The B_{s0} meson and the B_{s0}B K coupling from QCD sum rules

TL;DR

This paper uses QCD sum rules to estimate the mass and coupling of the $B_{s0}$ meson, comparing different structural hypotheses, and finds that decay width measurements can distinguish its true nature.

Contribution

It provides a novel QCD sum rule analysis of the $B_{s0}$ meson as a tetraquark and as a $bar{s}$ state, offering insights into its structure.

Findings

Mass of $B_{s0}$ meson is about 6.04 GeV, larger than some models.

Coupling constant $g_{B_{s0} B K}$ is approximately 16.3 GeV.

Decay width varies significantly between tetraquark and molecular models.

Abstract

We evaluate the mass of the $B_{s0}$ scalar meson and the coupling constant in the $B_{s0} B K$ vertex in the framework of QCD sum rules. We consider the $B_{s0}$ as a tetraquark state to evaluate its mass. We get $m_{B_s0}=(6.04\pm 0.08) \GeV$, which is bigger than predictions supposing it as a $b\bar{s}$ state or a $B\bar{K}$ bound state with $J^{P}=0^+$. To evaluate the $g_{B_{s0}B K}$ coupling we use the three point correlation functions of the vertex, considering $ B_{s0} $ as a normal $b\bar{s}$ state. The obtained coupling constant is: $g_{B_{s0} B K} =(16.3 \pm 3.2) \GeV$. This number is in agreement with light-cone QCD sum rules calculation. We have also compared the decay width of the $\BS\to BK$ process considering the $\BS$ to be a $b\bar{s}$ state and a $BK$ molecular state. The width obtained for the $BK$ molecular state is twice as big as the width obtained for the $b\bar{s}$ state. Therefore, we conclude that with the knowledge of the mass and the decay width of the $\BS$ meson, one can discriminate between the different theoretical proposals for its structure.