Triangle mechanism in the decay process $B_0 \to J/\psi K^0 f_0(980)(a_0(980))$

TL;DR

This paper investigates the triangle mechanism in certain B0 decay processes, revealing a triangle singularity near 1520 MeV and calculating sizable branching fractions, which can shed light on the properties of scalar mesons f0(980) and a0(980).

Contribution

It introduces a detailed analysis of the triangle mechanism in B0 decays, highlighting the singularity and providing quantitative branching fraction predictions.

Findings

Triangle singularity around 1520 MeV identified.

Branching fractions calculated: 1.38×10^{-6} and 2.56×10^{-7}.

Potential to probe scalar meson properties.

Abstract

The role of the triangle mechanism in the decay process $B_0\to J/\psi K^0f_0 \to J/\psi K^0\pi^+\pi^-$ and $B_0\to J\psi K^0a_0\to J/\psi K^0 \pi^0\eta$ is probed. In these process, the triangle singularity appears from the decay of $B^0$ into $J/\psi\phi K^0$ then $\phi$ decays into $K^0\bar{K^0}$ and $K^0\bar{K^0}$ merged into $f_0$ or $a_0$ which finally decay into $\pi^+\pi^-$ and $\pi^0\eta$ respectively. We find that this mechanism leads to a triangle singularity around $M_{\rm inv}(K^0f_0(a_0))\approx1520\ {\rm MeV}$, and gives sizable branching fractions ${\rm{Br}}(B_0\to J/\psi K^0f_0\to J/\psi K^0\pi^+\pi^-)=1.38\times10^{-6}$ and $ {\rm{Br}}(B_0\to J/\psi K^0a_0\to J/\psi K^0\pi^0\eta)=2.56\times10^{-7}$. This potential investigation can help us obtain the information of the scalar meson $f_0(980)$ or $a_0(980)$.