  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.
