Accommodating a 650 GeV scalar resonance in HEFT

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 making use of the coupled-channel formalism. Conversely, experimental detection of a resonance may provide interesting information on the couplings and constants of the relevant effective theory. By applying the systematic procedure developed in previous works, we will attempt to accommodate a possible scalar resonance with mass around 650 GeV for which there is preliminary evidence at the LHC in the vector-boson fusion channel. The results are interesting; the resonance can be accommodated within the experimentally allowed range of next-to-leading order coefficients in the Higgs effective field theory but in a rather nontrivial manner. Interestingly, its width and production cross section turn out to agree with the tentative experimental results.