The interaction of Lambda and Sigma hyperons (Y) with nucleons (N) is strongly influenced by the coupled-channel dynamics. Due to the small mass difference of the NLambda and NSigma systems, the sizable coupling strength of the NSigma ↔ NLambda processes constitutes a crucial element in the determination of the NLambda interaction. In this letter we present the most precise measurements on the interaction of pLambda pairs, from zero relative momentum up to the opening of the NSigma channel. The correlation function in the relative momentum space for pLambda ⊕ p_bar Lambda_bar pairs measured in high-multiplicity triggered pp collisions at √s = 13 TeV at the LHC is reported. The opening of the inelastic NSigma channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum k∗ = 289 MeV/c. This represents the first direct experimental observation of the NSigma ↔ NLambda coupled channel in the pLambda system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the NSigma ↔ NLambda transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NNLambda interaction for a proper description of the Lambda in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars.

Exploring the NLambda-NSigma coupled system with high precision correlation techniques at the LHC

P. Cortese;L. Ramello;M. Sitta;
2022-01-01

Abstract

The interaction of Lambda and Sigma hyperons (Y) with nucleons (N) is strongly influenced by the coupled-channel dynamics. Due to the small mass difference of the NLambda and NSigma systems, the sizable coupling strength of the NSigma ↔ NLambda processes constitutes a crucial element in the determination of the NLambda interaction. In this letter we present the most precise measurements on the interaction of pLambda pairs, from zero relative momentum up to the opening of the NSigma channel. The correlation function in the relative momentum space for pLambda ⊕ p_bar Lambda_bar pairs measured in high-multiplicity triggered pp collisions at √s = 13 TeV at the LHC is reported. The opening of the inelastic NSigma channels is visible in the extracted correlation function as a cusp-like structure occurring at relative momentum k∗ = 289 MeV/c. This represents the first direct experimental observation of the NSigma ↔ NLambda coupled channel in the pLambda system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the NSigma ↔ NLambda transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NNLambda interaction for a proper description of the Lambda in-medium properties, which has implications on the nuclear equation of state and for the presence of hyperons inside neutron stars.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11579/145880
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