Quantum interference among heavy NMSSM Higgs bosons

TL;DR

This paper investigates quantum interference effects among nearly degenerate heavy Higgs bosons in the NMSSM at the LHC, revealing significant impacts on inclusive cross sections that are not observable in differential distributions due to detector resolution limits.

Contribution

It introduces a full Higgs propagator matrix approach to accurately account for interference effects among nearly degenerate Higgs states in the NMSSM at the LHC.

Findings

Interference effects significantly alter inclusive cross sections.

Differential distributions are not sensitive to interference effects.

Quantitative analysis for benchmark points shows measurable impact on predictions.

Abstract

In the Next-to-Minimal Supersymmetric Standard Model (NMSSM), it is possible to have strong mass degeneracies between the new singlet-like scalar and the heavy doublet-like scalar, as well as between the singlet-like and doublet-like pseudoscalar Higgs states. When the difference in the masses of such states is comparable with the sum of their widths, the quantum mechanical interference between their propagators can become significant. We study these effects by taking into account the full Higgs boson propagator matrix in the calculation of the production process of $\tau^+\tau^-$ pairs in gluon fusion at the Large Hadron Collider (LHC). We find that, while these interference effects are sizeable, they are not resolvable in terms of the distributions of differential cross sections, owing to the poor detector resolution of the $\tau^+\tau^-$ invariant mass. They are, however, identifiable via the inclusive cross sections, which are subject to significant variations with respect to the standard approaches, wherein the propagating Higgs bosons are treated independently from one another. We quantify these effects for several representative benchmark points, extracted from a large set of points, obtained by numerical scanning of the NMSSM parameter space, that satisfy the most important experimental constraints currently available.