Searching for New Heavy Neutral Gauge Bosons using Vector Boson Fusion Processes at the LHC

TL;DR

This study explores the potential of vector boson fusion processes at the LHC to discover or exclude new heavy neutral gauge bosons, specifically Z' bosons, by analyzing dilepton decay channels and VBF topology to improve detection sensitivity.

Contribution

It introduces a novel approach using VBF processes and dilepton channels to search for Z' bosons, extending the discovery reach beyond traditional methods at the LHC.

Findings

Expected exclusion bounds up to 1.8-2.5 TeV for Z' masses.

Discovery potential with significances over 5σ for Z' masses up to 1.6-2.2 TeV.

Effective background reduction using VBF topology and dilepton signatures.

Abstract

New massive resonances are predicted in many extensions to the Standard Model (SM) of particle physics and constitutes one of the most promising searches for new physics at the LHC. We present a feasibility study to search for new heavy neutral gauge bosons using vector boson fusion (VBF) processes, which become especially important as the LHC probes higher collision energies. In particular, we consider the possibility that the discovery of a $Z'$ boson may have eluded searches at the LHC. The coupling of the $Z'$ boson to the SM quarks can be small, and thus the $Z'$ would not be discoverable by the searches conducted thus far. In the context of a simplified phenomenological approach, we consider the $Z'\to\tau\tau$ and $Z'\to\mu\mu$ decay modes to show that the requirement of a dilepton pair combined with two high $p_{T}$ forward jets with large separation in pseudorapidity and with large dijet mass is effective in reducing SM backgrounds. The expected exclusion bounds (at 95\% confidence level) are $m(Z') < 1.8$ TeV and $m(Z') < 2.5$ TeV in the $\tau\tau j_{f}j_{f}$ and $\mu\mu j_{f}j_{f}$ channels, respectively, assuming 1000 fb$^{-1}$ of 13 TeV data from the LHC. The use of the VBF topology to search for massive neutral gauge bosons provides a discovery reach with expected significances greater than 5$\sigma$ (3$\sigma$) for $Z'$ masses up to 1.4 (1.6) TeV and 2.0 (2.2) TeV in the $\tau\tau j_{f}j_{f}$ and $\mu\mu j_{f}j_{f}$ channels.