Masami Nakagawa

On Selection Rule of Weak Processes and Decays of New Particles. II

Following a previous paper, we propose s~lection rules for weak processes. The first rule is .1n1=0, where n,=n+n; n(n) indicates an (anti-)urbaryon number. The second rule is that a dimensionality of the SU(3) representation of hadronic system is conserved along sor t-channel dependig on the parity property. These rules are applied to decay processes of new hadrons,_an indication of which has -been observed in a cosmic ray jet. We further attempt some conjectures on the second event that has recently been reported.

Gauge interaction of baryons in hidden local symmetry

SummaryThe hidden local symmetry of the non-linear sigma model is extended to include baryons. In two papers (M. Bando, T. Kugo and Y. Yamawaki:Phys. Rep.,164, 217 (1988);Prog. Theor. Phys.,73, 1541 (1985)), the low-energy theorems for mesons were successfully reproduced. It seems important to investigate whether some kind of the low-energy theorems for baryons holds in the same framework. Indeed, theS-wave pion-nucleon scattering lengths, the conserved vector currents (CVC) of β-decays of baryons and Sakurais scenario of the electromagnetic interactions of hadrons are all reproduced. Our interaction Lagrangians are stable under the small variation of each vertex. Thus, they deserve the effective one.

Chiral symmetry breaking in hidden local symmetry

SummaryChiral breaking for baryon and meson interaction is formulated in the framework of the hidden local symmetric theory of the non-linear sigma model on the manifoldU(3)L×U(3)R/U(3)V. The chiral symmetry-breaking term transforms as (3,3*) underU(3)L×U(3)R at the first order. Several low-energy theorems are derived for the electromagnetic interaction of baryon. The symmetry-breaking term preservesSU(2)×U(1) symmetry; we have confirmed that the Sakurai formula of the electromagnetic interaction of vector meson holds and directly shown that the photon mass vanishes. The fundamental gauge coupling constantg and the mixing angle θ of vector meson are fixed by independent phenomena of vector meson masses and eē decay of vector meson. Using these values ofg and θ, we extend our analysis to the nucleon form factor and indicate a breaking of the OZI rule and a sizable contents of s-quark pair in the nucleon.

Implications of Four-Quark Scalar Mesons with Charm

The possibility of the existence of four-quark scalar mesons with charm 15+( cuud) and 15°( cd ud) is studied in the framework of 5 U( 6 )cs, a combined symmetry of color and spin, with a binding potential due to a gluon magnetic interaction. We observe that the masses of the mesons range from 1.8 Ge V to 2.4 Ge V and that the mesons are produced dominantly in the forward region by neutrino reactions. If the masses of 15 were smaller than mD+ m~, the mesons will be stable and the lifetimes will be the same order in magnitude with those of D mesons. Thus detection of a dual structure in mass and lifetime for charmed mesons, and of a decay 15--> D+2r with an appreciable (at least a few percent) branching ratio will provide a confirmation of the existence of the four-quark scalar mesons.

Nucleon electromagnetic form factors in hidden local symmetry theory

SummaryIn previous papers (Nuovo Cimento A,108 (1995) 241, 1051), the hidden local symmetry of the chiral theory based on the non-linear sigma-model on the manifoldU(3)L×U(3)R/U(3)V was extended to the baryon interaction and shown to reproduce well the low-energy theorems. Introducing anSU(3) breaking in the theory, the mass formula and the Sakurai formula of the electromagnetic interaction of vector mesons are obtained consistently. In this paper, by introducing the effective tensor interactions of orderO(p2), the magnetic form factor of the nucleon is analysed as well as the electric form factor, partly done in the previous papers, and a breaking of the OZI rule and a sizeable content of s-quark pair in both the electric and magnetic form factors of the nucleon are indicated again.