124556870
A New Effect in the QCD Fusion of Nuclear Partons
The parton fusion in nucleus at the leading order of recombination is investigated based on perturbative QCD. We compute various cut diagrams including the nuclear parton fusion, and find that the parton-fusion effects depend on the nuclear QCD structure.
124870414
Antishadowing Corrections in the Evolution Equation of Quark Distributions
We introduce the antishadowing effect to restore the momentum sum rule in the quantum chromodynamics evolution equation for quarks in small x region.
122906986
Nuclear shadowing in the constituent quark model
The shadowing phenomenon is discussed within the framework of the constituent quark model incorporating the gluon recombination mechanism. The Qiu shadowing factor reflects the correct behaviour for the sea quark density for very small values of x. However, for larger x it is necessary to take nuclear antishadowing into account.
18244927
Nuclear Shadowing and Antishadowing in a Unitarized BFKL Equation
The nuclear shadowing and antishadowing effects are explained by a unitarized BFKL equation. The Q2and x-variations of the nuclear parton distributions are detailed based on the level of the unintegrated gluon distribution. In particular, the asymptotical behavior of the unintegrated gluon distribution near the saturation limit in nuclear targets is studied. Our results in the nuclear targets are insensitive to the input distributions if the parameters are fixed by the data of a free proton. PACS numbers: 13.60.Hb; 12.38.Bx. keywords: nuclear shadowing and antishadowing; unintegrated gluon distribution in nuclei; QCD evolution equation Supported by National Natural Science Foundation of China 10135060, 10475028 and 10205004. Corresponding author, E-mail: weizhu @mail.ecnu.edu.cn
14042487
Prediction for unintegrated parton distributions
Unintegrated parton distributions in the proton and nucleus are predicted by a modified Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) equation incorporating the shadowing corrections, which include exact energy-momentum conservation in each splitting and fusion vertices. We find that the nuclear shadowing effects are obvious, although they are far from the saturation limit. On the other hand, we point out that the suppression of the unintegrated gluon distribution toward lower k{sub t}{sup 2} may arise from the valence-like input rather than the saturation effects.
122365434
Bag skin effect for Friedberg-Lee model
Importance of the bag skin effect to determine the parameters of the Friedberg-Lee model is pointed out. The European Muon Collaboration (EMC) effect regarded as a bag skin effect can be used to determine the parameters of this model.
14637708
Factorization and polarization in two charmed-meson B decays
We provide a comprehensive test of factorization in the heavy–heavy B decays motivated by the recent experimental data from the BELLE and BABAR collaborations. The penguin effects are not negligible in the B decays with two pseudoscalar mesons. The direct CP asymmetries are found to be a few percent. We give estimates on the weak annihilation contributions by analogy to the observed annihilation-dominated processes. The Nc insensitivity of branching ratios indicates that the soft final state interactions are not dominant. We also study the polarizations in B→D*D(s)* decays. The power law shows that the transverse perpendicular polarization fraction is small. The effects of the heavy quark symmetry breaking caused by the perturbative QCD and power corrections on the transverse polarization are also investigated.
119155459
Neutrino decay as a possible interpretation of the MiniBooNE observation with unparticle scenario
In a new measurement on neutrino oscillations, νμ→νe, the MiniBooNE Collaboration observes an excess of electron-like events at low energy and the phenomenon may demand an explanation that obviously is beyond the oscillation picture. We propose that the heavier neutrino, ν2, decaying into a lighter one, ν1, via the transition process νμ→νe+X, where X denotes any light products, could be a natural mechanism. The theoretical model we employ here is the unparticle scenario established by Georgi. We have studied two particular modes $\nu_{\mu}\to\nu_{e}+\mathcal{U}$ and νμ→νe+ν̄e+νe. Unfortunately, the number coming out of the computation is too small to explain the observation. Moreover, our results are consistent with the cosmology constraint on the neutrino life time and the theoretical estimation made by other groups; therefore, we can conclude that even though neutrino decay seems plausible in this case, it indeed cannot be the source of the peak at lower energy observed by the MiniBooNE Collaboration and there should be other mechanisms responsible for the phenomenon.
121153627
Properties and structure of N = Z nuclei within relativistic mean field theory
The axially deformed relativistic mean field theory with the force NLSH has been performed in the blocked BCS approximation to investigate the properties and structure of N = Z nuclei from Z = 20 to Z = 48. Some ground state quantities such as binding energies, quadrupole deformations, one/two-nucleon separation energies, root-mean-square (rms) radii of charge and neutron, and shell gaps have been calculated. The results suggest that large deformations can be found in medium-heavy nuclei with N = Z = 38–42. The charge and neutron rms radii increase rapidly beyond the magic number N = Z = 28 until Z = 42 with increasing nucleon number, which is similar to isotope shift, yet beyond Z = 42, they decrease dramatically as the structure changes greatly from Z = 42 to Z = 43. The evolution of shell gaps with proton number Z can be clearly observed. Besides the appearance of possible new shell closures, some conventional shell closures have been found to disappear in some region. In addition, we found that the Coulomb interaction is not strong enough to breakdown the shell structure of protons in the current region.
122812048
Nucleon effective mass in symmetric nuclear matter from the extended Brueckner- Hartree-Fock approach *
We have calculated the nucleon effective mass in symmetric nuclear matter within the framework of the Brueckner-Bethe-Goldstone (BBG) theory, which has been extended to include both the contributions from the ground-state correlation effect and the three-body force (TBF) rearrangement effect. The effective mass is predicted by including the ground-state correlation effect and the TBF rearrangement effect, and we discuss the momentum dependence and the density dependence of the effective mass. It is shown that the effect of ground state correlations plays an important role at low densities, while the TBF-induced rearrangement effect becomes predominant at high densities.
122147995
Hyperon–hyperon interaction in relativistic mean field model
By using the new experimental data of �� potential, this paper has performed a full calculation for strange hadronic matter with different strangeness contents as well as its consequences on the global properties of neutron star matter in relativistic mean field model. It finds that the new weak hyperon–hyperon interaction makes the equations of state much stiffer than the result of the previous strong hyperon–hyperon interaction, and even stiffer than the result without consideration of hyperon–hyperon interaction. This new hyperon–hyperon interaction results in a maximum mass of 1.75M⊙ (where M⊙ stands for the mass of the Sun), about 0.2–0.5M⊙ larger than the previous prediction with the presence of hyperons. After examining carefully the onset densities of kaon condensation it finds that this new weak version of hyperon–hyperon interaction favours the occurrence of kaons in comparison with the strong one.