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 pD− and pD¯ þ pairs are measured by the ALICE Collaboration in high-multiplicity pp collisions at ffiffi s p ¼ 13 TeV. The data are compatible with the Coulomb-only interaction hypothesis within ð1.1–1.5Þσ. The level of agreement slightly improves if an attractive nucleon ðNÞD 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 I ¼ 0 inverse scattering length of the ND state ¯ f−1 0;I¼0 ∈ ½−0.4; 0.9 fm−1, assuming negligible interaction for the isospin I ¼ 1 channel.