Speaker
Description
Using large data samples of di-muon events, CMS has performed detailed measurements in the field of double quarkonium production. In the double quarkonium final states potential resonances, such as heavy quark tetra-quarks governed by strong interaction, have been predicted. The first observation of Y(1S) pair production has been recently performed, with both quarkonia fully reconstructed from oppositely charged muon pairs, by exploiting proton-proton collisions at sqrt(s) = 8 TeV. A fiducial cross section of the Y(1S) pair production is provided within the single-Y acceptance |rapidity(Y)|<2. An effective cross-section is also estimated on the basis of the fiducial cross-section and the fraction of DPS contribution. The study of J/psi pair final state produced in proton-proton collisions at sqrt(s) = 7 TeV is foreseen to be extended to a center-of-mass of 8TeV providing the total and differential cross sections measured in a phase space defined by the individual J/psi transverse momentum and rapidity. These observations allow us to access, for the first time, to the high-transverse-momentum region of J/psi pair production where model predictions are not yet established. The first cross section complementary measurements in CMS and LHCb allowed to set up production models that not only include single-parton scattering but also double-parton scattering and consider color singlet and color octet intermediate J/psi states. Indeed it is a crucial step to isolate double quarkonium signals by understanding the non-resonant pair production.
