Evidence for B- -> Ds+ K- l- nubar and search for B- -> Ds*+ K- l- nubar

TL;DR

This paper reports the first evidence and measurements of specific semileptonic B- decays involving Ds+ K- final states, providing new insights into B meson decay processes and invariant mass distributions.

Contribution

It provides the first evidence for B- -> Ds+ K- l- nubar decay and measures its branching fraction, along with the first measurement of the Ds+ K- invariant mass distribution.

Findings

Evidence for B- -> Ds+ K- l- nubar with 3.4 sigma significance

Measured branching fractions for B- -> Ds+ K- l- nubar and B- -> Ds*+ K- l- nubar

Ds+ K- invariant mass distribution peaks around 2.6 GeV/c^2

Abstract

We report measurements of the decays B- -> Ds(*)+ K- l- nubar in a data sample containing 657x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal with a significance of 6 sigma for the combined Ds and Ds* modes and find the first evidence of the B- -> Ds+ K- l- nubar decay with a significance of 3.4 sigma. We measure the following branching fractions: BF(B- -> Ds+ K- l nubar) = (0.30 +/- 0.09(stat) +0.11 -0.08(syst)) x 10^-3 and BF(B- -> Ds*+ K- l- nubar) = (0.59 +/- 0.12(stat) +/- 0.15(syst)) x 10^-3 and set an upper limit BF(B- -> Ds*+ K- l- nubar) < 0.56 x 10^-3 at the 90% confidence level. We also present the first measurement of the Ds+K- invariant mass distribution in these decays, which is dominated by a prominent peak around 2.6 GeV/c^2.