Curing tachyonic tree-level syndrome in NMSSM light-singlet scenarios

TL;DR

This paper addresses the issue of tachyonic instabilities in the Higgs sector of the NMSSM by demonstrating how to properly include loop corrections, ensuring consistent Higgs mass predictions and decay properties.

Contribution

It introduces a method to handle tachyonic tree-level masses in the NMSSM by incorporating loop corrections, improving the accuracy of Higgs spectrum calculations.

Findings

Loop corrections stabilize the Higgs spectrum.

Method allows consistent Higgs decay width calculations.

Reduces theoretical uncertainties in Higgs mass predictions.

Abstract

Models with an extended Higgs sector open up the phenomenological possibility of additional scalars, beyond the SM-like boson observed by the LHC, with mass at or below the electroweak scale. Such scenarios are in particular viable in the presence of electroweak-singlet spin-0 fields, as expected for instance in the context of the NMSSM. Given that the size of radiative corrections can substantially affect the Higgs potential, a negative squared mass at the tree level does not necessarily yield a tachyonic spectrum at the physical level, but only indicates a failure of the tree-level description for calculational purposes. We explain how to tackle this technical issue in the example of the NMSSM, in scenarios with light CP-odd or CP-even singlet-dominated states and show how loop corrections to the Higgs masses and decay widths can be derived with the regularized Lagrangian. We further explore how the same flexibility in the definition of tree-level parameters can be exploited to circumvent large deviations of the tree-level spectrum from the kinematical setup in Higgs decays, or to estimate the theoretical uncertainty associated with the discrepancy between tree-level and physical Higgs spectra. The latter is of particular relevance for the properties of the SM-like Higgs boson in supersymmetry-inspired models.