  Deuterons are atomic nuclei composed of a neutron and a proton held together
by the strong interaction. Unbound ensembles composed of a deuteron and a third
nucleon have been investigated in the past using scattering experiments and
they constitute a fundamental reference in nuclear physics to constrain nuclear
interactions and the properties of nuclei. In this work K$^{+}-$d and p$-$d
femtoscopic correlations measured by the ALICE Collaboration in proton$-$proton
(pp) collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are
presented. It is demonstrated that correlations in momentum space between
deuterons and kaons or protons allow us to study three-hadron systems at
distances comparable with the proton radius. The analysis of the K$^{+}-$d
correlation shows that the relative distances at which deuterons and
proton/kaons are produced are around 2 fm. The analysis of the p$-$d
correlation shows that only a full three-body calculation that accounts for the
internal structure of the deuteron can explain the data. In particular, the
sensitivity of the observable to the short-range part of the interaction is
demonstrated. These results indicate that correlations involving light nuclei
in pp collisions at the LHC will also provide access to any three-body systems
in the strange and charm sectors.

Nuclear Experiment;High Energy Physics - Experiment