Measurement of prompt J/ψ pair production in pp collisions at √s = 7 Tev

Abstract

Production of prompt J/ψ 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/ψ mesons are fully reconstructed via their decays into μ^+μ^− pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ψ 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/ψ transverse momentum (pT^(J/ψ)) and rapidity (|y^(J/ψ)|): |y^(J/ψ)| < 1.2 for p_T^(J/ψ) > 6.5 GeV/c; 1.2 < |y^(J/ψ)| < 1.43 for a pT threshold that scales linearly with |y^(J/ψ)| from 6.5 to 4.5 GeV/c; and 1.43 < |y^(J/ψ)| < 2.2 for p_T^(J/ψ) > 4.5 GeV/c. The total cross section, assuming unpolarized prompt J/ψ pair production is 1.49 ± 0.07 (stat) ±0.13 (syst) nb. Different assumptions about the J/ψ polarization imply modifications to the cross section ranging from −31% to +27%.

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