Nucleon Spin Content in a Relativistic Quark Potential Model Approach

Based on a relativistic quark model approach with an effective potential , the spin content of the nucleon is investigated. Pseudo-scalar interaction between quarks and Goldstone bosons is employed to calculate the couplings between the Goldstone bosons and the nucleon. Different approaches to deal with the center of mass correction in the relativistic quark potential model approach are discussed.

Electric and Magnetic Form Factors of Proton in Relativistic Constituent QuarkModel

Based on relativistic constituent quark (RCQ) model, the electric and magnetic form factors are analyzed. The ratio of the two form factors for the proton , which is an image of its charge and magnetization distributions, is calculated in the light-front formulism of RCQ model. Recently, this ratio was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the polarization technique. The new data presented span the range and are well described by a linear Q2 fit. Also, the ratio reaches a constant value while Q2 becomes larger than 2 (GeV)2. Our calculation results are presented and appear to be consistent with the experimental ones.

Weak decays ofΞ^((′))_(c)→Ξin the light-front quark model

Without contamination from the final state interactions,the calculation of the branching ratios of semileptonic decays Ξ^((′))_(c)→Ξ+e^(+)ν_(e) may provide further information about the inner structure of charmed baryons.Moreover,by studying such processes,one can better determine the form factors of Ξ_(c)→Ξ that can be further applied to relevant estimates.In this study,we used the light-front quark model to carry out computations where the three-body vertex functions forΞ_(c) and Ξ are employed.To fit the new data of the Belle II,we re-adjusted the model parameters to obtain β_(s[sq])=1.07 GeV,which is 2.9 times larger than β_(ss)=0.366 GeV.This value may imply that the ss pair in Ξ constitutes a more compact subsystem.Furthermore,we investigated the non-leptonic decays of Ξ^((′))_(c)→Ξ,which will be experimentally measured soon.Thus,our model will be tested in terms of consistency with the new data.

Dissociation cross sections ofψ(3770),ψ(4040),ψ(4160),andψ(4415)mesons with nucleons

We study the dissociation of ψ(3770), ψ(4040), ψ(4160), and ψ(4415) mesons in collision with nucleons, which takes place in high-energy proton-nucleus collisions. The quark interchange between a nucleon and a ■ meson leads to the dissociation of the ■ meson. We consider the reactions:■, and■, where R stands for ψ(3770), ψ(4040), ψ(4160), or ψ(4415). A reaction of a neutron and a ■ meson corresponds to a reaction of a proton and the ■ meson by replacing the up quark with the down quark and vice versa. Transition-amplitude formulas are derived from the S-matrix element.Unpolarized cross sections are calculated with the transition amplitudes for scattering in the prior form and in the post form. The cross sections relate to nodes in the radial wave functions of ψ(3770), ψ(4040), ψ(4160), and ψ(4415) mesons.

Decay rates of charmonia within a quark-antiquark confining potential

In this work, we investigate the spectroscopy and decay rates of charmonia within the framework of the non-relativistic SchrSdinger equation by employing an approximate inter quark-antiquark potential. The spin hyperfine, spin-orbit and tensor components of the one gluon exchange interaction are employed to compute the spectroscopy of the excited S states and a few low-lying P and D waves. The resultant wave functions at zero inter- quark separation as well as some finite separations are employed to predict the di-gamma, di-leptonic and di-gluon decay rates of charmonia states using the conventional Van Royen-Weisskopf formula. The di-gamma and di-leptonic decay widths are also computed by incorporating the relativistic corrections of order v4 within the NRQCD formalism. We have observed that the NRQCD predictions with their matrix elements computed at finite radial separation yield results which are found to be in better agreement with experimentM values for both di-gamma and di-leptonic decays. The same scenario is seen in the case when di-gamma and di-leptonic decay widths are computed with the Van Royen- Weisskopf formula. It is also observed that the di-gluon decay width with the inclusion of binding energy effects are in better agreement with the experimental data available for 1S-2S and 1P. The di-gluon decay width of 3S and 2P waves waves are Mso predicted. Thus, the present study of decay rates clearly indicates the importance of binding energy effects.

Systematic analysis of strange single heavy baryons Ξ_(c) and Ξ_(b)

Motivated by the experimental progress in the study of heavy baryons,we investigate the mass spectra of strange single heavy baryons in theλ-mode,using the relativistic quark model and the infinitesimally shifted Gaussian basis function method.We show that experimental results are well captured using the predicted masses.The root mean square radii and radial probability density distributions of the wave functions are analyzed in detail.Meanwhile,the mass spectra allow us to successfully construct the Regge trajectories in the(J,M^(2))plane.We also preliminarily assign quantum numbers to the recently observed baryons,includingΞ_(c)(3055),Ξ_(c)(3080),Ξ_(c)(2930),Ξ_(c)(2923),Ξ_(c)(2939),Ξ_(c)(2965),Ξ_(c)(2970),Ξ_(c)(3123),Ξ_(b)(6100),Ξ_(b)(6227),Ξ_(b)(6327),andΞ_(b)(6333).Finally,the spectral structure of strange single heavy baryons is discussed.Accordingly,we predict several new baryons that may be observed in forthcoming experiments.

D_(s_1)(2536)^+ decays and the structure of P-wave charmed strange mesons

We calculate the D s 1 （2536） ^＋ decays into D＊K channels,including the decay D s 1 （2536） ＋ → D ＋ π-K ＋ through a virtual D＊0 in a constituent quark model.Widths and S/D amplitudes ratio are in agreement with the recent Belle and BABAR data,being the results sensitive to 1 P 1 and 3 P 1 mixture.