Evidence for the $b\to u$ Transition $B^0\to D_s^+ pi^-$ and a Search for $B^0\to D_s^*+ pi^-$

TL;DR

This paper provides evidence for the rare $b o u$ transition in $B^0$ decays, measuring its branching fraction and setting limits on related decay modes, using data from the BaBar experiment.

Contribution

First evidence for the $B^0 o D_s^{+} o ext{pi}$ decay, with a measured branching fraction and a new limit on the $B^0 o D_s^{*+} o ext{pi}$ decay, advancing understanding of $b o u$ transitions.

Findings

Evidence for $B^0 o D_s^{+} o ext{pi}$ with 3.5 sigma significance.

Measured branching fraction $B^0 o D_s^{+} o ext{pi} = 3.1 imes 10^{-6}$.

Upper limit for $B^0 o D_s^{*+} o ext{pi}$ set at $4.3 imes 10^{-5}$.

Abstract

We report evidence for the $b\to u$ transition $B^0 \to D_s^{+}\pi^-$ and the results of a search for $B^0 \to D_s^{*+} \pi^-$ from a sample of $61.6\times 10^6$ $Y(4S)$ decays into $B$ meson pairs collected with the BaBar detector at the PEP II asymmetric $e^{+}e^{-}$ collider. The observed $B^0 \to D_s^{+} \pi^-$ yield has a probability of $4.4 \times 10^{-4}$ to be a fluctuation of the background (3.5 $\sigma$) and we measure the branching fraction $B^0 \to D_s^{+} \pi^-=3.1 \pm 1.0 ({\rm stat.})\pm 1.0 ({\rm syst.})$. We also set a limit $B^0 \to D_s^{*+} \pi^- <~4.3\times 10^{-5}$ at 90% C.L.