p p -> j j e+/- mu+/- nu nu and j j e+/- mu-/+ nu nu at O(α_{em}^6) and O(α_{em}^4 α_s^2) for the Study of the Quartic Electroweak Gauge Boson Vertex at LHC

TL;DR

This work investigates how the LHC can probe genuine quartic electroweak gauge-boson couplings through weak-boson fusion in $pp\to jj W^+W^-$ and $pp\to jj W^\pm W^\pm$, performing a complete partonic-level calculation at ${\cal O}(\alpha_{em}^6)$ and ${\cal O}(\alpha_{em}^4 \alpha_s^2)$ with full interference and realistic backgrounds. It develops a model-independent EFT framework for quartic vertices under both linear (dimension-8) and nonlinear (chiral) realizations of EW symmetry breaking, linking linear coefficients $f_{0,1}$ to $\Delta c^{VV'}_i$ and nonlinear parameters $\alpha_4$, $\alpha_5$ to the same shifts. The analysis advocates a data-driven background estimation strategy and a comprehensive set of forward-jet tagging and central-jet veto cuts, showing that the LHC can improve current indirect bounds by more than an order of magnitude and can test scenarios without a light Higgs boson. Overall, the work demonstrates a viable path to precision probes of the electroweak symmetry-breaking sector at the LHC using WBF processes and EFT parameterizations, with implications for identifying new physics at higher scales.

Abstract

We analyze the potential of the CERN Large Hadron Collider (LHC) to study the structure of quartic vector-boson interactions through the pair production of electroweak gauge bosons via weak boson fusion q q -> q q W W. In order to study these couplings we have performed a partonic level calculation of all processes p p -> j j e+/- mu+/- nu nu and pp -> j j e+/- mu-/+ nu nu at the LHC using the exact matrix elements at O(α_{em}^6) and O(α_{em}^4 α_s^2) as well as a full simulation of the t tbar plus 0 to 2 jets backgrounds. A complete calculation of the scattering amplitudes is necessary not only for a correct description of the process but also to preserve all correlations between the final state particles which can be used to enhance the signal. Our analyses indicate that the LHC can improve by more than one order of magnitude the bounds arising at present from indirect measurements.

Figures (8)

• Figure 1: Normalized distribution of the transverse momentum of the charge leptons for $t\bar{t}$ (red solid line), $t \bar{t}j$ (blue dashed line), $t \bar{t}jj$ (black dot-dashed line), SM irreducible production (magenta dotted line), and anomalous $W^+ W^-$ contribution $\sigma_{00}$ (blue solid line marked "ano"). We assumed $m_h=120$ GeV and applied cuts (\ref{['cuts1']})--(\ref{['cut:rap']}) but for with a relaxed cut $p_T^\ell>20$ GeV.
• Figure 2: Normalized jet-jet invariant mass distribution for $t\bar{t}$ (red solid line), $t \bar{t}j$ (blue dashed line), $t \bar{t}jj$ (black dot-dashed line), SM irreducible production (magenta dotted line), and anomalous $W^+ W^-$ contribution $\sigma_{00}$ (blue solid line marked "ano"). We assumed $m_h=120$ GeV and applied cuts (\ref{['cuts1']})--(\ref{['cut:rap']}).
• Figure 3: Normalized distribution of the $e\mu$ azimuthal angle difference for $t \bar{t}j$ (dashed line), irreducible background (dotted line), and anomalous $W^+ W^-$ production (solid line). We assumed $m_h=120$ GeV and applied cuts (\ref{['cuts1']})--(\ref{['c:veto']}).
• Figure 4: Normalized distribution of $M_T^{WW}$ for $t \bar{t}j$ (dashed line), irreducible background (dotted line), and anomalous $W^+ W^-$ production (solid line). We assumed $m_h=120$ GeV and applied cuts (\ref{['cuts1']})--(\ref{['c:phi']}).
• Figure 5: Normalized lepton transverse momentum distribution for IRED$++$ background (solid line), IRED$--$ background (dashed line), $W^+W^+$$\sigma_{00}$ (dot-dashed line), and $W^- W^-$$\sigma_{00}$ (dotted line). We assumed $m_h=120$ GeV and applied cuts (\ref{['cuts1']})--(\ref{['cut:rap']}).