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 N Lambda and N Sigma systems, the sizable coupling strength of the N Sigma <-> N Lambda processes constitutes a crucial element in the determination of the N Lambda interaction. In this letter we present the most precise measurements on the interaction of p Lambda pairs, from zero relative momentum up to the opening of the N Sigma channel. The correlation function in the relative momentum space for p Lambda circle plus (p) over bar(Lambda) over bar pairs measured in high-multiplicity triggered pp collisions at root s = 13 TeV at the LHC is reported. The opening of the inelastic N Sigma 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 N Sigma <-> N Lambda coupled channel in the p Lambda system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the N Sigma <-> N Lambda transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NN Lambda 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 N Lambda-N Lambda coupled system with high precision correlation techniques at the LHC

M. D. Buckland;P. Camerini;G. Contin;C. De Martin;M. Faggin;E. Fragiacomo;G. Luparello;G. V. Margagliotti;S. Piano;R. Rui;V. Zaccolo;
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 N Lambda and N Sigma systems, the sizable coupling strength of the N Sigma <-> N Lambda processes constitutes a crucial element in the determination of the N Lambda interaction. In this letter we present the most precise measurements on the interaction of p Lambda pairs, from zero relative momentum up to the opening of the N Sigma channel. The correlation function in the relative momentum space for p Lambda circle plus (p) over bar(Lambda) over bar pairs measured in high-multiplicity triggered pp collisions at root s = 13 TeV at the LHC is reported. The opening of the inelastic N Sigma 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 N Sigma <-> N Lambda coupled channel in the p Lambda system. The correlation function is compared with recent chiral effective field theory calculations, based on different strengths of the N Sigma <-> N Lambda transition potential. A weaker coupling, as possibly supported by the present measurement, would require a more repulsive three-body NN Lambda 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.
2022
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https://www.sciencedirect.com/science/article/pii/S0370269322004063
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/3038600
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