Byung Geel Yu

Coulomb sum rule in the quasielastic region

Within a relativistic single particle model, we calculate the Coulomb sum rule of inclusive electron scattering from {sup 40}Ca and {sup 208}Pb in the quasielastic region. Theoretical longitudinal and transverse structure functions are extracted for three-momentum transfers from 300 to 500 MeV/c and compared with the experimental data measured at Bates and Saclay. We find that there is no drastic suppression of the longitudinal structure function and that the Coulomb sum rule depends on the nucleus in our theoretical model.

Evidence for the tensor meson exchange in the kaon photoproduction

Abstract The contribution of the tensor meson K 2 ⁎ ( 1430 ) exchange in the process γ p → K + Λ ( Σ 0 ) is investigated within the Regge framework. Inclusion of the K 2 ⁎ exchange in the K ( 494 ) + K ⁎ ( 892 ) exchanges with the coupling constants chosen from the SU(3) symmetry leads to a better description of the production mechanism without referring to any fitting procedure. This shows the significance of the role of the tensor meson exchange to have the Regge theory basically free of parameters with the SU(3) symmetry a good approximation for the meson–baryon couplings.

Effect of strangeness for neutrino (antineutrino) scattering in the quasi-elastic region

We present the neutral- and charged-current reactions by incident neutrino (antineutrino) scattering on the nucleon and on the {sup 12}C target in the quasi-elastic region within the framework of a relativistic single-particle model. The incident energies at 500 MeV and 1 GeV are used for the scattering. Effects of strangeness are studied thoroughly on the cross sections, the ratios between the neutral- and charged-current reactions, and the asymmetries by incident neutrino and antineutrino. We find that there exists some cancellation of the strange quark contributions between the knocked-out protons and neutrons in the neutrino (antineutrino)-nucleus scattering. The effect of strangeness is exhibited more strongly on the asymmetry than on the ratio or cross section. On a difference of the asymmetry, the effect of strangeness appears strongly, but on a summation of the asymmetry, the effect almost disappears in the low and middle kinetic energies of the knocked-out nucleon.

The neutral-current neutrino-nucleus scattering in the quasielastic region

The neutral-current neutrino-nucleus scattering is calculated through the neutrino-induced knocked-out nucleon process in the quasielastic region by using a relativistic single particle model for the bound and continuum states. The incident energy range between 500 MeV and 1.0 GeV is used for the neutrino (antineutrino) scattering on the 12C target nucleus. The effects of the final state interaction of the knocked-out nucleon are studied not only on the cross section but also on the asymmetry due to the difference between neutrinos and antineutrinos, within a relativistic optical potential. We also investigate the sensitivity of the strange quark contents in the nucleon on the asymmetry.

The Electric Dipole Amplitudes of the Neutral Pion Photoproduction on the Proton near Threshold

The electric dipole amplitude E 0+ for p (γ, π 0 ) p near threshold has been extracted from the experimental data by fitting the total cross section in high energy region, E γ >160 MeV. The result is (-1.56±0.10)×10 -3 m π+ -1 . This amplitude is calculated by taking the vector mesons into account in the pole model of t-channel. Our analysis manifests a favor of negative sign for the ρπγ coupling constant.

Strangeness for Neutrino-Nucleus Scattering in Quasielastic Region

Within the framework of a relativistic single particle model we calculate neutral- and charged-current reactions for the neutrino scattering on 12 C and 16 O in quasielastic region. In the intermediate neutrino energy (500 MeV), we develop several ways to investigate effects of the strangeness, such as ratios of proton to neutron for neutral-current reaction, ratios of the neutral- to charged-current reactions, and asymmetries by incident neutrino and antineutrino. A cancellation mechanism of the strangeness effects in the nuclei was found to lead to indiscernible strangeness effects on the relevant cross sections. Consequently, the strangeness effects on the asymmetries and ratios are more feasible tools of looking for the strangeness effects rather than those on the cross section. These phenomena are shown to be nearly independent of the target nuclei exploited in this calculation.

Pion and proton form factors in the regge description of electroproduction p(e, e′π+)n

Electroproduction of π+ above the resonance region is analyzed in the Regge model for π + ρ exchanges. The importance of the roles of the pion and the proton form factors in the process is discussed in comparison with the existing models of Kaskulov and Mosel and of Vrancx and Ryckebusch. The present model with a proton form factor of a simple dipole-type is shown to yield a better description of DESY and JLab data over those models for the high Q2 and −t region up to 5 GeV2.

EFFECT OF STRANGENESS FOR NEUTRINO-NUCLEON AND NEUTRINO-NUCLEUS SCATTERING IN QUASIELASTIC REGION

We present the neutral-current (NC) and charged-current (CC) reactions by incident neutrino (antineutrino) scattering on the nucleon, and also on the 12C target in quasi-elastic region within the framework of a relativistic single particle model. Effects of the strangeness are studied on the cross sections, the ratios between the NC and CC reactions, and the asymmetries. We found that there exists some cancellation of the strange quark contributions between the knocked-out protons and neutrons in the neutrino (antineutrino)-nucleus scattering. The effect of the strangeness on the asymmetry exhibits larger than that on the ratio and the cross section.