arXiv subjects
Publications and source records attributed to K. Hasegawa.
We obtain the condition to protect the baryon number in the $SU(2)_{L}$ triplet Higgs model. The obtained condition gives the upper limits for either of the two kinds of the coupling constants which are newly introduced in addition to ones in the standard model.
We discuss a possible scenario to solve the hierarchy problem, in which 4-dimensional bosonic fields with all possible integer spins, graviton, gauge boson and Higgs are unified in a framework of a gravity theory with extra dimensions. The Higgs is identified with the extra space component of the metric tensor. One-loop quantum effect on the Higgs mass-squared is explicitly calculated in a five dimensional gravity theory compactified on $S^1$. We obtain a finite calculable Higgs mass-squared without suffering from quadratic divergence, by virtue of general coordinate transformation invariance, which is argued to be guaranteed by the summation over all Kaluza-Klein modes running in the loop diagrams.
We find the condition that the primordial baryon asymmetry is not washed out in the $SU(2)_{L}$ triplet Higgs model by solving the Boltzmann equation. We further require that the model is compatible with the recent results of the neutrino oscillation experiments and WMAP, and the constraints on the $ρ$ parameter imposed by the LEP. We finally obtain the allowed region of the parameters in the model.
We discuss a possibility to solve the gauge hierarchy problem in the framework of Gravity-Gauge-Higgs Unification scenario. We have calculated 1-loop correction to the mass of the scalar field, which is originated from 55-component of the metric, in five dimensional gravity theory with the bulk scalar field compactified on S^1. It is shown that the quadratic divergences are canceled and the finite mass is generated by explicit diagrammatic calculations and the effective potential calculations.
We propose a two-zero-texture general Zee model, compatible with the large mixing angle Mikheyev-Smirnov-Wolfenstein solution. The washing out of the baryon number does not occur in this model for an adequate parameter range. We check the consistency of a model with the constraints coming from flavor changing neutral current processes, the recent cosmic microwave background observation, and the Z-burst scenario.
We require that the primordial baryon asymmetry is not washed out in the seesaw model compatible with the recent results of WMAP and the neutrino oscillation experiments including the first results of KamLAND. We find that only the case of the normal neutrino mass hierarchy with an approximate $L_{e}$-symmetry satisfies the requirement. We further derive, depending on the signs of neutrino mass eigenvalues, three types of neutrino mass matrixes, where the values of each element are rather precisely fixed.
The ohmic conductivity of the sol-gel derived Pb1+y(Zr0.3Ti0.7)O3 thin films (with the excess lead y=0.0 to 0.4) are investigated using low frequency small signal alternate current (AC) and direct current (DC) methods. Its temperature dependence shows two activation energies of 0.26 and 0.12 eV depending on temperature range and excess Pb levels. The former is associated with Pb3+ acceptor centers, while the latter could be due to a different defect level yet to be identified.
KEK-ATF is studying the low-emittance multi-bunch electron beam for the future linear collider. In ATF, thermionic gun is used to generate 20 bunches electron beam with the bunch spacing of 2.8 ns. Due to a distortion of the gun emission and the beam loading effect in the bunching system, the intensity for each bunch is not uniform by up to 40 % at the end of the injector. We have developed a system to correct the gun emission by precisely controlling the cathode voltage with a function generator. For the beam loading effect, we have introduced RF amplitude modulation on Sub Harmonic Buncher, SHB. By these technique, bunch intensity uniformity was improved and beam transmission for later bunches was recovered from 67% to 91%, but intensity for first five bunches is still lower than others.
The JAERI/KEK Joint Project for the high-intensity proton accelerator facility has been proposed with a superconducting (SC) linac option from 400 MeV to 600MeV. System design of the SC linac has been carried out based on the equipartitioning concept. The SC linac is planned to use as an injector to a 3GeV rapid cycling synchrotron (RCS) for spallation neutron source after it meets requirement to momentum spread less than +-0.1%. In the R&D work for SC cavities, vertical tests of single-cell and 5 cell cavities were performed. Experiments on multi-cell (5 cell) cavities of b=0.50 and b=0.89 at 2K were carried out with values of maximum electric surface peak fields of 23MV/m and 31MV/m, respectively. A model describing dynamic Lorentz detuning for SC cavities has been developed for pulse mode operation. Validity of the model was confirmed experimentally to simulate the performance.
We elaborate the trigonometric version of intertwining vectors and factorized L-operators. The starting point is the corresponding elliptic construction with Belavin's R-matrix. The naive trigonometric limit is singular and a careful analysis is needed. It is shown that the construction admits several different trigonometric degenerations. As a by-product, a quantum Lax operator for the trigonometric Ruijsenaars model intertwined by a non-dynamical R-matrix is obtained. The latter differs from the standard trigonometric R-matrix of $A_n$ type. A connection with the dynamical R-matrix approach is discussed.