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

Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Dragicevic, M. and Ero, J. and Fabjan, C. and Friedl, M. and Fruhwirth, R. and Ghete, V. M. and Hartl, C. and Hormann, N. and Hrubec, J. and Jeitler, M. and Kiesenhofer, W. and Knunz, V. and Krammer, M. and Kratschmer, I. and Liko, D. and Mikulec, I. and Rabady, D. and Rahbaran, B. and Rohringer, H. and Schofbeck, R. and Strauss, J. and Taurok, A. and Treberer-Treberspurg, W. and Waltenberger, W. and Wulz, C. E. and Filipovic, Nicolas and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Béni, Noémi Tekla and Karancsi, János and Molnár, József and Pálinkás, József and Szillási, Zoltán and Raics, Péter and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2014) Measurement of prompt J/ψ pair production in pp collisions at √ s = 7 TeV. JOURNAL OF HIGH ENERGY PHYSICS (9). ISSN 1126-6708

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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 (p J/ψ T ) and rapidity (|y J/ψ |): |y J/ψ | < 1.2 for p J/ψ T > 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 J/ψ T > 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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