Abstract
The production of electroweak bosons is an important part the Standard Model and it can also shed a light on new physics, in the form of anomalous gauge couplings. This poster presents the study of exclusive or quasi-exclusive γ γ → W +W − production. The measurement of the process pp → p(∗) +W+W− + p(∗) → p(∗) +e±μ∓ + p(∗) used an integrated luminosity of 19.7fb−1 of 8TeV proton-proton collisions at the LHC. Events are selected by requiring the presence of an electron-muon pair with large transverse momentum pT(μ±e∓) > 30GeV, and no associated charged particles detected from the same vertex. With this analysis the CMS Collaboration has set upper limits on the values of anomalous quartic gauge coupling coefficients for both dimension-6 and dimension-8 effective field theory operators, giving the most stringent limits to date.
Highlights
Any deviation from the Standard Model (SM) may be quantifiable via anomalous quartic gauge couplings of effective field theory (EFT) operators of dimension-6 [1]
One alternative to regulate the rising of the cross section at high energies is to multiply the aW0,C parameters by a dipole form factor (FF) as in eq 1.3, where Sγγ is the energy exchange in the diphoton vertex
The observed yields and kinematic distributions are consistent with the SM prediction, with a combined significance over the background-only hypothesis of 3.4σ
Summary
SU(2) ⊗ U(1) symmetry of the SM is possible, making dimension-8 the lowest-order operators where new physics can cause deviations in the purely quartic gauge boson couplings. In this formalism fourteen operators contribute to γ couplings, which could generate a WW Zγ vertex. One alternative to regulate the rising of the cross section at high energies is to multiply the aW0,C parameters by a dipole form factor (FF) as in eq 1.3, where Sγγ is the energy exchange in the diphoton vertex The results in this analysis are studied either using a cutoff energy scale Λcutoff = 500 GeV or with no cutoff ( violating unitarity). Trigger and Preselection m(μ±e∓) > 20 GeV Muon and electron identification μ±e∓ vertex with no add. tracks pT(μ±e∓) > 30 GeV
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