The NMSSM Solution to the Fine-Tuning Problem, Precision Electroweak Constraints and the Largest LEP Higgs Event Excess

TL;DR

The paper demonstrates how the NMSSM naturally avoids fine-tuning in electroweak symmetry breaking for a light Higgs near 100 GeV, consistent with precision data and LEP excess, through specific decay channels and parameter correlations.

Contribution

It provides a detailed analysis of the NMSSM's ability to evade fine-tuning and explains the LEP Higgs excess via dominant $h o aa$ decays with specific mass and decay properties.

Findings

NMSSM allows a light Higgs near 100 GeV with minimal fine-tuning.

The model explains the LEP excess through $h o aa$ decays with $a o au^+ au^-$ or jets.

Scenarios with a singlet-like $a$ decaying to photons produce distinctive $h o aa o 4\gamma$ signals.

Abstract

We present an extended study of how the Next to Minimal Supersymmetric Model easily avoids fine-tuning in electroweak symmetry breaking for a SM-like light Higgs with mass in the vicinity of $100\gev$, as beautifully consistent with precision electroweak data, while escaping LEP constraints due to the dominance of $h\to aa$ decays with $m_a<2m_b$ so that $a\to \tauptaum$ or jets. The residual $\sim 10%$ branching ratio for $h\to b\anti b$ explains perfectly the well-known LEP excess at $\mh\sim 100\gev$. Details of model parameter correlations and requirements are discussed as a function $\tan(\beta)$. Comparisons of fine-tuning in the NMSSM to that in the MSSM are presented. We also discuss fine-tuning associated with scenarios in which the $a$ is essentially pure singlet, has mass $m_a>30\gev$, and decays primarily to $\gam\gam$ leading to an $h\to aa\to 4\gam$ Higgs signal.