de Sitter Thin Brane Model

We discuss the large mass hierarchy problem in a braneworld model which represents our acceleratively expanding universe. The Randall-Sundrum (RS) model with warped one extra dimension added to flat 4-dimensional space-time cannot describe our expanding universe. Here, we study instead the de Sitter thin brane model. This is described by the same action as that for the RS model, but the 4-dimensional space-time on the branes is $\rm dS_4$. We study the model for both the cases of positive 5-dimensional cosmological constant $\Lambda_5$ and negative one. In the positive $\Lambda_5$ case, the 4-dimensional large hierarchy necessitates a 5-dimensional large hierarchy, and we cannot get a natural explanation. On the other hand, in the negative $\Lambda_5$ case, the large hierarchy is naturally realized in the 5-dimensional theory in the same manner as in the RS model. Moreover, another large hierarchy between the Hubble parameter and the Planck scale is realized by the ${\mathcal O}(10^2)$ hierarchy of the 5-dimensional quantities. Finally, we find that the lightest mass of the massive Kaluza-Klein modes and the intervals of the mass spectrum are of order $10^2\,\rm GeV$, which are the same as in the RS case and do not depend on the value of the Hubble parameter.Comment: 24 pages, 6 figures. v5: published versio

A cell line derived from BBN (N-butyl-N-[4-hydroxybutyl]-nitrosamine)-induced rat bladder cancer: establishment and scanning electron microscopic cell surface characteristics

This research was performed to establish a cell line from experimental bladder tumor and to discuss the biological characteristics of the cell line so established. Tissue cultures of epithelial cells were derived from a rat bladder cancer induced by BBN. The cells showed loss of contact inhibition and the phenomenon of piling up after several subcultures. Colonial cloning was used. The population doubling time of the wild strain and the colonial clones was about 30 h. The chromosomal mode ranged from triploid to tetraploid to tetraploid. Plating efficiency was well below 20%. Intraperitoneal backtransplantation into newborn Wister rats resulted in tumors in all cases. These tumors, in some parts, resembled primary transitional cell carcinoma. The major tumor cell groups, however, showed marked keratinization and the picture of squamous cell carcinoma. The nucleus/cytoplasm ratio and the numbers of nuclei, free ribosomes and intracytoplasmic microfibrils were increased. Dense microvillus arrangements characterized the electron microscopic picture. During the mitotic phase, the cells became large and globular whereas the microvilli were relatively short and were gathered profusely over the whole surface. Cells in the gap 1-synthetic phase developed lamellipodia and pseudpodia-like cytoplasmic processes and were polygonal in shape. Microvilli were present in the central part containing the nucleus, but their numbers were somewhat decreased and their height increased (scanning electron microscopy).</p

Intrinsic flavor violation for massive neutrinos

It is shown that intrinsic neutrino flavor violation invariably occurs when neutrinos are created within the SM augmented by the known massive neutrinos, with mixing and nondegenerate masses. The effects are very small but much greater than the naive estimate $\Delta m^2/E_\nu^2$ or the branching ratio of indirect flavor violating processes such as $\mu\to e\gamma$ within the SM. We specifically calculate the probability (branching ratio) of pion decay processes with flavor violation, such as $\pi\to \mu\bar{\nu}_e$, showing nonzero results.Comment: v3: published versio

Compatible abelian symmetries in N-Higgs-Doublet Models

We analyze the compatibility between abelian symmetries acting in two different sectors of a theory using the Smith Normal Form method. We focus on N-Higgs-doublet models (NHDMs) and on the compatibility between symmetries in the Higgs potential and in the Yukawa interactions, which were separately analyzed previous works. It is shown that two equal (isomorphic) symmetry groups that act in two separate sectors are not necessarily compatible in the whole theory and an upper bound is found for the size of the group that can be implemented in the entire NHDM. We also develop useful techniques to analyze compatibility and extend a symmetry from one sector to another. Consequences to the supersymmetric case are briefly discussed.Comment: v2: 40pp; some modifications in text, brief discussion on the supersymmetric case added; to appear in JHE

Imaging Gaseous Detector based on Micro Processing Technology

The development of gaseous detectors has been exciting again since the appearance of a MicroStrip Gas Chamber(MSGC) in 1988, which is made using a micro-electronics technology. These days lots of variations of the advanced gaseous detectors are being intensively studied in the world. We have developed the two-dimensional MSGC having a 10 cm square detection area and the ultra fast readout system for a real time X-ray imaging. The MSGC was made using Multi-Chip Module (MCM) technology, and has a very thin substrate of 17 $\mu$m, lots of thin anodes and back strips both with 200 $\mu$m pitches. This enables us to get fast digital X-ray images with recording both the timing and an energy of each X-ray photon. In addition, an intermediate gas multiplier has been realized using a capillary plate having a conductive surface of a capillary. The MSGC combined with the conductive capillary plate can be steadily operated with a high gain under intense irradiation. Here we also report new approaches of X-ray crystal structure analyses using timing information obtained by the MSGC.Comment: 14 papges, 10 figures, to appear in the proceedings of Solid State Detectors for 21st Century (Nucl. Instru. and Meth. A