Study of X(3872) in $B$ meson decays

TL;DR

This paper reports the first significant observation of X(3872) production in B0 decays, measures branching ratios and mass differences, and searches for related decay modes using Belle data, providing insights into the nature of X(3872).

Contribution

It presents the first significant observation of X(3872) in B0 decays and measures related branching ratios and mass differences, advancing understanding of X(3872) production.

Findings

First statistically significant observation of B0 → X(3872) K0_S

Branching ratio of B0 to B+ decay modes consistent with unity

Mass difference between X(3872) states in B+ and B0 decays consistent with zero

Abstract

We present results on the X(3872), produced in $B^+ \to X(3872) K^+$ and $B^0 \to X(3872) K^0_S$ decays where $X(3872) \to J/\psi \pi^+ \pi^-$. We report the first statistically significant observation of $B^0 \to X(3872) K^0_S$ and measure the ratio of branching fractions to be $\frac{{\cal B}(B^0 \to X(3872)K^0)} {{\cal B}(B^+ \to X(3872)K^+)} = 0.82 \pm 0.22 \pm 0.05$, consistent with unity. The mass difference between the X(3872) states produced in $B^+$ and $B^0$ decay is found to be $\delta M \equiv M_{XK^+} - M_{XK^0} = (+0.18 \pm 0.89 \pm 0.26)$ MeV/$c^2$, consistent with zero. In addition, we search for the X(3872) in the decay $B^0 \to X(3872)K^+\pi^-$, $X(3872) \to J/\psi \pi^+ \pi^-$. We measure ${\cal B}(B^0 \to X(3872) (K^+ \pi^-)_{NR}) \times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) = (8.1 \pm 2.0 ^{+1.1}_{-1.4})\times 10^{-6}$ and we set the 90% C.L. limit, ${\cal B}(B^0 \to X(3872)K^{*}(892)^0) \times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) < 3.4 \times 10^{-6}$. The analysis is based on a 605 fb$^{-1}$ data sample collected at the $\Upsilon(4S)$ with the Belle detector at the KEKB collider.