XVIth Quark Confinement and the Hadron Spectrum

Triangle singularity in the J/ψ→ϕπ+a0−(π−η),ϕπ−a0+(π+η) decays

22 Aug 2024, 12:00

30m

M2

Oral B: Light Quarks Light Quarks

Speaker

Wei-Hong Liang

Description

We study the $J/\psi \to \varphi {\pi }^{+}{a}_0(980{)}^{-}(a_0^{-}\to {\pi }^{-}\eta )$ decay, evaluating the double mass distribution in terms of the ${\pi }^{-}\eta$ and ${\pi }^{+}{a}_0^{-}$ invariant masses. We show that the ${\pi }^{-}\eta$ mass distribution exhibits the typical cusp structure of the $a_0(980)$ seen in recent high statistics experiments, and the ${\pi }^{+}{a}_0^{-}$ spectrum shows clearly a peak around $M_{\mathrm{i}\mathrm{n}\mathrm{v}}({\pi }^{+}{a}_0^{-})=1420\mathrm{M}\mathrm{e}\mathrm{V}$, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of ${10}^{-5}$, which is easily accessible in present laboratories. We also call the attention to the fact that the signal obtained is compatible with a bump experimentally observed in the $\eta {\pi }^{+}{\pi }^{-}$ mass distribution in the $J/\psi \to \varphi \eta {\pi }^{+}{\pi }^{-}$ decay and encourage further analysis to extract from there the $\varphi {\pi }^{+}{a}_0^{-}$ and $\varphi {\pi }^{-}{a}_0^{+}$ decay modes.

Presentation materials

TS in Jpsi decay-Liangwh.pdf