Singlino dominated LSP as CDM candidate in supersymmetric models with an extra U(1)

We consider a singlino dominated neutralino in supersymmetric models with an extra U(1). In case both the $\mu$ term and also the $Z^\prime$ mass are generated by the vacuum expectation value of the scalar component of the same singlet chiral superfield, generically the lightest neutralino is not expected to be dominated by the singlino. However, if the gaugino corresponding to the extra U(1) is sufficiently heavy, the lightest neutralino can be dominated by the singlino and still satisfy the constraints resulting from the $Z^\prime$ phenomenology. We assume a supersymmetry breaking scenario in which the extra U(1) gaugino can be much heavier than other gauginos. In that framework we show that the singlino dominated lightest neutralino may be a good candidate for dark matter in a parameter space where various phenomenological constraints are satisfied.Comment: 25 pages, 6 figures, title is changed, introduction is extended, sec.2 is moved to appendix, some references are added, published versio

D-term inflation and neutrino mass

We study a $D$-term inflation scenario in a model extended from the minimal supersymmetric standard model (MSSM) by two additional abelian factor groups focussing on its particle physics aspects. Condensates of the fields related to the inflation can naturally give a possible solution to both the $\mu$-problem in the MSSM and the neutrino mass through their nonrenormalizable couplings to the MSSM fields. Mixings between neutrinos and neutralinos are also induced by some of these condensates. Small neutrino masses are generated by a weak scale seesaw mechanism as a result of these mixings. Moreover, the decay of the condensates may be able to cause the leptogenesis. Usually known discrepancy between both values of a Fayet-Iliopoulos $D$-term which are predicted by the COBE normalization and also by an anomalous U(1) in the weakly-coupled superstring might be reconciled.Comment: 21 pages, LaTeX, small modifications, one reference adde

Radiative symmetry breaking and Higgs mass bound in the NMSSM

We study the upper mass bound of the lightest neutral Higgs scalar in the NMSSM using the RGE analysis. We require the successful occurence of the electroweak radiative symmetry breaking to restrict the parameter space. As a result the upper mass bound $m_{h^0}$ is largely restricted compared with the one estimated without imposing this condition. We point out some features of $m_{h^0}$ related to the initial value of $h_t$ and discuss why the models with more extra matters ${\bf 5}+\bar{\bf 5}$ of SU(5) could bring the larger maximum value of $m_{h^0}$.Comment: 8 pages, latex, 4 eps-figure

SUSY breaking based on Abelian gaugino kinetic term mixings

We present a SUSY breaking scenario based on Abelian gaugino kinetic term mixings between hidden and observable sectors. If an extra U(1) gaugino in the observable sector obtains a large mass through this mixing effect based on SUSY breaking in the hidden sector, soft SUSY breaking parameters in the MSSM may be affected by radiative effects due to this gaugino mass. New phenomenological aspects are discussed in such a SUSY breaking scenario.Comment: latex, 12pages, 2figures, published versio

Reconciliation of CDM abundance and μ→eγ\mu\to e\gamma in a radiative seesaw model

We reexamine relic abundance of a singlet fermion as a CDM candidate, which contributes to the neutrino mass generation through radiative seesaw mechanism. We search solutions for Yukawa couplings and the mass spectrum of relevant fields to explain neutrino oscillation data. For such solutions, we show that an abundance of a lightest singlet fermion can be consistent with WMAP data without conflicting with both bounds of $\mu\to e\gamma$ and $\tau\to \mu\gamma$. This reconciliation does not need any modification of the original radiative seesaw model other than by specifying flavor structure of Yukawa couplings and taking account of coannihilation effects.Comment: 16 pages, 2 figures, accepted version for publication

Gaugino CP phases and EDMs in the extended gauge mediation SUSY breaking

We study phenomenological aspects of the soft supersymmetry breaking parameters in a model with the extended gauge mediation supersymmetry breaking. In this model gaugino masses can be non-universal and as its result physical CP-phases remain in the gaugino sector even after the R-transformation. These phases contribute to the electric dipole moment (EDM) of an electron and a neutron. We show that their experimental bounds can be satisfied even for the situation such that there exist the order one CP-phases and the masses of superpartners are of the order of 100 GeV.Comment: LaTeX, 26 pages, 6 figure