121047651
A More Restrictive Upper Bound for the Bare Pomeron Intercept
By studying the properties of the modified Gribov-Levin-Ryskin evolution equation which incorporates both shadowing and antishadowing effects, the more restrict upper bound is set for the bare pomeron intercept in the case when gluons uniformly distribute within the proton.
124473583
Partonic Structure of the Pomeron in the Modified GLR Equation
The gluon recombination effect in the pomeron is studied by using the modified Gribov–Levin–Ryskin evolution equation. We find that the measured parton distributions in the pomeron can be generated dynamically from a purely gluonic input on assuming a small size for the pomeron.
119716730
A twist-4 effect in the parton evolution processes
Recently, a research group reported that they can fit the F2 data well by using the Altarelli-Parisi evolution equation with a valence-like initial gluon distribution, which means that we need not consider the high twist effects in the proton. In this letter, we point out that their valence-like initial gluon distribution is unreasonable for the proton structure function. With the reasonable initial distributions, we find that the high twist corrections to the Altarelli-Parisi evolution equation is necessary.
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.
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
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.
123012350
Phenomenological study of Sudakov effects in the pion form factor
The pion electromagnetic form factor with leading and next-to-leading twist corrections is studied in the framework of the pQCD approach. We find that the Sudakov effects provide a weak suppression of the nonperturbative contributions at the experimental accessible energy region. We also find a large twist-3 contribution. Our conclusion is that the prediction of the pion form factor in the pQCD approach is not precise.
204011866
Effect of tensor force on the density dependence of symmetry energy within the BHF framework
The effect of tensor force on the density dependence of nuclear symmetry energy has been investigated within the framework of the Brueckner-Hartree-Fock (BHF) approach. It is shown that the tensor force manifests its effect via the tensor 3SD1 channel. The density dependence of symmetry energy Esym turns out to be determined essentially by the tensor force from the π meson and ρ meson exchanges via the 3SD1 coupled channel. Increasing the strength of the tensor component due to the ρ-meson exchange tends to enhance the repulsion of the equation of state of symmetric nuclear matter and leads to the reduction of symmetry energy. The present results confirm the dominant role played by the tensor force in determining nuclear symmetry energy and its density dependence within the microscopic BHF framework.
122313362
Hyperon coupling dependence of hadron matter properties in relativistic mean field model
The properties of hadronic matter at β equilibrium in a wide range of densities are described by appropriate equations of state in the framework of the relativistic mean field model. Strange meson fields, namely the scalar meson field σ* (975) and the vector meson field (1020), are included in the present work. We discuss and compare the results of the equation of state, nucleon effective mass, and strangeness fraction obtained by adopting the TM1, TMA, and GL parameter sets for nuclear sector and three different choices for the hyperon couplings. We find that the parameter set TM1 favours the onset of hyperons most, while at high densities the GL parameter set leads to the most hyperon-rich matter. For a certain parameter set (e.g. TM1), the most hyperon-rich matter is obtained for the hyperon potential model. The influence of the hyperon couplings on the effective mass of nucleon, is much weaker than that on the nucleon parameter set. The nonstrange mesons dominate essentially the global properties of dense hyperon matter. The hyperon potential model predicts the lowest value of the neutron star maximum mass of about 1.45 Msun to be 0.4-0.5 Msun lower than the prediction by using the other choices for hyperon couplings.
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.
116907310
A solution to Higgs naturalness
The Standard Model (SM) is usually considered to be unnatural because the scalar Higgs mass receives a quadratic divergent correction. We suggest a new way to solve the naturalness problem from point of view of renormalization group method. Our approach is illustrated through the familiar $\phi^4$ theory. A renormalization group equation for scalar field mass is proposed by introducing a subtraction scale. We give a non-trivial prediction: the Higss mass at short-distance is a damping exponential function of the energy scale. It follows from a characteristic of the SM that the couplings to Higgs are proportional to field masses, in particular the Higgs self-interactions. In the ultraviolent limit, the Higgs mass approaches to a mass called by Veltman mass which is at the order of the electroweak scale. The fine-tuning is not necessary. The Higgs naturalness problem is solved by radiative corrections themselves.