Observation of triple J/ψ meson production in proton-proton collisions

Protons consist of three valence quarks, two up-quarks and one down-quark, held together by gluons a sea quark-antiquark pairs. Collectively, quarks are referred to as partons. In proton-proton collision, typically only parton each proton undergoes hard scattering - single-parton leaving the remainder slightly disturbed. Here, we report study double- triple-parton scatterings through simultaneous production J/$\psi$ mesons, which charm pair, in collisions recorded with CMS experiment at Large Hadron Collider. We observed this process reconstructed decays mesons into pairs oppositely charged muons statistical significance above five standard deviations. measured inclusive fiducial cross section be 272 $^{+141}_{-104}$ (stat) $\pm$ 17 (syst) fb, compared it theoretical expectations for triple-J/$\psi$ meson single-, scenarios. Assuming factorization multiple hard-scattering probabilities terms sections, dominant contributions process.