Due to the additional singlet S, the NMSSM alters in general the phenomenology of both the Higgs sector and the neutralino sector compared with the MSSM.
Higgs phenomenology In the Standard Model we have one physical Higgs boson. In the MSSM we encounter five physical Higgs bosons. Due to the additional singlet \hat{S} in the NMSSM we have two more Higgs bosons; that is, in total seven physical Higgs bosons. Its Higgs sector is therefore much richer than that of the MSSM. In particular, the Higgs potential is in general no longer invariant under CP transformations; see
CP violation. Typically, the Higgs bosons in the NMSSM are denoted in an order with increasing masses; that is, by H_1, H_2, ..., H_7, with H_1 the lightest Higgs boson. In the special case of a CP-conserving Higgs potential we have three CP even Higgs bosons, H_1, H_2, H_3, two CP odd ones, A_1, A_2, and a pair of charged Higgs bosons, H^+, H^-. In the MSSM, the lightest Higgs boson is always Standard Model-like, and therefore its production and decays are roughly known. In the NMSSM, the lightest Higgs can be very light (even of the order of 1 GeV), and thus may have escaped detection so far. In addition, in the CP-conserving case, the lightest CP even Higgs boson turns out to have an enhanced lower bound compared with the MSSM. This is one of the reasons why the NMSSM has been the focus of much attention in recent years.
Neutralino phenomenology The spin-1/2 singlino \tilde{S} gives a fifth neutralino, compared with the four neutralinos of the MSSM. The singlino does not couple with any gauge bosons, gauginos (the superpartners of the gauge bosons), leptons, sleptons (the superpartners of the leptons), quarks or squarks (the superpartners of the quarks). Suppose that a supersymmetric partner particle is produced at a collider, for instance at the
LHC, the singlino is omitted in cascade decays and therefore escapes detection. However, if the singlino is the
lightest supersymmetric particle (LSP), all supersymmetric partner particles eventually decay into the singlino. Due to
R parity conservation this LSP is stable. In this way the singlino could be detected via missing transverse energy in a detector. == References ==