- The paper demonstrates that introducing a gauge singlet superfield generates an effective μ-term, thereby resolving the μ-problem of the MSSM.
- It reveals how the NMSSM expands the Higgs sector with additional CP-even and CP-odd states, potentially accommodating a heavier SM-like Higgs while meeting experimental constraints.
- The study investigates dark matter implications by analyzing a singlino-like neutralino LSP that offers unique relic density and detection prospects.
The Next-to-Minimal Supersymmetric Standard Model
The paper under review provides a comprehensive exploration of the theoretical and phenomenological aspects of the Next-to-Minimal Supersymmetric Standard Model (NMSSM), expanding upon the conventional Minimal Supersymmetric Standard Model (MSSM) by incorporating an additional gauge singlet superfield. This addition, sometimes referred to as the (M+1)SSM, is aimed at addressing the so-called "μ-problem" of the MSSM, where finding a natural value for the Higgs mass parameter μ at the electroweak scale poses significant challenges.
Key Aspects of the NMSSM
- Theoretical Motivation: Supersymmetric extensions like the NMSSM are motivated by the hierarchy problem, the unification of gauge couplings, and the possibility of accounting for dark matter through a stable, neutral particle. A critical aspect is that the NMSSM potentially solves the μ-problem by introducing an effective μ-term through the vev of a singlet scalar field.
- Higgs Sector: The NMSSM expands the Higgs sector to include new CP-even and CP-odd states due to the presence of the singlet. This leads to modified mass spectra and mixing patterns compared to the MSSM, potentially allowing for a heavier SM-like Higgs boson while still being compliant with LEP constraints. However, the NMSSM also introduces complex scenarios for Higgs-to-Higgs decays, which have significant implications for collider searches.
- Dark Matter and Cosmology: The NMSSM modifies neutralino and Higgs spectra, impacting the relic density of the lightest supersymmetric particle (LSP), a dark matter candidate. An important aspect is how the NMSSM accommodates a singlino-like neutralino LSP, which has different properties from those in the MSSM, affecting both direct and indirect detection strategies.
- Phenomenological Implications: The NMSSM opens a plethora of phenomenological possibilities at colliders. The presence of light singlet-like Higgs or pseudoscalar states can significantly alter the expected signals, especially in Higgs decays. This necessitates a re-evaluation of search strategies at the LHC and future colliders.
- Variants and Extensions: The paper also discusses variants of the NMSSM, including models with added symmetries or additional fields that can further modify the phenomenology. These extensions address issues like CP violation, neutrino masses, and more exotic scenarios like gauge-mediated supersymmetry breaking.
Numerical Results and Constraints
The authors highlight various numerical studies that explore the parameter space of the NMSSM. For instance, the upper bounds on the lightest CP-even Higgs mass in different regions of parameter space are derived, showing potential compatibility with current experimental limits. Additionally, they explore scenarios with light CP-odd scalars, which bear significant relevance to solving puzzles in B-meson decays and electroweak baryogenesis.
Future Outlook
The discussions in the paper speculate on future avenues in both theoretical explorations and experimental searches. As the LHC and next-generation colliders potentially continue to test and refine supersymmetric models, the implications of a singlet extension like the NMSSM might provide critical insights into new physics beyond the Standard Model.
In conclusion, the NMSSM offers a rich structure that extends the MSSM, addressing theoretical shortcomings while opening new horizons in both particle physics and cosmology. The insights gained from these explorations are expected to shape the ongoing discourse in the field of supersymmetric theories.