Accommodating scalar resonances in the HEFT

TL;DR

This paper discusses how unitarity violations in the Higgs Effective Field Theory (HEFT) can be addressed by introducing scalar resonances through unitarization techniques, aiding in experimental searches and theoretical consistency.

Contribution

It presents a systematic method to incorporate scalar resonances in HEFT using coupled-channel unitarization, linking resonance detection to constraints on effective theory parameters.

Findings

Resonance presence constrains effective couplings.

Absence of predicted resonances rules out certain parameter ranges.

Unphysical resonances indicate incompatible UV completions.

Abstract

Loss of unitarity in an effective field theory is often cured by the appearance of dynamical resonances, revealing the presence of new degrees of freedom. These resonances may manifest themselves when suitable unitarization techniques are implemented in the effective theory, which in the scalar-isoscalar channel require using the coupled-channel formalism. Experimental detection of a resonance would provide precious information on the couplings and constants of the relevant effective theory. Conversely, the absence of a resonance where the unitarized effective theory predicts it should be allows us to rule out a certaing range of couplings that would otherwise be allowed. Likewise, the appearence of unphysical (e.g. acausal) resonances is telling us that no UV completion could give rise to the corresponding couplings in the effective theory. In this talk we summarize the systematical procedure we have implemented in order to confront the effective theory with the absence or presence of resonances in the vector boson fusion channel at the LHC.