Measurement of $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }\eta$ from 3.5106 to 4.6988 GeV and study of $\Lambda \bar{\Lambda }$ mass threshold enhancement

Abstract

Using data samples with a total integrated luminosity of approximately 18 fb${}^{-1}$ collected by the BESIII detector operating at the BEPCII, the process $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }\eta$ is studied at center-of-mass energies between 3.5106 and 4.6988 GeV. The Born cross section for the process $e^{+}{e}^{-}\to \Lambda \bar{\Lambda }\eta$ is measured. No significant structure is observed in the Born cross section line shape. An enhancement near the $\Lambda \bar{\Lambda }$ mass threshold is observed for the first time in the process. The structure can be described by an $S$-wave Breit-Wigner function. Neglecting contribution of excited $\Lambda$ states and potential interferences, the mass and width are determined to be ($2356\pm 7\pm 17$) MeV/$c^2$ and ($304\pm 28\pm 54$) MeV, respectively, where the first uncertainties are statistical and the second are systematic.

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• The fully-light vector tetraquark states with explicit P-wave via the QCD sum rules
• Baryons and baryoniums in the perspective of QCD sum rules