Observation of J/ψ-pair production in pp collisions at s=7 TeV

Abstract

The production of J/ψpairs in proton–proton collisions at a centre-of-mass energy of 7 TeV has beenobserved using an integrated luminosity of 37.5 pb−1collected with the LHCb detector. The productioncross-section for pairs with both J/ψin the rapidity range 2<yJ/ψ<4.5 and transverse momentumpJ/ψT<10 GeV/cisσJ/ψJ/ψ=5.1±1.0±1.1nb,where the first uncertainty is statistical and the second systematic.