Visible narrow cusp structure in ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ enhanced by triangle singularity

Abstract

A resonance-like structure as narrow as 10 MeV is observed in the $K^{-}p$ invariant mass distributions in ${\Lambda }_c^{+}\to p{K}^{-}{\pi }^{+}$ at Belle. Based on the large data sample of about 1.5 million events and the small bin width of just 1 MeV for the $K^{-}p$ invariant mass spectrum, the narrow peak is found precisely lying at the $\Lambda \eta$ threshold. While lacking evidence for a quark model state with such a narrow width at this mass region, we find that this narrow structure can be naturally identified as a threshold cusp but enhanced by the nearby triangle singularity via the $\Lambda$-$a_0(980{)}^{+}$ or $\eta$-$\Sigma (1660{)}^{+}$ rescatterings.

6 pages, 4 figures

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• Photoproduction of hidden-bottom pentaquark and related topics
• Theoretical study of the $\Omega (2012)$ state in the ${\Omega }_c^0\to {\pi }^{+}\Omega (2012{)}^{-}\to {\pi }^{+}(\bar{K}\Xi {)}^{-}$ and ${\pi }^{+}(\bar{K}\Xi \pi {)}^{-}$ decays
• Threshold effects as the origin of $Z_{cs}(4000)$, $Z_{cs}(4220)$ and $X(4700)$ observed in $B^{+}\to J/\psi \varphi K^{+}$
• Possibility of $T_{c\bar{s}}(2900)$ as the resonance-like structure induced by threshold effects
• The $a_0(980)$ in the single Cabibbo-suppressed process ${\Lambda }_c\to {\pi }^0\eta p$
• Cabibbo-favored ${\Lambda }_c^{+}\to \Lambda a_0(980{)}^{+}$ decay in the final state interaction
• Radiative decays of $f_1(1285)$ as the $K^{\ast }\bar{K}$ molecular state
• Production of hidden-charm and hidden-bottom pentaquark states in electron-proton collisions
• Detecting the pure triangle sigularity effect through the $\psi (2S)\to p\bar{p}\eta /p\bar{p}{\pi }^0$ process
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• Evasion of HSR in the charmless decays of excited $P$-wave charmonia
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• Studying ${\Lambda }^{\ast }$ resonances in the $p\bar{p}\to \Lambda \bar{\Lambda }\eta$ reaction
• Box Singularity Conditions in Box Diagrams of Decay Processes
• Proposal to detect a moving triangle singularity in $\psi (2S)\to {\pi }^{+}{\pi }^{-}{K}^{+}{K}^{-}$ process