arXiv subjects

M. Bando

Publications and source records attributed to M. Bando.

7 recordsLinked to original sources

arXiv2004

Pentaquark Baryons in String Theory -- Talk at Pentaquark 04

Pentaquark baryons $Θ^{+}$ and $Ξ^{--}$ are studied in the dual gravity theory of QCD in which simple mass formulae of pentaquarks are derived in the Maldacena prototype model for supersymmetric QCD and a more realistic model for ordinary QCD. In this approach it is possible to explain the extremely narrow decay widths of pentaquarks. With the aim of constructing more reliable mass formulae, a sketch is given on spin and the hyperfine interaction in the string picture.

hep-ph↗

arXiv2000

Mass Matrices in E6 Unification

We study a supersymmetric E6 grand unified model in which the SU(5) 5^* components are twisted in the third generation 27. Supplementing the adjoint Higgs field to a model analyzed previously, we calculate the mass matrices for the up and down quarks and charged leptons. Although the number of free parameters is less than that of observables, an overall fitting to the observed masses and mixing angles is shown to be possible. Most notably, we find two novel, parameter-independent relations between the lepton 2-3 mixing angle and the quark masses and CKM mixing angles that are in good agreement with the large lepton mixing recently observed.

hep-ph↗

arXiv1999

Brane fluctuations and suppression of Kaluza-Klein mode couplings

In higher dimensional models where the gauge and gravity fields live in the bulk and the matter fields only in a brane, we point out the importance of the brane (transverse) coordinate modes, which are the Nambu-Goldstone bosons appearing as a result of spontaneous breaking of the translation symmetry. The brane recoil effect suppresses the couplings of higher Kaluza-Klein modes to the matter, and gives a natural resolution to the divergence problem caused by the exchange of infinitely many Kaluza-Klein modes.

hep-ph↗

arXiv1998

Quark and Lepton Mass Matrix in an Asymptotically Non-Free Theory

We analyze fermion mass-matrix structure in an asymptotically non-free model with 4 + 1bar generations. The texture at the GUT scale is uniquely determined by supposing that the masses of heavy up-type quarks (charm as well as top) are realized as their infrared fixed point values. By assuming SO(10) GUT-like relations for Yukawa couplings in this model, this texture can explain all fermion masses and quark mixing with only one small parameter, which is almost equal to the Cabibbo angle.

hep-ph↗

arXiv1998

Neutrino Mass Texture with Large Mixing

We propose a simple texture for the right-handed Majorana mass matrix to give a large $ν_μ-ν_τ$ mixing angle and hierarchical left-handed neutrino mass pattern. Consistently with the Dirac mass texture of the quark sector realizing the CKM mixing, this naturally explains the recent experimental results on both the atmospheric neutrino anomaly observed by the Superkamiokande collaboration and the solar neutrino problem. In this texture the right-handed Majorana mass of the third generation is of the order of GUT scale, which is favorable for reproducing the observed bottom-tau mass ratio.

hep-ph↗

arXiv1996

Dynamical Gauge Boson and Strong-Weak Reciprocity

It is proposed that asymptotically nonfree gauge theories are consistently interpreted as theories of composite gauge bosons. It is argued that when hidden local symmetry is introduced, masslessness and coupling universality of dynamically generated gauge boson are ensured. To illustrate these ideas we take a four dimensional Grassmannian sigma model as an example and show that the model should be regarded as a cut-off theory and there is a critical coupling at which the hidden local symmetry is restored. Propagator and vertex functions of the gauge field are calculated explicitly and existence of the massless pole is shown. The beta function determined from the $ Z $ factor of the dynamically generated gauge boson coincides with that of an asymptotic nonfree elementary gauge theory. Using these theoretical machinery we construct a model in which asymptotic free and nonfree gauge bosons coexist and their running couplings are related by the reciprocally proportional relation.

hep-th↗

arXiv1996

Solvable Optimal Velocity Models and Asymptotic Trajectory

In the Optimal Velocity Model proposed as a new version of Car Following Model, it has been found that a congested flow is generated spontaneously from a homogeneous flow for a certain range of the traffic density. A well-established congested flow obtained in a numerical simulation shows a remarkable repetitive property such that the velocity of a vehicle evolves exactly in the same way as that of its preceding one except a time delay $T$. This leads to a global pattern formation in time development of vehicles' motion, and gives rise to a closed trajectory on $Δx$-$v$ (headway-velocity) plane connecting congested and free flow points. To obtain the closed trajectory analytically, we propose a new approach to the pattern formation, which makes it possible to reduce the coupled car following equations to a single difference-differential equation (Rondo equation). To demonstrate our approach, we employ a class of linear models which are exactly solvable. We also introduce the concept of ``asymptotic trajectory'' to determine $T$ and $v_B$ (the backward velocity of the pattern), the global parameters associated with vehicles' collective motion in a congested flow, in terms of parameters such as the sensitivity $a$, which appeared in the original coupled equations.

patt-sol↗