Top quark mass in supersymmetric SO(10) unification

Abstract

The successful prediction of the weak mixing angle suggests that the effective theory beneath the grand unification scale is the minimal supersymmetric standard model (MSSM) with just two Higgs doublets. If we further assume that the unified gauge group contains S0(10), that the two light Higgs doublets lie mostly in a single irreducible SO(10) representation, and that the t , b, and T masses originate in renormalizable Yukawa interactions of the form 1630163, then also the top quark mass can be predicted in terms of the MSSM parameters. To compute mt we present a precise analytic approximation to the solution of the two-loop renormalization group equations, and study supersymmetric and GUT threshold corrections and the input value of the b quark mass. The large ratio of top to bottom quark masses derives from a large ratio, tanp, Higgs vacuum expectation values. We point out that when tanp is large, so we certain corrections to the b quark mass prediction, unless a particular hierarchy exists in the parameters of the model. With such a hierarchy, which may result from approximate symmetries, the top mass prediction depends only weakly on the spectrum. Our results may be applied to any supersymmetric SO (10) model as long as At -X b N AT at the GUT scale and there are no intermediate mass scales in the desert. PACS number(s): 12.10.Dm, 12.15.Ff, 12.60.Jv, 14.65.Ha

Enhanced di-photon Higgs signal in the Next-to-Minimal Supersymmetric Standard Model

“…Squark/gluino loops can also contribute (notably for large tan β) to the coupling of H 1 to b quarks via its S 1,u -component [20][21][22]; in the present case the effective H 1 bb coupling increases by just about 10% due to this phenomenon. Hence it is not astonishing that the partial decay width Γ(H 1 → bb) is strongly reduced with respect to a SM-like Higgs boson; in fact the dominant contribution (about 60%) to Γ(H 1 → bb) comes from the dominantly top-quark loop induced H 1 gg * coupling (where g denotes a gluon) and a subsequent g * → bb decay.…”

The soft supersymmetry-breaking Lagrangian: theory and applications

“…Second, if the parameters of the Higgs potential are comparable in size, it is natural for the Higgs fields to have VEVs of similar magnitudes. One argument in the opposite direction is that the attractive idea that the t, b, and τ Yukawa couplings unify at a high scale requires large tan β [150,151,152,153,154,155,156,52,157,158]. Precisely how large is subtle, since one must include running effects on masses and higher order effects.…”

“…If any of these effects are seen they will greatly help determine the numerical value of tan β. First, there are large (nondecoupling) radiative corrections to the down-type quark masses (in particular the b quark mass) and couplings which then affect a number of observables [156,253,759]. The radiative corrections are large because the tan β enhancement can compensate the suppression from loop factors.…”

“…However, since supersymmetry is softly broken, one should expect that this property does not hold at higher orders in perturbation theory. Indeed, there are new effective flavor-changing couplings which arise from large loop corrections to the couplings of Higgs bosons to down-type quarks and leptons [156,155].…”

Analysis of the TeV-scale mirage mediation with heavy superparticles

“…The light extra Higgs bosons change the couplings between the 125-GeV Higgs boson and SM particles; especially, couplings with bottom quark and tau lepton can be largely deviated from the SM prediction [52][53][54][55][56]. There are recent studies about the precision measurements of the Higgs couplings [57][58][59].…”