Exclusive processes in pp collisions in CMS

Abstract

We report the results on the searches of exclusive production of low- and high-mass pairs with the Compact Muon Solenoid (CMS) detector in proton-proton collisions at $\sqrt{s}$ = 7 TeV. The analyses comprise the central exclusive $\gamma\gamma$ production, the exclusive two-photon production of dileptons, $e^{+}e^{-}$ and $\mu^{+}\mu^{-}$, and the exclusive two-photon production of $W$ pairs in the asymmetric $e^{\pm}\mu^{\mp}$ decay channel. No diphotons candidates are observed in data and an upper limit on the cross section is set to 1.18 pb with 95% confidence level for $E_{T}(\gamma)>$ 5.5 GeV and $|\eta(\gamma)|<$ 2.5. In the measurement of exclusive dilepton production, seventeen $e^{+}e^{-}$ candidates are observed in data with $E_{T}(e)>$ 5.5 GeV and $|\eta(e)|<$ 2.5, and the cross section for the exclusive dimuon production is set to $\sigma(pp\to p\,\mu^{+}\mu^{-}\,p)=3.38^{+0.58}_{-0.55}$ (stat.) $\pm$ 0.16 (syst.) $\pm$ 0.14 (lumi.) pb for $m(\mu^{+}\mu^{-})>$ 11.5 GeV, $p_{\textrm{T}}(\mu)>$ 4 GeV and $|\eta(\mu)|<$ 2.1, both in agreement with the theoretical predictions. For high-mass systems, two events are observed in data for the exclusive two-photon production of $W$ pairs for $p_{\textrm{T}}(\mu)>$ 4 GeV, $|\eta(\mu)|<$ 2.4 and $m(e^{\pm}\mu^{\mp})>$ 20 GeV. Moreover, the study of the tail of the dilepton transverse momentum distribution resulted in model-independent upper limits for the anomalous quartic gauge couplings, which are of the order of 10$^{-4}$.