Monopole Excitation of the Nucleon in a Relativistic Three-Quark Model

The densities and form factors of the proton andthe Roper monopole excitedstate resonance are calculatedusing a relativistic three-quark model. Small currentquark masses are used with the three-body Dirac equation solved in hypercentralapproximation. A QCD-based three-body potential,proportional to a minimum string length between thethree quarks, is used for confinement. The calculatedelectric form factor for the proton reproduces closelya dipole fit to the data. The proton density is morecompact than is the Roper resonance density. The centraldensity of the proton is about five times that for the Roper resonance. The hyperradial nodein the Roper resonance composite three-quark wavefunction shows up as a node in the transition densitybetween the proton and the Roper resonance. This node also causes the calculated transition formfactor to be larger than either the proton or Roperresonance form factors, all evaluated at the same valueof momentum transfer. The Roper resonance form factor is smaller than the proton form factor, asexpected, indicative of the Roper resonance being a morediffuse system than the proton.     

Baryon Structure in AdS/QCD

We discuss baryon structure in a soft-wall anti-de Sitter/quantum chromodynamics model. From unified point of view we describe nucleon form factors and the electroproduction of the N(1440) Roper resonance. The Roper resonance is identified as the first radially excited state of the nucleon. The obtained results for helicity amplitudes of the Roper electroproduction are in good agreement with the recent results of the CLAS Collaboration at JLab.     

Proton sea quark flavour asymmetry and Roper resonance

We study the proton and the Roper resonance together with the meson cloud model, by constructing a Hamiltonian matrix and solving the eigenvalue equation. The proton sea quark flavour asymmetry and some properties of the Roper resonance are thus reproduced in one scheme.     

Vacuum effects of non-nucleonic baryons in nuclear matter

The role of vacuum properties of non-nucleonic baryons in hadronic field theories is discussed. We use an extension of Walecka's σω model treated at the mean-field level. Due to energy considerations the non-nucleonic baryons yield only vacuum effects near normal nuclear matter density. We study the effect of Roper resonance vacuum fluctuations on the nuclear matter equation of state and Coulomb sum. In addition we perform a schematic calculation of the effect of Δ-isobar vacuum fluctuations on the nuclear matter equation of state. Although the Roper resonance produces only a marginal change in the Coulomb sum, the Roper and delta may produce a significant softening of the equation of state. Thus these normally neglected degrees of freedom might serve an important role.     

A prescription for removing centre-of-mass effects from the bag model

We assume that the state of the MIT bag model describes a hadron which itself is confined to a spherical region of certain size. By demanding that the low energy levels of the quark system and that of the confined hadron coincide we determine selfconsistently all relevant parameters and calculate the Roper resonance mass.     

Nucleon Spin Structure Functions in the Resonance Region and the Duality

We discuss the nucleon spin structure function gl and the difference between the proton and neutrontargets gp1 - gn1 , based on quark model calculation. Quark-hadron duality for the nucleon spin structure function is alsoanalyzed. Effects of the △(1232) and Roper P11(1440) resonances on the spin structure function and on the differencegn1 - gn1 are mentioned. The results of different models for the Roper resonance are also addressed.     

Low-Lying Baryons in Hybrid Quark Model

We study the strong decay processes of the Roper resonance, N*(1440) in the picture of hybrid baryon in which the Roper resonance N*(1440) is interpreted as a state of three quarks and one transverse-electric gluon, q ³ G. A nonrelativistic quark–gluon model is employed, where the dynamics of antiquark–quark–gluon is described in the effective \({^{3}S_{1}}\) vertex in which a quark–antiquark pair is created (destroyed) from (into) a gluon. The wave function of the Roper resonance is properly constructed to take into account the gluon freedom in the nonrelativistic regime. The evaluated strong decay width ratios of N*(1440) are in good agreement with the experimental data.     

Chiral structure of the Roper resonance using complex-mass scheme

The pole mass and the width of the Roper resonance are calculated as functions of the pion mass in the framework of low-energy effective field theory of the strong interactions. We implement a systematic power-counting procedure by applying the complex-mass scheme.     

Baryon resonance analysis from SAID

We discuss the analysis of data from πN elastic scattering and single pion photo- and electropro-duction. The main focus is a study of low-lying non-strange baryon resonances. Here we concentrate on some difficulties associated with resonance identification, in particular the Roper and higher P_(11) states.     

