Ma Wei-hsing

The non-analog double charge exchange transition: 16O(π+, π−)16Ne(g.s.) and 12C(π+, π−)12O(g.s.)

Abstract Six possible successive two-delta excitation mechanisms for pion-induced non-analog double charge exchange transition on the targets 16 O and 12 C are suggested. In the framework of the model proposed here the angular distributions of 164 MeV for 12 C and 120, 164 and 200 MeV for 16 O have been evaluated and compared with the existing data. Our results are in good agreement with experimental data available, and strongly indicate that the non-analog transitions 16 O(π + , π − ) 16 N e(g.s.) and 12 C (π + , π − ) 12 O (g.s) proceed basically through the double delta isobar excitation on a nucleon, and the dominant process is the so-called successive Δ mechanism.

The hybrid quark-hadron model for three-body systems ☆

Abstract Our calculations within the hybrid quark-hadron model of the magnetic form factors of the three-nucleon systems are given. Three-nucleon form factors for 0≤ q 2 ≤4(GeV/ c ) 2 are discussed. Striking six-quark cluster effects are found, with the probability for a nucleon to be in a six-quark cluster about 14%. Needed theoretical improvements in the model are also discussed.

NN annihilation effect in elastic\(\bar p\)-nucleus scattering

SummaryThe effect ofNN annihilation on antiproton-nucleus scattering has been studied by use of phenomenologicalNN annihilation potential. The results indicate that at small angle the effect makes no difference but for large angles it plays an important role in solving the discrepancies between theory and existing data available.RiassuntoSi è studiato l’effetto dell’annichilazione diNN sullo scattering tra antiprotone-nucleo con l’uso del potenziale di annichilazione diNN fenomenologica. I risultati indicano che ad un angolo ridotto l’effetto non fa alcuna differenza, ma per angoli ampi gioca un ruolo importante nel risolvere le discrepanze tra la teoria e i dati disponibili esistenti.РезюмеИспользуя феноменологический потенциалNN аннигиляции, исследуется влияниеNN аннигиляции на рассеяния антипротонов на ядрах. Полученный результат показывает, что при малых углах эффект пренебрежимо мал, а при больших углах играет важную роль в обьяснении расхождений между теорией и имеющимися экспериментальными данными.

Multiquark cluster effect in a three-body system

Abstract The charge density of 3He was calculated in the hybrid quark-hadron model. The results clearly show that the multiquark cluster effect in 3He is most likely responsible for the observed central “hole” of 3He charge density.

Elastic 4He + 4He scattering in the hybrid quark-hadron model☆

Abstract A calculation of alpha-alpha scattering at higher energy has been performed in the hybrid quark-hadron model. The results show that the quark degrees of freedom play an important role in explaining available experimental data.

Composite particle scattering in a hybrid quark-hadron model

Abstract We propose a hybrid quark-hadron model to describe high-energy composite particle scattering. Parameters for the quark sector in the model are determined by fitting pp scattering data. We apply the model without any free parameter to proton-alpha elastic scattering. Our model yields a quite large improvement over various calculations done before and provides a very good agreement with existing available data. Our results also show that the quark degrees of freedom in NN interaction play an important role in improving theoretical description of experimental data and must be included in future calculations.

Spin-dependent structure function of deuteron

Based on the relationship between electron deep inelastic Scattering and forward virtual photon Compton scattering, and using the information provided by virtual photon absorption on target, we study spin-dependent structure function of deuteron and its corresponding first moment, which are expressed by total absorption cross sections of virtual photon. The absorption cross section is determined by helicity amplitudes A(1/2) and A(3/2) which are evaluated in SU(6) quark model with an improved electromagnetic interaction. The method avoids the difficulty for solving nonperturbative QCD which is impossible at present. In general, our theoretical predictions on the first moment and quark polarization in deuteron are in good agreement with data of E143 at SLAG, EMC at CERN and Hermes at DESY.

Antiproton-carbon inelastic scattering and\(\overline N N\) annihilation effectsannihilation effects

SummaryThe differential cross-sections of inelastic scattering for antiprotons by12C at incident momentumPlab=600 MeV/c are calculated on the basis of Glaubers multiple scattering theory and the distorted wave impulse approximation and by use of the transition densities obtained from fitting to the electron scattering data and the elementary two-body amplitudes.

Nucleon Properties in a Quark Bag Model With Woods-Saxon Type Confining Potential

\overline N N