Koichi Yamawaki

On the Vector Mesons as Dynamical Gauge Bosons of Hidden Local Symmetries

We obtain the KSRF relation, gϱ/gϱππ = 2ƒπ2, as a “low-energy theorem” of the hidden local symmetry in the U(3)L × U(3)R/U(3)v nonlinear sigma model, which proves to be clear evidence of vector mesons being dynamical gauge bosons of the hidden local symmetry. U(3)1 × U(3)R breaking are also discussed, leading to successful relations: gϱ/mϱ2 = 3gω/mω2 = −√123gφ /mφ2=1/g and mφ/mK∗=mK∗/mω=mK∗/mϱ. We further show that it is formally possible to extend the hidden local symmetry so as to incorporate the axial-vector mesons.

The Problem of P+ = 0 Mode in the Null-Plane Field Theory and Dirac's Method of Quantization

The null-plane quantization is studied with the emphasis on the P+=O mode, by using Diracs quantization for constrained systems. This mode is eliminated from the Hilbert space and the physical vacuum can be defined in a kinematical way. It enables us to conxad struct the physical Fock space kinematically. Poincare invariance is also studied in detail.

A consistent formulation of the null-plane quantum field theory

Abstract It is shown in the usual framework of quantum field theory that the null-plane restriction of a field operator is not a well-defined operator-valued distribution. The cause of the trouble is the so-called P + = 0 mode; in order to make it harmless, it is almost inevitable to violate Lorentz invariance. A consistent formulation of the null-plane quantization, which is supposed to be the simplest possible one, is proposed by modifying the definition of Poisson brackets. This theory is invariant under a Poincare subalgebra containing seven generators. It is also shown that the absence of vacuum polarization is realized consistently in this formalism.

QUARK-ORBITAL REGGE TRAJECTORIES.

It is shown that the pattern of Regge trajectories of hadrons becomes very much simpler and more regular than the usual Chew-Frautschi plot when one uses the orbital angular moxad mentum of the quarks in a hadron instead of the spin of the meson and the spin minus 1/2 of the baryon, as the Reggeized angular momentum. Available data on particles and resonances are classified by means of the quark-orbital Regge trajectories, and as a result of it, the following pattern appears: there are linear rising quark-orbital trajectories with the universal slope for each irreducible representation of SU(6); actual hadron spectra are reproduced by adding the spin- and unitary spin-exchange interactions and the mass shift of the .l-quark. The Gell-Mann-Okubo mass formula holds rather good including resonances with high mass. Effects of the spin-orbit interaction are clearly recognized and its magnitude is nearly of the same order as those of the spin- and unitary spin-exchange interactions for mesons, whereas they are not so obvious for baryons. It follows from this splitting pattern of the quark-orbital Regge trajectories that the exchange degeneracies hold better for mesons than for baryons and that many parity doublets exist apparently and several parity partners should not appear, in conformity with experimental data. Classification of resonances using the orbital angular momentum between incoming two hadrons does not show much regularity. It is suggested from these results that strong interactions are essentially characterized by the degree of freedom of the spatial motion at the urbaryon level. § I. Introduction The fact that the hadron spectra obey the classification due to SU(6) @0 (3) very well*l and that the properties of the exotic and nonexotic channels are quite different, seems to show the importance of pursuing seriously the consequences of the quark model. On the other hand, we also recognize the importance of analytic properties of amplitudes, especially the Regge trajectories. Then the following question arises naturally: Which is the most important quantity that essentially determines the dynamics of strong interactions: the three angular momenta, total angular momentum of a hadron (denoted by J in the following), total orbital angular momentum of a hadron in the quark model (denoted by L) or the total orbital angular momentum of hadrons in the most dominant decay mode of the hadron (denoted by l)? It is the purpose of this paper to shed some light on this question by a comprehensive investigation of experimental data on hadron spectra. We will discuss the classification of mesons and baryons in the quark model in § 2 and *> This does not necessarily mean that the SU(6) symmetry applies to the wholeS-matrix as

Flavor-singlet spectrum in multi-flavor QCD

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

Walking signals in eight-flavor QCD on the lattice

We investigate walking signals of Nf = 8 QCD through the meson spectrum, using the HISQ action. Our data for Nf = 8 QCD are consistent with chiral perturbation theory (ChPT) in their chiral extrapolations, hence with the theory exhibiting spontaneous chiral symmetry breaking. Remarkably, while the Nf = 8 data near the chiral limit are well described by the ChPT, those for the relatively large fermion bare mass mf away from the chiral limit actually exhibit a finite-size hyperscaling relation, suggesting a large anomalous dimension g m � 1. This implies that there exists a remnant of the infrared conformality, and suggests that a typical “one-family technicolor model, as modeled by Nf = 8 QCD, can be a walking technicolor theory.

The KMI Lattice Project — Exploring for Technicolor from QCD

It is well known that the SU(3) gauge theory with the fundamental 16-flavor fermion is governed by a nontrivial infrared fixed point in the 2-loop perturbation theory, while the theory has not been well investigated by non-perturbative lattice simulations. We investigate properties of 16-flavor QCD by lattice simulation with highly improved action setup(HISQ/tree) at two lattice spacings. We present preliminary results for the mass of the lightest pseudoscalar meson, and its decay constant at non-zero fermion mass. We discuss the finitemass and finite-volume scaling of the quantities, the mass anomalous dimension extracted from the scaling, and comparison of the anomalous dimension with the perturbation theory.

KMI project on many flavor QCD with N_f=12 and 16

Information of the phase structure of many flavor SU(3) gauge theory is of great interest for finding a theory which dynamically breaks the electro-weak symmetry. We study the SU(3) gauge theory with fermions for

Duality Constraints and Representation Mixings in Light-Like Chiral Algebra

N_f=12

Lattice Study of SU(3) Gauge Theory with Four Fundamental Fermions

and 16 in fundamental representation. Both of them, through perturbation theory, reside in the conformal phase. We try to determine the phase of each theory non-perturbatively with lattice simulation and to find the characteristic behavior of the physical quantities in the phase. HISQ type staggered fermions are used to reduce the discretization error which could compromise the behavior of the physical quantity to determine the phase structure at non-zero lattice spacings. Spectral quantities such as bound state masses of meson channel and meson decay constants are investigated with careful finite volume analysis. Our data favor the conformal over chiral symmetry breaking scenario for both