2025/08/13 by ALICE Collaboration
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Nuclear Experiment (nucl-ex)
paper · doi:10.48550/arxiv.2508.09867
Direct measurements of the ρ0p interaction have remained so far elusive, with most insights derived indirectly from photoproduction or low-energy partial wave analyses. This letter presents the first direct observation of the ρ0p interaction, obtained through two-particle correlations measured in high-multiplicity, ultrarelativistic proton-proton collisions at √(s) = 13 TeV by the ALICE Collaboration at the LHC. Two-particle correlation data, analyzed within chiral effective field theory (χEFT) using a coupled-channel approach and incorporating recent ϕ-p data, yield a scattering length of aρ0p = (-0.46 ± 0.04) + i(0.20 ± 0.04) fm and constrain coupling strengths of two states identified with the N(1958) and N(1700). These findings emphasize the importance of coupled-channel dynamics and dynamically generated states in understanding the ρ0p interaction. The results establish a vacuum baseline for extrapolation studies to high densities, contributing to the foundation for chiral symmetry restoration searches, and offer collider-based insights into the QCD spectrum, complementing traditional low-energy approaches. This work marks a significant advance in correlation studies, extending the exploration of interactions to the most short-lived QCD states.