Towards the understanding of the genuine three-body interaction for p$-$p$-$p and p$-$p$-\Lambda$

TL;DR

This paper reports the first direct measurement of three-baryon interactions in proton-proton and proton-Lambda systems at the LHC, revealing residual three-body effects in proton systems and providing new insights into nuclear forces.

Contribution

It introduces a novel experimental approach to directly measure three-body nuclear forces using three-particle correlation functions in high-energy collisions.

Findings

Negative three-particle cumulant for p-p-p suggests residual three-body effects.

p-p-Lambda cumulant is consistent with zero, indicating no significant three-body interaction.

Demonstrates the feasibility of studying three-baryon correlations at the LHC.

Abstract

Three-body nuclear forces play an important role in the structure of nuclei and hypernuclei and are also incorporated in models to describe the dynamics of dense baryonic matter, such as in neutron stars. So far, only indirect measurements anchored to the binding energies of nuclei can be used to constrain the three-nucleon force, and if hyperons are considered, the scarce data on hypernuclei impose only weak constraints on the three-body forces. In this work, we present the first direct measurement of the p$-$p$-$p and p$-$p$-\Lambda$ systems in terms of three-particle correlation functions carried out for pp collisions at $\sqrt{s} = 13$ TeV. Three-particle cumulants are extracted from the correlation functions by applying the Kubo formalism, where the three-particle interaction contribution to these correlations can be isolated after subtracting the known two-body interaction terms. A negative cumulant is found for the p$-$p$-$p system, hinting to the presence of a residual three-body effect while for p$-$p$-\Lambda$ the cumulant is consistent with zero. This measurement demonstrates the accessibility of three-baryon correlations at the LHC.