.

Findings

CP violation parameters S+ = +0.061 ± 0.018 (stat) ± 0.012 (syst)

CP violation parameters S- = +0.031 ± 0.019 (stat) ± 0.015 (syst)

Successful application of partial reconstruction in a large data sample

Abstract

We report results on time-dependent CP asymmetries in $B \to D^{*\mp}\pi^{\pm}$ decays based on a data sample containing 657 {\times} $10^6$ $B\bar{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider at the $\Upsilon(4S)$ resonance. We use a partial reconstruction technique, wherein signal $B \to D^{*\mp}\pi^{\pm}$ events are identified using information only from the fast pion from the B decay and the slow pion from the subsequent decay of the $D^{*\mp}$, where the former (latter) corresponds to $D^{*+} (D^{*-})$ final states. We obtain CP violation parameters $S^+ = +0.061 \pm 0.018(\mathrm{stat}) \pm 0.012(\mathrm{syst})$ and $S^- = +0.031 \pm 0.019(\mathrm{stat}) \pm 0.015(\mathrm{syst})$.