arXiv subjects

Yutaka Sakamura

Publications and source records attributed to Yutaka Sakamura.

64 records · Page 4Linked to original sources

arXiv2003

Modified mode-expansion on a BPS wall related to the nonlinear realization

We propose a modified mode-expansion of the bulk fields in a BPS domain wall background to obtain the effective theory on the wall. The broken SUSY is nonlinearly realized on each mode defined by our mode-expansion. Our work clarifies a relation between two different approaches to derive the effective theory on a BPS wall, {\it i.e.} the nonlinear realization approach and the mode-expansion approach. We also discuss a further modification that respects the Lorentz and $U(1)_R$ symmetries broken by the wall.

hep-th↗

arXiv2001

SUSY Breaking by stable non-BPS configurations

A simple mechanism for SUSY breaking is proposed due to the coexistence of BPS domain walls. It requires no messenger fields nor complicated SUSY breaking sector on any of the walls. We assumed that our world is on a BPS domain wall and that the other BPS wall breaks the SUSY preserved by our wall. We obtain an ${\cal N}=1$ model in four dimensions which admits an exact solution of a stable non-BPS configuration of two walls. The stability is assured by a topological quantum number associated with the winding on the field space of the topology of $S^1$. We propose that the overlap of the wave functions of the Nambu-Goldstone fermion and those of physical fields provides a practical method to evaluate SUSY breaking mass splitting on our wall thanks to a low-energy theorem. This is based on our recent works hep-th/0009023 and hep-th/0107204.

hep-th↗

arXiv2001

Simple SUSY Breaking Mechanism by Coexisting Walls

A SUSY breaking mechanism with no messenger fields is proposed. We assume that our world is on a domain wall and SUSY is broken only by the coexistence of another wall with some distance from our wall. We find an ${\cal N}=1$ model in four dimensions which admits an exact solution of a stable non-BPS configuration of two walls and studied its properties explicitly. We work out how various soft SUSY breaking terms can arise in our framework. Phenomenological implications are briefly discussed. We also find that effective SUSY breaking scale becomes exponentially small as the distance between two walls grows.

hep-th↗

arXiv2001

SUSY Breaking by Stable non-BPS Walls

A new simple mechanism for SUSY breaking is proposed due to the coexistence of BPS domain walls. It is assumed that our world is on a BPS domain wall and that the other BPS wall breaks the SUSY preserved by our wall. This mechanism requires no messenger fields nor complicated SUSY breaking sector on any of the walls. We obtain an ${\cal N}=1$ model in four dimensions which has an exact solution of a stable non-BPS configuration of two walls. We propose that the overlap of the wave functions of the N-G fermion and those of physical fields provides a practical method to evaluate SUSY breaking mass splitting on our wall thanks to a low-energy theorem. This is based on our recent works hep-th/0009023 and hep-th/0107204.

hep-th↗

arXiv2001

Our wall as the origin of CP violation

A possibility that the origin of the CP violation in our world is a domain wall itself, on which we are living, is investigated in the context of the brane world scenario. We estimate the amount of the CP violation on our wall, and show that either of order one or suppressed CP phases can be realized. An interesting case where CP is violated due to the {\it coexistence} of the walls, which conserve CP individually, is also considered. We also propose a useful approximation for the estimation of the CP violation in the double-wall background.

hep-th↗

arXiv2000

SUSY Breaking by Overlap of Wave Functions in Coexisting Walls

SUSY breaking without messenger fields is proposed. We assume that our world is on a wall and SUSY is broken only by the coexistence of another wall with some distance from our wall. The Nambu-Goldstone fermion is localized on the distant wall. Its overlap with the wave functions of physical fields on our wall gives the mass splitting of physical fields on our wall thanks to a low-energy theorem. We propose that this overlap provides a practical method to evaluate mass splitting in models with SUSY breaking due to the coexisting walls.

hep-th↗

arXiv2000

Spontaneous CP violation model with flavor symmetry in large extra dimensions

We construct the minimal SUSY model that causes spontaneous CP violation with an abelian flavor symmetry in the context of the large extra dimensions and show that various phenomenological problems can be solved by introducing only scales below the low fundamental scale. We also realize the realistic size of the CP violation and the small masses of the neutrinos. The strong CP problem can be solved by the axion scenario and the axion can be made invisible by introducing an additional large extra dimension.

hep-ph↗

arXiv1999

Spontaneous CP Violation in Large Extra Dimensions

We show that in the context of large extra dimensions enough CP violation can be obtained from the spontaneous breaking in a simple non-SUSY model, which is usually considered not to cause the spontaneous CP violation. We estimate ε_{K} in our scenario to be of order 10^{-3} consistent with the experimental value. We also propose a modification to the see-saw mechanism and axion scenario to match with our model.

hep-ph↗

arXiv1999

Development of a Laser Wire Beam Profile Monitor (I)

A conceptual design work and a basic experimental study of a new beam profile monitor have been performed. The monitor will be used to measure emittance of an electron beam in the ATF damping ring at KEK, in which the transverse beam size of about 10 micron is expected. It utilizes a CW laser and an optical cavity, instead of a material wire, to minimize interference with an electron beam. A laser beam with a very thin waist is realized by employing the cavity of nearly concentric mirror configuration while the intensity is amplified by adjusting the cavity length to a Fabry-Perot resonance condition. We built a test cavity to establish a method to measure important parameters such as a laser beam waist and a power enhancement factor. Three independent methods were examined for the measurement of the beam waist. It was found that the cavity realized the beam waist of 20 micron with the power enhancement factor of 50.

hep-ex↗

arXiv1999

The Higgs mass bound in the SUSY multi-Higgs-doublet model

The upper bound on the mass of the lightest Higgs boson is provided in the supersymmetric standard model with multi-Higgs doublets, up to two-loop order. Relatively large corrections are expected from the experimentally unconstrained extra Yukawa couplings. We calculate it including the two-loop leading-log contributions as a function of the scale $Λ$, below which the theory remains perturbative. Even for $Λ=10^{4}$ GeV, we obtain the upper bound of 140 GeV, which is heavier than that of the MSSM by 10 GeV.

hep-ph↗