arXiv subjects
Publications and source records attributed to Chueng-Ryong Ji.
We investigate the form factors and decay rates of exclusive $0^{-}\to0^{-}$ semileptonic meson decays using the constituent quark model based on the light-front quantization. Our model is constrained by the variational principle for the linear plus Coulomb interaction motivated by QCD. Our numerical results are in a good agreement with the available experimental data.
We present the analysis of exclusive $0^{-}$$\to$$0^{-}$ semileptonic heavy meson decays using the constituent quark model based on the light-front quantization. Our model is constrained by the variational principle for the well-known linear plus Coulomb interaction motivated by QCD. Our method of analytic continuation to obtain the weak form factors avoids the difficulty associated with the contribution from the nonvalence quark-antiquark pair creation. Our numerical results for the heavy-to-heavy and heavy-to-light meson decays are in a good agreement with the available experimental data and the lattice QCD results. In addition, our model predicts the two unmeasured mass spectra of $^{1}S_{0}(b\bar{b})$ and $^{3}S_{1}(b\bar{s})$ systems as $M_{b\bar{b}}$=9657 MeV and $M_{b\bar{s}}$= 5424 MeV.
We present a relativistic constituent quark model to analyze the mass spectrum and hadronic properties of radially excited u and d quark sector mesons. Using a simple Gaussian function as a trial wave function for the variational principle of a QCD motivated Hamiltonian, we obtain the mass spectrum consistent with the experimental data. To do the same for several observables such as decay constants and form factors, it seems necessary to include both Dirac and Pauli form factors on the level of constituent quarks. Taking into account the quark form factors, we thus present the generalized formulas for the rho meson decay constant and form factors as well as the $πγ$ transition form factor. We also predict several hadronic properties for the radially excited states.
We have developed a quantum field theoretic framework for scalar and pseudoscalar meson mixing and oscillations in time. The unitary inequivalence of the Fock space of base (unmixed) eigenstates and the physical mixed eigenstates is proven and shown to lead to a rich condensate structure. This is exploited to develop formulas for two flavor boson oscillations in systems of arbitrary boson occupation number. The mixing and oscillation can be understood in terms of vacuum condensate which interacts with the bare particles to induce non-trivial effects. We apply these formulas to analyze the mixing of $η$ with $η'$ and comment on the $K_L K_S$ system. In addition, we consider the mixing of boson coherent states, which may have future applications in the construction of meson lasers.
We present a coupled channel partial wave analysis of nondiffractive S-wave pi+ pi- and K+ K- photoproduction focusing on the KK threshold. Final state interactions are included. We calculate total cross sections, angular and effective mass distributions in both pion-pion and kaon-antikaon channels. Our results indicate that these processes are experimentally measurable and valuable information on the f0(980) resonance structure can be obtained.
Both the mass spectra and the wave functions of the light pseudoscalar ($π,K,η,η'$) and vector($ρ,K^{*},ω,ϕ$) mesons are analyzed within the framework of the light-cone constituent quark model. A gaussian radial wave function is used as a trial function of the variational principle for a QCD motivated Hamiltonian which includes not only the Coulomb plus confining potential but also the hyperfine interaction to obtain the correct $ρ-π$ splitting. For the confining potential, we use (1) harmonic oscillator potential and (2) linear potential and compare the numerical results for these two cases. The mixing angles of $ω-ϕ$ and $η-η'$ are predicted and various physical observables such as decay constants, charge radii, and radiative decay rates $etc.$ are calculated. Our numerical results in two cases (1) and (2) are overall not much different from each other and have a good agreement with the available experimental data. use (1) harmonic oscillator potential and (2) linear potential and compare the numerical results for these two cases. The mixing angles of $ω-ϕ$ and $η-η'$ are predicted and various physical observables such as decay constants, charge radii, and radiative decay rates $etc.$ are calculated. Our numerical results in two cases (1) and (2) are overall not much different from each other and have a good agreement with the available experimental data.
We investigate the form factors and decay rates for the semileptonic decays of the kaon($K_{l3})$ using the light-front quark model. The form factors $f_{\pm}(q^{2})$ are calculated in $q^{+}=0$ frame and analytically continued to the time-like region, $q^{2}>0$. Our numerical results for the physical observables, $f_{-}/f_{+}|_{q^{2}=m^{2}_{l}}=-0.38$, $λ_{+}=0.025$(the slope of $f_{+}$ at $q^{2}=m^{2}_{l}$), $Γ(K^{0}_{e3})=(7.30\pm 0.12)\times10^{6}s^{-1}$, and $Γ(K^{0}_{\mu3})=(4.57\pm0.07)\times10^{6}s^{-1}$ are quite comparable with the experimental data and other theoretical model calculations. The non-valence contributions from $q^{+}\neq 0$ frame are also estimated.
We find that the zero mode($q^{+}=0$ mode of a continuum theory) contribution is crucial to obtain the correct values of the light-front current $J^{-}$ in the Drell-Yan($q^{+}=0$) frame. In the exactly solvable model of (1+1)-dimensional scalar field theory interacting with gauge fields, we quantify the zero mode contribution and observe that the zero mode effects are very large for the light meson form factors even though they are substantially reduced for the heavy meson cases.
We present a rotation average of the two-body scattering amplitude in the lightcone time($τ$)-ordered perturbation theory. Using a rotation average procedure, we show that the contribution of individual time-ordered diagram can be quantified in a Lorentz invariant way. The number of time-ordered diagrams can also be reduced by half if the masses of two bodies are same. In the numerical example of $ϕ^{3}$ theory, we find that the higher Fock-state contribution is quite small in the lightcone quantization.
We examine the role of O(α_s) perturbative corrections to the pion elastic form factor F_π(Q^2). We express the quark current three-point function in terms of light cone variables and use Borel transformation to simultaneously model the Feynman mechanism contribution determined by the soft part of the pion light cone wave function and the hard term involving one gluon exchange. We find that for Q^2 \sim 5 GeV^2 the total one gluon exchange contribution may reach 40% of the soft contribution, even though its hard, factorization scale dependent part remains relatively small.
A comprehensive, relativistic many-body approach to hadron structure is advanced based on the Coulomb gauge QCD Hamiltonian. Our method incorporates standard many-body techniques which render the approximations amenable to systematic improvement. Using BCS variational methods, dynamic chiral symmetry breaking naturally emerges and both quarks and gluons acquire constituent masses. Gluonia are studied both in the valence and in the collective, random phase approximations. Using representative values for the strong coupling constant and string tension, calculated quenched glueball masses are found to be in remarkable agreement with lattice gauge theory.
Motivated by an apparent puzzle of the light-front vacua incompatible with the axial anomaly, we have considered the two-dimensional massless Schwinger model for an arbitrary interpolating angle of the quantization surface. By examining spectral deformation of the Dirac sea under an external electric field semiclassically, we have found that the axial anomaly is quantization angle independent. This indicates an intricate nontrivial vacuum structure present even in the light-front limit.