First study of the two-body scattering involving charm hadrons

This article presents the first measurement of the interaction between charm hadrons and nucleons. The two-particle momentum correlations of $\mathrm{p}{\mathrm{D}}^{\ensuremath{-}}$ and ${\overline{\mathrm{p}}\mathrm{D}}^{+}$ pairs are measured by the ALICE Collaboration in high-multiplicity pp collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$. The data are compatible with the Coulomb-only interaction hypothesis within $(1.1--1.5)\ensuremath{\sigma}$. The level of agreement slightly improves if an attractive nucleon $(\mathrm{N})\overline{\mathrm{D}}$ strong interaction is considered, in contrast to most model predictions which suggest an overall repulsive interaction. This measurement allows for the first time an estimation of the 68% confidence level interval for the isospin $\mathrm{I}=0$ inverse scattering length of the $\mathrm{N}\overline{\mathrm{D}}$ state ${f}_{0,\mathrm{I}=0}^{\ensuremath{-}1}\ensuremath{\in}[\ensuremath{-}0.4,0.9]\text{ }\text{ }{\mathrm{fm}}^{\ensuremath{-}1}$, assuming negligible interaction for the isospin $\mathrm{I}=1$ channel.