Abstract

This Letter presents a search for new resonances decaying to final states with a vector boson produced in association with a high transverse momentum photon, Vγ, with V=W(→ℓν) or Z(→ℓ+ℓ−), where ℓ=e or μ. The measurements use 20.3 fb−1 of proton–proton collision data at a center-of-mass energy of s=8 TeV recorded with the ATLAS detector. No deviations from the Standard Model expectations are found, and production cross section limits are set at 95% confidence level. Masses of the hypothetical aT and ωT states of a benchmark Low Scale Technicolor model are excluded in the ranges [275,960] GeV and [200,700]∪[750,890] GeV, respectively. Limits at 95% confidence level on the production cross section of a singlet scalar resonance decaying to Zγ final states have also been obtained for masses below 1180 GeV.

Highlights

  • The search for diboson resonances is an essential step in exploring the source of Electroweak Symmetry Breaking (EWSB)

  • The Low Scale Technicolor (LSTC) [5] model is used as a benchmark model for the search for spin-1 resonances decaying to W γ and Z γ final states explored in this paper

  • The ATLAS detector [12] is composed of an inner tracker detector (ID) surrounded by a thin superconducting solenoid providing a 2 T axial magnetic field, electromagnetic (EM) and hadronic calorimeters (HC), and a muon spectrometer (MS) immersed in the magnetic field produced by a system of superconducting toroids

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Summary

Introduction

The search for diboson resonances is an essential step in exploring the source of Electroweak Symmetry Breaking (EWSB). This Letter presents a search for narrow scalar and vector heavy resonances decaying to W γ or Z γ final states, where the W and Z bosons decay to leptons (e or μ). The Low Scale Technicolor (LSTC) [5] model is used as a benchmark model for the search for spin-1 resonances decaying to W γ and Z γ final states explored in this paper. A phenomenological model describing a singlet scalar particle φ [7,8] is chosen as another benchmark in the search for spin-0 resonances decaying to Z γ. The neutral scalar could be composite, produced by a hypothetical new strong interaction It could be the pseudo-Goldstone boson playing an important role in the dynamical EWSB. Collaboration, excluding the production of ρT for masses below mρT < 1.14 TeV, but using a slightly different choice of parameters

ATLAS detector and data sample
Signal and background simulated samples
Physics object reconstruction and selection
A Z -veto requirement is applied in the electron channel of the
Analysis strategy
Study of the background composition
Fit model and statistical methods
Background modeling
Signal modeling
Statistical method
Systematic uncertainties
Results
10. Conclusions
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