Shin-ichi Nakariki

An exact solution in Poincaré gauge theory : monopole solution

Poincare gauge theory is treated such that a translational gauge field is actually identified with the Einstein’s gravitational field and the Lorentz gauge field is thought of as a pair of Yang–Mills‐like field and its partner. An exact solution is investigated in this model, which is similar to the Wu–Yang solution in Yang–Mills theory. As a result, a solution is found. According to Kalb’s ansatz, the ‘‘Yang–Mills parts’’ of the solution are interpreted as ‘‘electric’’ and ‘‘magnetic’’ fields that are created by a point source with a unit ‘‘magnetic’’ charge and a certain ‘‘electric’’ charge. The translational gauge field then gives the Reissner–Nordstrom space‐time.

MULTI-CHAIN MODEL WITH SUCCESSIVE COLLISION AND HIGH-ENERGY NUCLEUS–NUCLEUS COLLISIONS

High-energy nucleus–nucleus collisions are studied in the multi-chain model with successive collision. Analytic forms for the longitudinal momentum distribution of the inclusive reaction are discussed. It is shown that the longitudinal momentum distribution in nucleus–nucleus collisions is expressed in the Glauber probability with the hypergeometric distribution.

ANTI-HYPERON POLARIZATION IN pA AND Σ-A COLLISIONS AND INTRINSIC ANTIDIQUARK STATE IN INCIDENT BARYON

We discuss the relation between the polarization of inclusively produced (anti)hyperons and the incident baryon states in the framework of the constituent quark–diquark cascade model. We assume that there is an intrinsic diquark–antidiquark state in the incident baryon, in which the intrinsic diquark immediately fragments into a non-leading baryon and the antidiquark behaves as a valence constituent. It is also assumed that the valence (anti)diquark in the incident nucleon tends to combine selectively with a spin-down sea quark and, on the other hand, the spin-up valence quark in the projectile is chosen by a sea (anti)diquark in preference to the spin-down valence quark. It is found that the incident spin-1/2 baryon is mainly composed of a spin-0 valence diquark and a valence quark, and contains an intrinsic diquark–antidiquark state with a probability of about 7%.

Hyperon polarization in quark-diquark cascade model

We relate the hyperon polarizations in proton-proton and proton-nucleus collisions to the leading particle effect and use the constituent quark-diquark cascade model with SU(6) wave function. We assume that the quantization axis is characterized by the production normal of the leading baryon of the most massive cascade chain and the incident valence diquark tends to pick up a spin down sea quark or conversely a sea diquark preferentially combines with the spin up incident valence quark to form a leading baryon as compared with the spin down valence quark.

Charmed hadron production in

We investigate the meson, baryon and anti-baryon productions in \pi p and Kp collisions in terms of a constituent cascade model which includes charm flavour. The constituent diquark in an incident baryon has a tendency to get a large momentum fraction, resulting in considerable difference of subenergies for particle productions from quark-diquark and quark-antiquark chains in a meson-baryon collision. As a consequence, the leading particle effects on D meson productions are expected to be quite different in \pi+ and \pi- beams at present accelerator energies.