S.-G. Kim

LHC signature of supersymmetric models with non-universal sfermion masses

We study the LHC signature of the minimal supersymmetric standard model with non-universal sfermion masses. In the model, soft masses of gauginos and the 3rd generation of 10 of SU(5) are around the weak scale, while other sfermion soft mass is universal and around a few TeV. Such sfermion mass spectrum is motivated not only from flavor, CP and naturalness constraints but also from E6 grand unified model with non-Abelian horizontal (flavor) symmetry. The characteristic signature of the model at the LHC is the dominance of the events with 4 b partons in the final state together with high rate of mildly boosted top quark arising from gluino decay. The prominent high pT jet also arises from squark decay. We show it is possible to find the characteristic signature in the early stage of the LHC. The discrimination of our scenario from some CMSSM model points with similar signature may be possible with large integrated luminosity. The result of sparticle mass measurement using exclusive channel with the help of hemisphere analysis, and inclusive measurement of gluino and squark masses using MT2 and MT2min in some representative model points are presented.

A Solution for little hierarchy problem and b ---> s gamma

We show that all the parameters which destabilize the weak scale can be taken around the weak scale in the MSSM without conflicting with the SM Higgs mass bound set by LEP experiment. The essential point is that if the lightest CP-even Higgs h in the MSSM has only a small coupling to Z boson, g_{ZZh}, LEP cannot generate the Higgs sufficiently. In the scenario, the SM Higgs mass bound constrains the mass of the heaviest CP-even Higgs H which has the SM like g_{ZZH} coupling. However, it is easier to make the heaviest Higgs heavy by the effect of off-diagonal elements of the mass matrix of the CP-even Higgs because the larger eigenvalue of 2 times 2 matrix becomes larger by introducing off-diagonal elements. Thus, the smaller stop masses can be consistent with the LEP constraints. Moreover, the two excesses observed at LEP Higgs search can naturally be explained as the signals of the MSSM Higgs h and H in this scenario. One of the most interesting results in the scenario is that all the Higgs in the MSSM have the weak scale masses. For example, the charged Higgs mass should be around 130 GeV. This looks inconsistent with the lower bound obtained by the b --> s gamma process as m_{H^\pm}>350GeV. However, we show that the amplitude induced by the charged Higgs can naturally be compensated by that of the chargino if we take the mass parameters by which the little hierarchy problem can be solved. The point is that the both amplitudes have the same order of magnitudes when all the fields in the both loops have the same order of masses.

CEDM constraints on modified sfermion universality and spontaneous CP violation

We discuss the supersymmetric CP problem that arises when the sfermion soft mass universality is modified. We place the 3rd generation SU(5) 10-plet sfermion masses in the weak scale in view of the naturalness. The other sfermion masses are assumed to be universal and to be of order a TeV scale to weaken the flavor changing neutral current processes and electric dipole moment (EDM) constraints. However, this modification generically induces very large up quark chromo-EDM (CEDM) via the weak-scale stop loop. To suppress this CEDM, we propose a certain type of flavor structure where the parameters of the up(s)quark sector are real, whereas those of the down-(s)quark and charged (s)lepton sectors are complex at the grand unified theory (GUT) scale. It is shown that, in this setup, up quark CEDM can be suppressed within the range where the current and future experiments have their sensitivity. We briefly illustrate the simple realization of these particular forms of the modified sfermion universality with real up-(s)quark sector by spontaneous CP violation in E6 SUSY GUT with SU(2) flavor symmetry. Subject Index: 113, 140, 142, 152, 158

Lepton flavor violation in a supersymmetric grand unified theory model with nonuniversal sfermion masses

We analyze lepton flavor violating {tau}{yields}{mu}{gamma} and {mu}{yields}e{gamma} processes in a supersymmetric grand unified theory model in which sfermions have a special mass spectrum. It is assumed that only third generation sfermions which are contained in 10(Q,U{sup c},E{sup c}) of SU(5) can have a different mass from the others. This mass spectrum is derived from the E{sub 6} grand unified theory model with horizontal symmetries. It is shown that branching ratios of {tau}{yields}{mu}{gamma} and {mu}{yields}e{gamma} depend strongly on a right-handed stau mass. The weak scale stability requires a light stau, so large decay rates can be expected in this scenario. When the stau mass is around 150 GeV and tan{beta}{approx}10, the branching ratios can be larger than Br({tau}{yields}{mu}{gamma}){approx_equal}10{sup -8} and Br({mu}{yields}e{gamma}){approx_equal}5x10{sup -12}, which are within reach of future experiments. In addition, this model has an interesting feature that the final state charged lepton tends to have right-handed chirality.

Neutralino dark matter in the minimal supersymmetric standard model with natural light Higgs sector

We study the neutralino relic density in the minimal supersymmetric standard model with natural light Higgs sector in which all Higgs masses, the supersymmetry (SUSY) breaking parameters, and the Higgsino mass parameter {mu} are of order the weak scale. To realize this situation we adopt nonuniversal Higgs masses at the grand unified scale. We show that in some parameter space in which the SUSY breaking parameters are comparatively small, not only the constraint from the observed relic density of dark matter but also the LEP Higgs bound and the constraint from the b{yields}s{gamma} process are satisfied. In most of the parameter space, the neutralino relic density becomes smaller than the observed relic density in contrast with the results in the constrained minimal SUSY standard model (CMSSM). The reason is that the neutralino coannihilation processes to Higgs bosons open even if the gaugino mass is small and the cross sections become large due to the small dimensionful parameters. Especially the small {mu} parameter and the light CP-odd Higgs, which are difficult to be realized in the CMSSM, are essential for the result.

Spontaneous supersymmetry breaking with anomalous U ( 1 ) symmetry in metastable vacua and moduli stabilization

We show that in (anomalous)

SUSY CP problem and spontaneous CP violation in SUSY GUT

U(1)

Spontaneous CP violation in E(6) SUSY GUT with SU(2) flavor and anomalous U(1) symmetries

gauge theories with the Fayet-Iliopoulos term and with generic interactions, there are metastable vacua in which supersymmetry (SUSY) is spontaneously broken even without

CP asymmetries of B to phi K_S and B to eta' K_S in SUSY GUT Model with Non-universal Sfermion Masses

U(1{)}_{R}

D-term assisted Anomaly Mediation in E6 motivated models

symmetry. In this vacua, various hierarchical structures such as Yukawa hierarchy can be explained by the smallness of the Fayet-Iliopoulos parameter. It is shown that, by adding just one positively charged field to phenomenologically viable models, spontaneous SUSY breaking is realized. Moreover, we propose a new scenario for the stabilization of the moduli in the SUSY breaking models. It is a new feature that the moduli can be stabilized without the superpotential being dependent on them.