J/Ψ衰变的Roper共振态结构的研究

通过J/Ψ→p, p*, N**衰变,研究了Roper共振态的混杂态结构对衰变角分布和分支比的影响. 计算结果表明,如果Roper共振态为纯混杂态,那么J/Ψ→p*, N**的角分布几乎相等, 而J/Ψ衰变到混杂态的衰变宽度还不到J/Ψ→p 的1%, 给出了Γ(J/Ψ→ N* )/Γ(J/Ψ→p)和Γ(J/Ψ→ N**)/Γ(J/Ψ→ p)随混合参数的变化关系, 并讨论了在J/Ψ衰变中研究Roper混杂态结构的可能性.The structure of Roper resonance is studied as hybrid states through decays J/Ψ→p*, N** by calculating the angular distributions and decay widths. The results show that the angular distribution parameters for decays J/Ψ→p*, N** are almost equal if the Roper is identified as a pure hybrid state, while their decay width are less the 1% of that for the decay J/Ψ→p, and the variance of the ratio Γ(J/Ψ→N*p)/Γ(J/Ψ→p) and Γ(J/Ψ→N**)/ Γ(J/Ψ→p) with the mixing parameter are presented,and also the scheme to identify the Roper structure in J/Ψ decays is discussed.     

Lattice results on nucleon/roper properties

In this proceeding, I review the attempts to calculate the Nucleon resonance (including Roper as first radially excited state of nucleon and other excited states) using lattice quantum chromodynamics (QCD). The latest preliminary results from Hadron Spectrum Collaboration (HSC) with m_n≈380 MeV are reported. The Sachs electric form factor of the proton and neutron and their transition with the Roper at large Q~2 are also updated in this work.     

πN SCATTERING PHASE SHIFTS IN A MODIFIED SKYRME MODEL

The P-wave phase shift of πN scattering and the mass and width of the Roper resonance are computed in a modified Skyrme model.The results are better than those calculated from the original Skyrme model.     

Q2-Dependence of the Bjorken Sum Rule in the Resonance Region

Q²-evolution of the Bjorken sum rule in the resonance region is studied. The roles of the Roper resonance N^* (1440) estimated by the constituent quark model and by the hybrid model are stressed. Moreover, the Q²- dependence of the Gerasimov-Drell-Hearn sum rule contributed by the resonances is also discussed.     

核子共振态的螺旋度振幅的计算

相对论夸克模型用来计算面和N^*的电产生振幅.介子云的贡献是一个重要的课题.计算表明考虑了介子云的作用对Δ和N^*(1440)螺旋度振幅的解释将会有明显的改进.这有助于进一步认识Roper共振态的性质.     

Excitation of the Roper resonance in single- and double-pion production in nucleon-nucleon collisions⋆

In most investigations the Roper resonance is sensed only very indirectly via complex partial-wave analyses. We find indications for its excitation in the invariant nπ⁺ mass spectrum of the pp → npπ⁺ reaction at M ≈ 1360 MeV with a width of ≈ 150 MeV . The values fit very favorably to the most recent phase shift results as well as to the observations at BES. In the near-threshold two-pion production pp → ppπ⁰π⁰ , where the Roper excitation and its subsequent decays via the routes N ^* → Δπ → Nππ and N ^* → Nσ are the only dominant processes, we find its direct decay into the Nσ channel to be the by far dominating decay process --in favor of a monopole excitation of the Roper resonance.     

Effects of bag surface motion with relativistic kinematics

Radial surface motion of the baryon bag is carried out in a model with relativistic kinematics, with confinement the result of volume energy and surface tension and the pion field coupled to the bag surface. We calculate radial wave functions for the nucleon, the Δ(1233) and the Roper resonance N^*(1450), which is identified as the first radial excitation of the nucleon.

Results are used to calculate form factors and pionic decay widths of the baryons examined. The approximations made in these calculations are discussed in extensio.     

Series solution of hydromagnetic flow and heat transfer with Hall effect in a second grade fluid over a stretching sheet

We examine the problem of flow and heat transfer in a second grade fluid over a stretching sheet [K. Vajravelu, T. Roper, Int. J. Nonlinear Mech. 34, 1031 (1999)]. The equations considered by Vajravelu and Roper [K. Vajravelu, T. Roper, Int. J. Nonlinear Mech. 34, 1031 (1999)], are found to be incorrect in the literature. In this paper, we not only corrected the equation but found a useful analytic solution to this important problem. We also extended the problem for hydromagnetic flow and heat transfer with Hall effect. The explicit analytic homotopy solution for the velocity field and heat transfer are presented. Graphs for the velocity field, skin friction coefficient, and rate of heat transfer are presented. Tables for the skin friction coefficient and rate of heat transfer are also presented. The convergence of the solution is also properly checked and discussed.