Tumasyan, A.Adam, W.Andrejkovic, J. W.Bergauer, T.Chatterjee, S.Damanakis, K.Dragicevic, M.2025-03-232025-03-2320231745-24731745-2481https://doi.org/10.1038/s41567-022-01838-yhttps://hdl.handle.net/11486/5931Protons consist of three valence quarks, two up-quarks and one down-quark, held together by gluons and a sea of quark-antiquark pairs. Collectively, quarks and gluons are referred to as partons. In a proton-proton collision, typically only one parton of each proton undergoes a hard scattering - referred to as single-parton scattering - leaving the remainder of each proton only slightly disturbed. Here, we report the study of double- and triple-parton scatterings through the simultaneous production of three J/psi mesons, which consist of a charm quark-antiquark pair, in proton-proton collisions recorded with the CMS experiment at the Large Hadron Collider. We observed this process - reconstructed through the decays of J/psi mesons into pairs of oppositely charged muons - with a statistical significance above five standard deviations. We measured the inclusive fiducial cross-section to be 272(-104)(+141) (stat) +/- 17 (syst) fb, and compared it to theoretical expectations for triple-J/psi meson production in single-, double- and triple-parton scattering scenarios. Assuming factorization of multiple hard-scattering probabilities in terms of single-parton scattering cross-sections, double- and triple-parton scattering are the dominant contributions for the measured process.eninfo:eu-repo/semantics/openAccessDouble Parton InteractionsP(P)Over-Bar CollisionsMatrix-ElementJet EventsHelac-OniaScatteringsGeneratorPpArticle10.1038/s41567-022-01838-y2-s2.0-85162051065Q1WOS:000927936700008Q1