Study of double J∕ψ production mechanisms at COMPASS

Abstract

During the past 40 years, the production of pairs of [Formula: see text] mesons in high-energy hadron collisions has been studied by several experiments. Despite the experimental and theoretical efforts, the origin of the process and the relative weight of different production mechanisms remain unknown. Depending on the energy scale, the double [Formula: see text] production can be described by single- and/or double-parton scattering sub-processes and gluon–gluon fusion or quark–antiquark annihilation mechanisms. The process can also be related to the hypothesis of the intrinsic charm of hadrons and the existence of exotic tetraquark states which were predicted by various theoretical models and have recently been observed by the LHCb experiment. To study dimuon pair production, the COMPASS experiment at CERN uses a 190[Formula: see text]GeV/[Formula: see text] negative pion beam impinging on different nuclear targets. First preliminary COMPASS results on [Formula: see text] pair production will be presented. The search for possible signals from exotic resonances and the study of double [Formula: see text] production mechanisms will be discussed.