Exclusive processes in pp collisions in CMS

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, $|\eta(\mu)|$ 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$^{-4}$.Comment: 7 pages, 6 figures, presented at the XXI International Workshop on Deep-Inelastic Scattering and Related Subjects, April 2013, Marseille, Franc

Diffractive Higgs boson photoproduction in peripheral collisions

An alternative process is proposed for the diffractive Higgs boson production in peripheral $pp$ collisions, exploring it through the photon-proton interaction by Double Pomeron Exchange. It is estimated the event rate of the diffractive Higgs production in central rapidity for Tevatron and LHC energies, being of the order of 1 fb, in agreement to the predictions from other diffractive processes. The results are confronted with those obtained from a similar approach of the Durham group.Comment: 4 pages, 7 figures, contribution to the proceedings of II Latin American Workshop on High Energy Physics [IILAWHEP], 3-7 Dec. 2007, Sao Miguel das Missoes, Brazi

Single and Central Diffractive Higgs Production at the LHC

The single and central diffractive production of the Standard Model Higgs boson is computed using the diffractive factorization formalism, taking into account a parametrization for the Pomeron structure function provided by the H1 Collaboration. We compute the cross sections at NLO accuracy for the gluon fusion process, since it is the leading mechanism for the Higgs boson production. The gap survival probability is also introduced to include the rescattering corrections due to spectator particles present in the interaction. The diffractive ratios are predicted for proton-proton collisions at the LHC, since the beam luminosity is favorable to the Higgs boson detection. These results provide updated estimations for the fraction of single and central diffractive events in the LHC kinematical regime.Comment: To appear in the proceedings of Diffraction 2010: International Workshop on Diffraction in High Energy Physics, Otranto, Italy, 10-15 Sep 201

Local vs. long-range infection in unidimensional epidemics

We study the effects of local and distance interactions in the unidimensional contact process (CP). In the model, each site of a lattice is occupied by an individual, which can be healthy or infected. As in the standard CP, each infected individual spreads the disease to one of its first-neighbors with rate $\lambda$, and with unitary rate, it becomes healthy. However, in our model, an infected individual can transmit the disease to an individual at a distance $\ell$ apart. This step mimics a vector-mediated transmission. We observe the host-host interactions do not alter the critical exponents significantly in comparison to a process with only L\'evy-type interactions. Our results confirm, numerically, early field-theoretic predictions.Comment: 8 pages, 6 figures, to appear on Frontiers in Physic