2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/218040Higgs singlet superfields, usually present in extensions of the Minimal Supersymmetric Standard Model (MSSM) which address the $μ$-problem, such as the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and the Minimal Nonminimal Supersymmetric Standard Model (mnSSM), can have significant contributions to $B$-meson flavour-changing neutral current observables for large values of $\tanβ\gsim 50$. Illustrative results are presented including effects on the $B_s$ and on the rare decay $B_s\toμ^+μ^-$. In particular, we find that in the NMSSM, the branching ratio for $B_s\toμ^+μ^-$ can be enhanced or even suppressed with respect to the Standard Model prediction by more than one order of magnitude.3 pages, 4 figures, submitted to SUSY08 proceedingsHigh Energy Physics - Phenomenologytext