Observation of Y(3940) -> J/psi omega in B -> J/psi omega K at BABAR

TL;DR

This paper reports the observation of the Y(3940) resonance in B meson decays to J/psi omega K, measuring its mass, width, and branching fractions using a large dataset from the BABAR experiment.

Contribution

First observation of Y(3940) in B decays with precise measurements of its mass, width, and decay ratios, expanding understanding of this exotic state.

Findings

Y(3940) mass measured at 3914.6 MeV/c^2

Y(3940) width measured at 34 MeV

Branching fractions for B decays involving Y(3940) reported

Abstract

We present a study of the decays $B^{0,+}\to J/\psi\omega K^{0,+}$ using $383\times 10^{6}$ $B\bar{B}$ events obtained with the \babar detector at PEP-II. We observe $Y(3940) \to J/\psi \omega$, with mass $3914.6 ^{+3.8}_{-3.4} (stat) \pm{2.0} (syst)$ \mevcc, and width $34^{+12}_{-8}(stat)\pm{5}(syst)$ \mev. The ratio of $B^0$ and $B^+$ decay to $YK$ is $0.27^{+0.28}_{-0.23}(stat)^{+0.04}_{-0.01}(syst)$, and the relevant $B^0$ and $B^+$ branching fractions are reported.