Off-shell Higgs Probe to Naturalness

TL;DR

This paper proposes using off-shell Higgs production at the LHC to detect new scalar fields that could address the Higgs naturalness problem, with potential implications for dark matter and baryogenesis.

Contribution

It introduces a novel method to probe scalar singlet extensions of the Standard Model through off-shell Higgs processes at high-energy colliders.

Findings

Potential to detect scalar singlet effects at 5σ at HL-LHC

Enhanced sensitivity at 27 TeV collider

Does not require precise Higgs width measurements

Abstract

Examining the Higgs sector at high energy scales through off-shell Higgs production can potentially shed light on the naturalness problem of the Higgs mass. We propose such a study at the LHC by utilizing a representative model with a new scalar field ($S$) coupled to the Standard Model Higgs doublet ($H$) in a form $ |S|^2 |H|^2$. In the process $p p \rightarrow h^* \rightarrow ZZ$, the dominant momentum-dependent part of the one-loop scalar singlet corrections, especially above the new threshold at $2m_S$, leads to a measurable deviation in the differential distribution of the $Z$-pair invariant mass, in accordance with the quadratic divergence cancellation to the Higgs mass. We find that it is conceivable to probe such new physics at the $5\sigma$ level at the high-luminosity LHC, improving further with the upgraded $27$ TeV LHC, without requiring the precise measurement of the Higgs boson total width. The discovery of such a Higgs portal could also have important implications for thermal dark matter as well as for electroweak baryogenesis.