We introduce the polarized valon distributions to describe the spin dependence of parton distributions.The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to ob...We introduce the polarized valon distributions to describe the spin dependence of parton distributions.The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to obtain polarized parton distribution in a proton. In order to be able to obtain the spin contribution of sea quarks, we need to improve the valon model We employ the Bernstein polynomial averages to obtain the unknown parameters which exist in our calculations. Our results for the polarized proton structure function, xg1p, are in good agreement with the experimental data for some values of Q2.展开更多
Exclusive decays J/ψ(ψ') → Y(Y-) (Y = A,∑0, -) are studied in the quark model by combining thestructure of hyperons in the transition. The branching ratios are evaluated contrastively by adopting different hyp...Exclusive decays J/ψ(ψ') → Y(Y-) (Y = A,∑0, -) are studied in the quark model by combining thestructure of hyperons in the transition. The branching ratios are evaluated contrastively by adopting different hyperonwavefunctions, SU(6) basis, and uds basis, which account for SU(3)f breaking, and the results show that the differentdescription of quark mass breaking plays an important role in the evaluation of the decay width for processes J/ψ(ψ') →Y(Y-).展开更多
Calculations of helicity amplitudes for the low-lying nucleon resonances are displayed based on a non-relativistic constituent quark model with a harmonic oscillator confinement. The explicit effect of quark confinem...Calculations of helicity amplitudes for the low-lying nucleon resonances are displayed based on a non-relativistic constituent quark model with a harmonic oscillator confinement. The explicit effect of quark confinement is shown. Our results show that the effect plays sizable role on some transition amplitudes of S11 (1535) and D13(1520) resonances. The effect on the △(1232) transition amplitudes is less than 10%. However, the effect on the Roper resonance is remarkable but is inconclusive.展开更多
The instanton induced cross section in deep inelastic kinematics is a subject which people are tendentious to investigate it. Instanton induced contributions are well defined for the nucleon structure function. The no...The instanton induced cross section in deep inelastic kinematics is a subject which people are tendentious to investigate it. Instanton induced contributions are well defined for the nucleon structure function. The non-perturbative contribution to the quark distributions of structure function, F2 (x, Q2 ), is considered within an instanton model for the QCD vacuum. We find that the structure function may possess numerically large non-perterbative contributions which are related to the violation of chirality and correspond to the correction of parton distribution of the leading twist. It is shown that the instantons give a negative contribution to the structure function at the NLO approximation. A comparison between our results, considering instantaon effect, and the case when we do not take this effect is done. Taking into account the instanton size, ρ, via the modified running coupling constant we get to a good agreement between our results at the NLO and NNLO approximations and the available experimental data, specially at the low values of the Bjorken variable x<0.1 which confirms the validity of our calculations.展开更多
文摘We introduce the polarized valon distributions to describe the spin dependence of parton distributions.The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to obtain polarized parton distribution in a proton. In order to be able to obtain the spin contribution of sea quarks, we need to improve the valon model We employ the Bernstein polynomial averages to obtain the unknown parameters which exist in our calculations. Our results for the polarized proton structure function, xg1p, are in good agreement with the experimental data for some values of Q2.
文摘Exclusive decays J/ψ(ψ') → Y(Y-) (Y = A,∑0, -) are studied in the quark model by combining thestructure of hyperons in the transition. The branching ratios are evaluated contrastively by adopting different hyperonwavefunctions, SU(6) basis, and uds basis, which account for SU(3)f breaking, and the results show that the differentdescription of quark mass breaking plays an important role in the evaluation of the decay width for processes J/ψ(ψ') →Y(Y-).
文摘Calculations of helicity amplitudes for the low-lying nucleon resonances are displayed based on a non-relativistic constituent quark model with a harmonic oscillator confinement. The explicit effect of quark confinement is shown. Our results show that the effect plays sizable role on some transition amplitudes of S11 (1535) and D13(1520) resonances. The effect on the △(1232) transition amplitudes is less than 10%. However, the effect on the Roper resonance is remarkable but is inconclusive.
文摘The instanton induced cross section in deep inelastic kinematics is a subject which people are tendentious to investigate it. Instanton induced contributions are well defined for the nucleon structure function. The non-perturbative contribution to the quark distributions of structure function, F2 (x, Q2 ), is considered within an instanton model for the QCD vacuum. We find that the structure function may possess numerically large non-perterbative contributions which are related to the violation of chirality and correspond to the correction of parton distribution of the leading twist. It is shown that the instantons give a negative contribution to the structure function at the NLO approximation. A comparison between our results, considering instantaon effect, and the case when we do not take this effect is done. Taking into account the instanton size, ρ, via the modified running coupling constant we get to a good agreement between our results at the NLO and NNLO approximations and the available experimental data, specially at the low values of the Bjorken variable x<0.1 which confirms the validity of our calculations.
