Observation of $B^{\pm} \to \psi(2S) \pi^{\pm}$ and search for direct CP-violation

TL;DR

This paper reports the first observation of the decay B± to ψ(2S)π±, measures its branching fraction and charge asymmetry, and searches for direct CP violation using a large dataset from the Belle detector.

Contribution

First observation of B± to ψ(2S)π± decay, with measurements of branching fraction, charge asymmetry, and decay ratio, providing new insights into suppressed B meson decays.

Findings

Branching fraction measured as (2.44 ± 0.22 ± 0.20)×10^{-5}

Charge asymmetry consistent with zero, indicating no direct CP violation detected

Decay ratio of B± to ψ(2S)π± relative to B± to ψ(2S)K± is approximately 4%

Abstract

We report the first observation of $B^{\pm}\to\psi(2S)\pi^{\pm}$, a Cabibbo- and color-suppressed decay. This analysis is based on $657\times10^{6}$ $B\overline B$ events collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB energy-asymmetric $e^+e^-$ collider. The measured branching fraction is ($2.44 \pm 0.22 \pm 0.20$)$\times 10^{-5}$ and the charge asymmetry is $\mathcal{A}=0.022 \pm 0.085 \pm 0.016$. The ratio of the branching fractions $\mathcal {B}(B^{\pm} \to \psi(2S) \pi^{\pm})$$/ \mathcal {B}(B^{\pm} \to \psi(2S) K^{\pm})$ $ = (3.99 \pm 0.36\pm 0.17)%$ is also determined.