Exploring the NMSSM Parameter Space for the Asymmetric Higgs Decay 𝑿 → 𝑺(𝒃𝒃̅)𝑯(𝜸𝜸)

Sammanfattning

In an effort to solve the shortcomings of the Standard Model, supersymmetric extensions such as the Next–to–Minimal Supersymmetric Standard Model (NMSSM) have been proposed. This thesis investigates the NMSSM parameter space in relation to the asymmetric Higgs decay channel X → S(b¯b)H(γγ), motivated by recent exclusion contours in the m_X–m_S plane published by the CMS Collaboration. A subset of the NMSSM parameter space, specifically six parameters from the tree–level Higgs sector, is scanned using the NMSSMTools code, yielding over 140 000 viable NMSSM models under current experimental and theoretical constraints.The resulting models span many orders of magnitude in cross sections times branching ratios. Systematic variations of individual parameters reveal strong correlations, including a notable dependence of mS and the cross section σ(gg → X → S(b¯b)H(γγ)) on µ_eff, and significant variation in BR(S → b¯b) induced by changes in tan β,µ_eff,κ and A_λ. Cross sections from the viable models are compared to 95% confidence level (CL) upper limits published by ATLAS and CMS. While some NMSSM models exceed these limits, the vast majority fall well below them.These findings highlight the large variability of NMSSM predictions and show that only a small fraction of the allowed parameter space is currently excluded. The results suggest that exclusion contours based solely on maximal cross section values might give a misleading picture of how much of the parameter space current data can actually rule out, so a more nuanced interpretation is needed.