arXiv subjects

Gustavo G. da Silveira

Publications and source records attributed to Gustavo G. da Silveira.

4 recordsLinked to original sources

arXiv2016

Measuring light-by-light scattering at the LHC and FCC

Elastic light-by-light scattering, $γγ\toγγ$, can be measured in electromagnetic interactions of lead (Pb) ions at the Large Hadron Collider (LHC) and Future Circular Collider (FCC), using the large (quasi)real photon fluxes available in ultraperipheral collisions. The $γγ\toγγ$ cross sections for diphoton masses m$_{γγ}>$ 5 GeV in pp, pPb, and PbPb collisions at LHC ($\sqrt{\rm s_{_{NN}}}$ = 5.5, 8.8, 14 TeV) and FCC ($\sqrt{\rm s_{_{NN}}}$ = 39, 63, 100 TeV) center-of-mass energies are presented. The measurement has controllable backgrounds in PbPb collisions, and one expects about 70 and 2500 signal events per year at the LHC and FCC respectively, after typical detector acceptance and reconstruction efficiency selections.

hep-ph↗

arXiv2016

Observing light-by-light scattering at the Large Hadron Collider

Elastic light-by-light scattering, $γγ\toγγ$, is open to study at the Large Hadron Collider thanks to the large quasi-real photon fluxes available in electromagnetic interactions of protons (p) and lead (Pb) ions. The $γγ\toγγ$ cross sections for diphoton masses $m_{γγ} > 5$ GeV amount to 105 fb, 260 pb, and 370 nb in p-p, p-Pb, and Pb-Pb collisions at nucleon-nucleon center-of-mass energies $\sqrt{s_{NN}}$ = 14 TeV, 8.8 TeV, and 5.5 TeV respectively. Such a measurement has no substantial backgrounds in Pb-Pb collisions where one expects about 70 signal events per run, after typical detector acceptance and reconstruction efficiency selections.

hep-ph↗

arXiv2014

Exclusive production of $W$ pairs in CMS

We report the results on the search for exclusive production of $W$ pairs in the LHC with data collected by the Compact Muon Solenoid detector in proton-proton collisions at $\sqrt{s}$ = 7 TeV. The analysis comprises the two-photon production of a $W$ pairs, ${pp\to p\,W^{+}W^{-}\,p\to p\,νe^{\pm}νμ^{\mp}\,p}$. Two events are observed in data for $p_{\textrm{\footnotesize T}}(\ell)>$ 4 GeV, $|η(\ell)|<$ 2.4 and $m(μ^{\pm}e^{\mp})>$ 20 GeV, in agreement with the standard model prediction of 2.2 $\pm$ 0.4 signal events with 0.84 $\pm$ 0.15 background events. Moreover, a study of the tail of the lepton pair transverse momentum distribution is performed to search for an evidence of anomalous quartic gauge couplings in the $γγ\to W^{+}W^{-}$ vertex. As no events are observed in data, it results in a model-independent upper limits for the anomalous quartic gauge couplings $a^{W}_{0,C}/Λ^{2}$, which are of the order of 10$^{-4}$.

hep-ex↗

arXiv2013

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 $γγ$ production, the exclusive two-photon production of dileptons, $e^{+}e^{-}$ and $μ^{+}μ^{-}$, and the exclusive two-photon production of $W$ pairs in the asymmetric $e^{\pm}μ^{\mp}$ 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 $E_{T}(γ)>$ 5.5 GeV and $|η(γ)|<$ 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 $|η(e)|<$ 2.5, and the cross section for the exclusive dimuon production is set to $σ(pp\to p\,μ^{+}μ^{-}\,p)=3.38^{+0.58}_{-0.55}$ (stat.) $\pm$ 0.16 (syst.) $\pm$ 0.14 (lumi.) pb for $m(μ^{+}μ^{-})>$ 11.5 GeV, $p_{\textrm{T}}(μ)>$ 4 GeV and $|η(μ)|<$ 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 $p_{\textrm{T}}(μ)>$ 4 GeV, $|η(μ)|<$ 2.4 and $m(e^{\pm}μ^{\mp})>$ 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$^{-4}$.

hep-ex↗