# Probing New Physics by the Tail of the Off-shell Higgs in $V_LV_L$ Mode

## TL;DR

This paper explores how the high-mass tail of off-shell Higgs production, especially in the longitudinal vector boson mode, can be used to detect new physics beyond the Standard Model by analyzing polarization states in $gg o ZZ$ processes.

## Contribution

It introduces a novel approach of using polarization modes in off-shell Higgs processes to probe various new physics scenarios in the Higgs sector.

## Key findings

- Longitudinal mode enhances sensitivity to new physics
- Angular polarization analysis improves detection prospects
- Different Higgs sector modifications produce distinct polarization signatures

## Abstract

Off-shell Higgs at the high mass tail may shed light on the underlying mechanism of the electroweak symmetry breaking. Due to the large cancellation in the standard model (SM) between the box and Higgs-mediated triangle diagrams, the $gg\to WW(ZZ)$ process in the SM is dominated by the $V_T V_T$ transverse-mode at the high mass tail. The cancellation does not necessarily hold, when there is a sufficiently large new physics contribution resulting in $V_LV_L$ longitudinal mode, which is commonly the case when the Higgs sector is modified. Thus the $V_LV_L$ final states in the high mass tail can be utilized as a sensitive probe for such models. In the paper we focus on a study of the $gg \to ZZ$ process in the fully leptonic decay modes, proposing to utilize the polarization modes of the off-shell Higgs to probe new physics, whose contribution mainly shows in the longitudinal mode. As examples, we analyze three different Higgs sector new physics cases (Higgs portal with a light scalar, a broad-width scalar that mixes with the Higgs, and quantum critical Higgs models), and demonstrate that the angular information relating to the polarization serves as very sensitive probe for such new physics.