Measurement of prompt J/ψ pair production in pp collisions at s $$ \sqrt{s} $$ = 7 Tev

Production of prompt J/ meson pairs in proton-proton collisions at s = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 fb -1 . The two J/ mesons are fully reconstructed via their decays into + -pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/ transverse momentum (p T J/ ) and rapidity (|y J/ |):