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

Three-body nuclear forces play an important role in the structure of nuclei and hypernuclei and are also incor- porated in models to describe the dynamics of dense baryonic matter, such as in neutron stars. So far, only indirect mea- surements 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 car- ried out for pp collisions at √s = 13 TeV. Three-particle cumulants are extracted from the correlation functions by applying the Kubo formalism, where the three-particle inter- action contribution to these correlations can be isolated after subtracting the known two-body interaction terms. A nega- tive 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 demon- strates the accessibility of three-baryon correlations at the LHC.