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Register a new userR-Parity Violation and Supersymmetric Higgs Masses
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We consider the supersymmetric extension of the Standard Model with neutrino Yukawa interactions and R-parity violation. We found that R-parity breaking term lambda u H_u H_d leads to an additional F-type contribution to the Higgs scalar potential, and thus to the masses of supersymmetric Higgs bosons. The most interesting consequence is the modification of the tree-level expression for the lightest neutral supersymmetric Higgs boson mass. It appears that due to this contribution the bound on the lightest Higgs mass may be shifted upwards, thus slightly opening the part of the model parameter space excluded by non-observation of the light Higgs boson at LEP in the framework of the Minimal Supersymmetric Standard Model.
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We study the possibility of spontaneous CP violation in the next-to-minimal supersymmetric standard model (NMSSM). It is shown that the spontaneous CP violation is induced by the radiative effects of top, stop, bottom and sbottom superfields. The available regions of parameters, which are obtained by imposing the constraints from experiments, are rather narrow. We also obtain strong constraints for light Higgs masses such as m_H le 36 GeV numerically. Sum of masses of two light neutral Higgs should set around 93 GeV and charged Higgs boson has a rather higher mass larger than 700 GeV.
We present the complete 2-loop renormalisation group equations of the superpotential parameters for the supersymmetric standard model including the full set of R-parity violating couplings. We use these equations to do a study of (a) gauge coupling unification, (b) bottom-tau unification, (c) the fixed-point structure of the top quark Yukawa coupling, and (d) two-loop bounds from perturbative unification. For large values of the R-parity violating coupling, the value of alpha_S(M_Z) predicted from unification can be reduced by 5% with respect to the R-parity conserving case, bringing it to within 2sigma of the observed value. Bottom-tau Yukawa unification becomes potentially valid for any value of tanbetasim 2-50. The prediction of the top Yukawa coupling from the low tanbeta, infra-red quasi fixed point can be lowered by up to 10%, raising tanbeta up to a maximum of 5 and relaxing experimental constraints upon the quasi-fixed point scenario. For heavy scalar fermion masses of order 1 Tev the limits on the higher family Delta L ot=0 operators from perturbative unification are competitive with the indirect laboratory bounds. We calculate the dependence of these bounds upon tan beta.
We consider new s-channel scalar exchanges in e+e- -> ZZ,W+W- in supersymmetry with a small lepton number violation. We show that a small bilinear R-parity violating term which leads to sneutrino--Higgs mixing can give rise to a significant scalar resonance enhancement in e+e- -> ZZ,W+W-. We use the LEP2 measurements of the WW and ZZ cross-sections to place useful constraints on this scenario. We also find, under conservative assumptions on the relevant parameter space involved, that such an exchange of the sneutrino-like admixture in e+e- -> ZZ,W+W- may be accessible to a 500 GeV e+e- collider.
We study radiative gravitino decay within the framework of R-violating supersymmetry. For trilinear R-violating couplings that involve the third generation of fermions, or for light gravitinos, we find that the radiative loop-decay $tilde{G} to gamma u$ dominates over the tree-level ones for a wide set of parameters. We calculate the gravitino decay width and study its implications for cosmology and collider physics. Slow-decaying gravitinos are good dark matter candidates, for a range of parameters that would also predict observable R-violating signatures in colliders. In general the branching ratios are very dependent on the relative hierarchies of R-violating operators, and may provide relevant information on the flavour structure of the underlying fundamental theory.
Supersymmetry without R-parity predicts tree level quark flavor violation. We present a potential signal of single bottom production at electron-positron colliders with energies in the range 6 to 20 GeV. Taking into account rare decay limits it should be detectable with the current BaBar and Belle data samples.
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