Comunicazione

Recent CMS results in the search of new signals in quarkonium physics.

Di Florio A.
  Lunedì 11/09   14:30 - 18:30   Aula A208   I - Fisica nucleare e subnucleare
Two recents results by the CMS Collaboration in the quarkonium field, exploiting proton-proton collisions at $\sqrt{s} = 8$ TeV, are discussed. The first observation of $Y(1S)$ pair production has been performed with both quarkonia fully reconstructed from $\mu^{+} \mu^{-}$ pairs. 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 evidence for an unexpected narrow $B_{s} \pi$ structure claimed by the D0 Collaboration and named $X(5568)$ has triggered its search in other hadron collider experiments. The CMS search provides the current most stringent Upper Limits on the ratio of the production rates of $X(5568)$ and $B_{s}$ multiplied by the unknown branching fraction of the $B_{s} \pi$ decay, given in two different kinematic regions defined on the basis of the transverse momentum of the $B_{s}$. The obtained upper limits contradict the D0 measurement and are in agreement with the results by the LHCb Collaboration.