First observation of the decays $\bar{B}^0_{(s)}\to D_s^+K^-\pi^+\pi^-$ and $\bar{B}^0_s\to D_{s1}(2536)^+\pi^-$

TL;DR

This paper reports the first observation of specific B meson decays involving D_s^+ and K^-π^+π^- final states, measuring their branching fractions and highlighting their potential for CP violation studies.

Contribution

It presents the first observation and measurement of branching fractions for the decays ^0_s_s^+K^-π^+π^- and ^0_s^+K^-π^+π^-, including a new decay mode involving D_{s1}(2536)^+ which can be used to measure the weak phase .

Findings

Branching fraction of ^0_s_s^+K^-π^+π^- is (5.2 1 0.5 1 0.3) imes 10^{-2}

Branching fraction of ^0_s^+K^-π^+π^- relative to ^0_s_s^+K^-π^+π^- is 0.54 1 0.07 1 0.07

First observation of ^0_s_{s1}(2536)^+_{s1}^+ o D_s^+ ext{ with a relative branching fraction of } (4.0 1 1.0 1 0.4) imes 10^{-3}

Abstract

The first observation of the decays $\bar{B}^0_{s}\to D_s^+K^-\pi^+\pi^-$ and $\bar{B}^0\to D_s^+K^-\pi^+\pi^-$ are reported using an integrated luminosity of 1.0 fb$^{-1}$ recorded by the LHCb experiment. The branching fractions, normalized with respect to $\bar{B}^0_{s}\to D_s^+\pi^-\pi^+\pi^-$ and $\bar{B}^0_{s}\to D_s^+K^-\pi^+\pi^-$, respectively, are measured to be {\br(\bar{B}^0_{s}\to D_s^+K^-\pi^+\pi^-)\over\br(\bar{B}^0_{s}\to D_s^+\pi^-\pi^+\pi^-)} &= (5.2\pm0.5\pm0.3)\times10^{-2}, {\br(\bar{B}^0\to D_s^+K^-\pi^+\pi^-)\over\br(\bar{B}^0_{s}\to D_s^+K^-^\pi^+\pi^-)} &= 0.54\pm0.07\pm0.07, where the first uncertainty is statistical and the second is systematic. The $\bar{B}^0_{s}\to D_s^+K^-\pi^+\pi^-$ decay is of particular interest as it can be used to measure the weak phase $\gamma$. First observation of the $\bar{B}^0_s\to D_{s1}(2536)^+\pi^-, D_{s1}^+\to D_s^+\pi^-\pi^+$ decay is also presented, and its branching fraction relative to $\bar{B}^0_{s}\to D_s^+\pi^-\pi^+\pi^-$ is found to be {\br(\bar{B}^0_s\to D_{s1}(2536)^+\pi^-, D_{s1}^+\to D_s^+\pi^-\pi^+)\over\br(\bar{B}^0_{s}\to D_s^+\pi^-\pi^+\pi^-)} &= (4.0\pm1.0\pm0.4)\times10^{-3}.