Sensitivity to longitudinal vector boson scattering and doubly-charged Higgs boson production in $\mathbf{W^\pm W^\pm jj}$ at future hadron colliders

TL;DR

The paper evaluates the prospects for measuring longitudinal vector boson scattering in same-sign $W^ pm W^ pm jj$ production at future 27, 50, and 100 TeV hadron colliders with 30 ab$^{-1}$, using a tight VBS phase space ($M_{jj}>2$ TeV) and a baseline FCC-hh detector. It employs MadGraph-generated polarized signal samples and SM backgrounds, simulated with a Delphes FCC-hh card, and uses dual BDT frameworks to separate polarization states and distinguish signal from background, followed by profile-likelihood fits to extract $\mu_{LL}$, $\mu_{LT}$, and $\mu_{TT}$. The study quotes projected relative uncertainties on the purely longitudinal component (roughly 22%, 21%, and 15% for 27, 50, and 100 TeV) and translates the results into Georgi-Machacek model constraints on the triplet-sector parameter $s_H$ via doubly charged Higgs production and decay to $W^{\pm}W^{\pm}$, yielding $s_H$ exclusions in the ~0.14–0.25 range at 100 TeV (with systematics) across the explored masses. These results highlight the sensitivity gains from higher collider energy and integrated luminosity for probing EW symmetry breaking and BSM extended Higgs sectors, while noting the omission of NLO EW corrections for WWjj and other detector-specific systematics.

Abstract

We study the sensitivity to longitudinal vector boson scattering at a 27, 50 and 100 TeV $pp$ collider using events containing two leptonically-decaying same-electric-charge $W$ bosons produced in association with two jets. The baseline FCC-hh detector parameterization within the Delphes framework is used under the assumption of fully efficient pile-up mitigation. A tightly constrained phase space with a dijet mass greater than 2 TeV is considered in order to suppress the impact of potential instrumental backgrounds. Based on this setup, the expected sensitivity to the production of longitudinally polarized same-sign $W$ boson pairs is evaluated. Additionally, expected limits are set on doubly charged Higgs bosons produced via vector boson fusion processes and decaying to same-sign $W$ boson pairs.

Figures (4)

• Figure 1: The post-fit distribution of events as a function of $\Delta \phi_{jj}$.
• Figure 2: The post-fit distribution of events as a function of the unrolled BDT (BDTFit3D).
• Figure 3: Post-fit $m_T$ distributions for the 2000 GeV $H^{\pm\pm}_5$ signal at the three FCC-hh center-of-mass energy scenarios; 27 TeV (left), 50 TeV (center) and 100 TeV (right). The bins are optimized to ensure a minimum of 100 background events per bin, resulting in variable bin sizes.
• Figure 4: Expected exclusion limits at $95\%$ CL on $s_H$ (left) and $\sigma(H^{\pm\pm}_5)\times \mathcal{B}(H^{\pm\pm}_5\rightarrow W^{\pm}W^{\pm})$ (right) as a function of $m_{H^{\pm\pm}_5}$ at the three center of mass energy scenarios: 27 TeV (top), 50 TeV (center) and 100 TeV (bottom). The blue solid line indicates exclusion limits with both statistical and systematic uncertainties included whereas the red solid line indicates exclusion limits without systematic uncertainties. The green and yellow bands indicate the $68\%$ and $95\%$ confidence intervals around the median limits, respectively.