CMS-BPH-11-021

CMS-BPH-11-021 ; CERN-PH-EP-2014-111
Measurement of prompt J/ $\psi$ pair production in pp collisions at $\sqrt{s}$ = 7 TeV
CMS Collaboration
3 June 2014
J. High Energy Phys. 09 (2014) 094
Abstract: Production of prompt J/ $\psi$ meson pairs in proton-proton collisions at $\sqrt{s}$ = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 inverse-femtobarns. The two J/ $\psi$ mesons are fully reconstructed via their decays into $\mu^+\mu^-$ pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ $\psi$ 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/ $\psi$ transverse momentum ( $p_T^{J/\psi}$ ) and rapidity (\| $y^{J/\psi}$ \|): \| $y^{J/\psi}$ \| lower than 1.2 for $p_T^{J/\psi}$ greater than 6.5 GeV/c; \| $y^{J/\psi}$ \| in [1.2,1.43] for a $p_T$ threshold that scales linearly with \| $y^{J/\psi}$ \| from 6.5 to 4.5 GeV/c; and \| $y^{J/\psi}$ \| in [1.43,2.2] for $p_T^{J/\psi}$ greater than 4.5 GeV/c. The total cross section, assuming unpolarized prompt J/ $\psi$ pair production is 1.49 $\pm$ 0.07 (stat.) $\pm$ 0.13 (syst.) nb. Different assumptions about the J/ $\psi$ polarization imply modifications to the cross section ranging from -31% to +27%.
Links: e-print arXiv:1406.0484 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; Public twiki page ; HepData record ; CADI line (restricted) ;

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