Constraining the light Higgs bosons in the GNMSSM with recent Higgs data

Abstract

The search for light scalar and pseudoscalar particles provides a promising avenue for probing physics beyond the Standard Model (SM). In this study, we investigated the exotic decay channels of the 125 GeV SM-like Higgs boson into pairs of light CP-odd ($a_s$) or CP-even ($h_s$) Higgs bosons within the framework of the General Next-to-Minimal Supersymmetric Standard Model (GNMSSM). A comprehensive parameter space scan is performed using the MultiNest algorithm, incorporating constraints from $ \textsf{HiggsSignals-2.6.2} $, $ \textsf{HiggsBounds-5.10.2} $, and ATLAS experimental searches, under two distinct scenarios where either the lightest ($h_1$) or next-to-lightest ($h_2$) CP-even state is the observed Higgs boson ($h$). Our results demonstrate that $ \textsf{HiggsBounds} $ imposes the most stringent exclusion limits due to its sensitivity to direct searches for non-SM Higgs bosons. In the $h_2$ scenario, $ \textsf{HiggsSignals} $ can additionally exclude regions with suppressed exotic branching ratios (e.g., $ Br(h \to a_sa_s \to ττbb) \leq 2.5\%$), due to its sensitivity to indirect deviations caused by the kinematically enhanced decay \( h \to h_sh_s \). Under combined constraints from \( \textsf{HiggsTools} \), $h$ must retain at least 93\% SM-like component (\( V_h^\text{SM} \geq 0.93 \)) with no more than 32\% singlet admixture (\( V_h^\text{S} \leq 0.32 \)); in the $ h_2 $ case, the lightest scalar $ h_s $ exhibits high singlet purity ($ V_{h_s}^\text{S} \geq 0.94 $). Furthermore, dark matter (DM) phenomenology indicates that singlino- or higgsino-dominated DM is viable in the $ h_1 $ scenario, with dominant annihilation channels including $ \tildeχ_1^0\tildeχ_1^0 \to h_sa_s $ for singlino-like DM and chargino co-annihilation for higgsino-like DM, whereas the $ h_2 $ scenario favors higgsino-dominated DM.