arXiv subjects

Yuichiro Nakai

Publications and source records attributed to Yuichiro Nakai.

78 records · Page 5Linked to original sources

arXiv2011

(Extra)Ordinary Gauge/Anomaly Mediation

We study anomaly mediation models with gauge mediation effects from messengers which have a general renormalizable mass matrix with a supersymmetry-breaking spurion. Our models lead to a rich structure of supersymmetry breaking terms in the visible sector. We derive sum rules among the soft scalar masses for each generation. Our sum rules for the first and second generations are the same as those in general gauge mediation, but the sum rule for the third generation is different because of the top Yukawa coupling. We find the parameter space where the tachyonic slepton problem is solved. We also explore the case in which gauge mediation causes the anomalously small gaugino masses. Since anomaly mediation effects on the gaugino masses exist, we can obtain viable mass spectrum of the visible sector fields.

hep-ph↗

arXiv2011

Higgs Portal to Visible Supersymmetry Breaking

We propose a supersymmetric extension of the standard model whose Higgs sector induces a spontaneous supersymmetry breaking by itself. Unlike the minimal extension, the current Higgs mass bound can be evaded even at the tree-level without the help of the soft breaking terms due to the usual hidden sector, as is reminiscent of the next to minimal case. We also have a possibly light pseudo-goldstino in our visible sector in addition to extra Higgs particles, both of which stem from supersymmetry breaking dynamics. In such a setup of visible supersymmetry breaking, we may see a part of supersymmetry breaking dynamics rather directly in future experiments.

hep-ph↗

arXiv2011

Comments on Gaugino Mass and Landscape of Vacua

In direct gauge mediation, gaugino masses often vanish at the leading order of supersymmetry breaking. Recently, this phenomenon is understood in connection with the global structure of vacua in O'Raifeartaigh-type models. In this note, we further explore a connection between gaugino masses and the landscape of vacua in more general situations, focusing on a few examples which demonstrate our idea. In particular, we present a calculable model with non-vanishing leading order gaugino masses on the lowest energy vacuum.

hep-th↗

arXiv2010

Revisiting superparticle spectra in superconformal flavor models

We study superparticle spectra in the superconformal flavor scenario with non-universal gaugino masses. The non-universality of gaugino masses can lead to the wino-like or higgsino-like neutralino LSP. Furthermore, it is shown that the parameter space for the higgsino-like LSP includes the region where the fine-tuning problem can be improved. The degeneracy of soft scalar masses squared does not drastically change by taking ratios of gaugino masses of order one. The degeneracy of scalar masses for squarks and left-handed sleptons would be good to avoid the FCNC problem but that of right-handed slepton masses is weak. However, the overall size of right-handed slepton masses become larger when the bino becomes heavier. It is also pointed out that such region can be realized, and thus, that would be favorable to avoid the FCNC problem for soft scalar masses as well as A-terms.

hep-ph↗

arXiv2010

E6,7,8 Magnetized Extra Dimensional Models

We study 10D super Yang-Mills theory with the gauge groups $E_6$, $E_7$ and $E_8$. We consider the torus/orbifold compacfitication with magnetic fluxes and Wilson lines. They lead to 4D interesting models with three families of quarks and leptons, whose profiles in extra dimensions are quasi-localized because of magnetic fluxes.

hep-ph↗

arXiv2009

Fine Tuning in General Gauge Mediation

We study the fine-tuning problem in the context of general gauge mediation. Numerical analyses toward for relaxing fine-tuning are presented. We analyse the problem in typical three cases of the messenger scale, that is, GUT ($2\times10^{16}$ GeV), intermediate ($10^{10}$ GeV), and relatively low energy ($10^6$ GeV) scales. In each messenger scale, the parameter space reducing the degree of tuning as around 10% is found. Certain ratios among gluino mass, wino mass and soft scalar masses are favorable. It is shown that the favorable region becomes narrow as the messenger scale becomes lower, and tachyonic initial conditions of stop masses at the messenger scale are favored to relax the fine-tuning problem for the relatively low energy messenger scale. Our spectra would also be important from the viewpoint of the $μ-B$ problem.

hep-ph↗