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

2024/02/27 by Xiao, C. W., Dias, J. M., Dai, L. R. +2
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)

paper · doi:10.48550/arxiv.2402.17584

Abstract

We study the J/ψ→ ϕπ⁺ a₀(980)^- (a₀^- → π^- η) decay, evaluating the double mass distribution in terms of the π^- η and π⁺ a^-₀ invariant masses. We show that the π^- η mass distribution exhibits the typical cusp structure of the a₀(980) seen in recent high statistics experiments, and the π⁺ a^-₀ spectrum shows clearly a peak around M_{\rm inv}(π⁺ a^-₀)=1420 \rm MeV, 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 attention to the fact that the signal obtained is compatible with a bump experimentally observed in the ηπ⁺π^- mass distribution in the J/ψ→ ϕηπ⁺π^- decay and encourage further analysis to extract from there the ϕπ⁺ a₀^- and ϕπ^- a₀⁺ decay modes.

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