arXiv subjects
Publications and source records attributed to Yoshiharu Kawamura.
We give a generic method to select a realistic $μ$-term generation mechanism based on the radiative electroweak symmetry breaking scenario and study which type is hopeful within the framework of string theory. We discuss effects of the moduli F-term condensation and D-term contribution to soft scalar masses.
It is shown that a certain sum rule for soft supersymmetry-breaking scalar masses, which has been recently found in a certain class of superstring models, is universal for gauge-Yukawa unified models. To explain this coincidence, we argue that the low-energy remnant of the target-space duality invariance in the effective supergravity of compactified superstrings can be identified with the (broken) scale invariance in gauge-Yukawa unified models, and that gauge-Yukawa unification which is indispensable for the sum rule to be satisfied follows from the matching of anomalies.
We study flat directions and soft scalar masses using a $Z_3$ orbifold model with $SU(3) \times SU(2) \times U(1)$ gauge group and extra gauge symmetries including an anomalous $U(1)$ symmetry. Soft scalar masses contain $D$-term contributions and particle mixing effects after symmetry breaking and they are parametrized by a few number of parameters. Some specific relations among scalar masses are obtained.
We derive formula of soft supersymmetry breaking scalar masses from 4-dimensional string models within a more generic framework. We consider effects of extra gauge symmetry breakings including an anomalous $U(1)$ breaking through flat directions, that is, $D$-term and $F$-term contributions, particle mixing effects and heavy-light mass mixing effects. Some phenomenological implications are discussed based on our mass formula.
We study generic features related to matter contents and flat directions in $Z_{2n}$ orbifold models. It is shown that $Z_{2n}$ orbifold models have massless conjugate pairs, $R$ and $\overline R$, in certain twisted sectors as well as one of untwisted subsectors. Using these twisted sectors, $Z_{2n}$ orbifold models are classified into two types. Conjugate pairs, $R$ and $\overline R$, lead to $D$-flatness as $\langle R \rangle = \langle \overline R \rangle \neq 0$. We investigate generic superpotentials derived from orbifold models so as to show that this direction is indeed a flat direction.
We obtain the low-energy effective theory from string models with anomalous $U(1)$ symmetry. The feature of soft supersymmetry breaking scalar masses and some phenomenological implications are discussed. We show that it is, in general, difficult to keep the degeneracy and the positivity of squared soft scalar masses at the Planck scale.
Starting from non-minimal supergravity theory with unified gauge symmetry, we obtain the low-energy effective theory by taking the flat limit and integrating out the superheavy fields in a model-independent manner. The scalar potential has extra non-universal contributions to soft supersymmetry breaking terms which can give an impact on phenomenological study.
From general supergravity theory with unified gauge symmetry, we obtain the low-energy effective Lagrangian by taking the flat limit and integrating out the superheavy fields in model-independent manner. The scalar potential possesses some excellent features. Some light fields classified by using supersymmetric fermion mass, in general, would get intermediate masses at the tree level after the supersymmetry is broken. We show that the stability of weak scale can be guaranteed under some conditions. There exist extra non-universal contributions to soft supersymmetry breaking terms which can give an impact on phenomenological study.
In supersymmetric grand unified theories, the gauge hierarchy achieved by a fine-tuning in the superpotential can be violated in the presence of soft breaking terms. We examine this problem in Einstein supergravity with hidden-sector supersymmetry breaking. We show that the hierarchy is preserved if couplings of the hidden sector to visible-sector fields in the superpotential satisfy a certain requirement.
Supersymmetric grand unified theories with non-universal soft supersymmetry breaking terms are studied. By integrating out the superheavy fields at an unification scale, we compute their low-energy effective Lagrangian. We find new contributions to the scalar potential specific to the non-universal supersymmetry breaking. $D$-term contribution to the scalar masses is one example. The gauge hierarchy achieved by a fine-tuning in the superpotential would be violated in general due to the non-universal SUSY breaking terms. We show, however, it is preserved for a certain class of the soft terms derived from a {\em hidden} ansatz. We also discuss some phenomenological implications of the non-universal supersymmetry breaking, including predictions of the radiative electroweak symmetry breaking scenario and of no-scale type models.
We study the mass spectrum of superparticles within supersymmetric grand unified models. For gaugino masses, it is pointed out that the GUT-relation in the $SU(5)$ model is applicable to a more general case where a grand-unified gauge group breaks down to the standard model gauge group by several steps. We also show that the mass spectrum of squarks and sleptons carries the information on the breaking pattern of the gauge symmetry. It is demonstrated in some $SO(10)$ models how the scalar mass spectrum distinguishes various $SO(10)$ breaking patterns from each other.