Searcharxiv⌕ Search

arXiv subjects

Wei-Min Zhang

Publications and source records attributed to Wei-Min Zhang.

106 records · Page 6Linked to original sources
arXiv1998

A Covariant Light-Front Model of Heavy Mesons within HQET

In this paper we construct a covariant light-front model of heavy mesons within the framework of heavy quark effective theory (HQET). The covariant model consists of the light-front heavy meson bound states constructed in the heavy quark limit with heavy quark symmetry and heavy quark effective theory as its basis. Within this model, the Isgur-Wise function and decay constants in the infinite quark mass limit can be evaluated in a very simple and the most general way. The results are ensured to be consistent with heavy quark symmetry. From the heavy-quark-limit bound states, we can further develop a systematic approach to calculate $1/m_Q$ corrections from the $1/m_Q$ expansion of QCD. This covariant model can serve as a quasi-first-principles description of heavy meson dynamics, namely, a phenomenological covariant bound state in the heavy quark limit which is consistent with heavy quark symmetry, plus a reliable first-principles computation of the $1/m_Q$ corrections in HQET in terms of the $1/m_Q$ expansion of the fundamental QCD theory.

hep-ph↗
arXiv1997

Field-Theoretic Realization of Heavy Meson as Composite Particle

We construct a realistic field-theoretic model for the structure of a heavy meson in the heavy quark limit. The model is fully covariant and satisfies heavy quark symmetry. The Isgur-Wise function, the decay constant, and the axial vector coupling constant are studied. This model overcomes the limitations caused by non-covariance of the light-front quark model, and provides an ideal framework to systematically evaluate the heavy quark symmetry breaking effects caused by the $1/m_Q$ correction terms in the heavy quark effective theory of quantum chromodynamics.

hep-ph↗
arXiv1997

Influence of Dynamical Pauli Effect and Dynamical Symmetry Breaking to Quantum Chaos

In this paper, we study the influence of quantum effects to chaotic dynamics, especially the influence of Pauli effect and dynamical symmetry breaking to chaotic motions. We apply the semiquantal theory to the Sp(6) fermion symmetry model in nuclear collective motion. We demonstrate that quantum chaos appears when dynamical symmetry is broken. We further show that dynamical Pauli effect enhances quantum chaos.

chao-dyn↗
arXiv1997

Radiative Leptonic B Decays in the Light Front Model

Within the light front framework, we calculate the form factors for $B\toγ$ transitions directly in the entire physical range of momentum transfer. Using these form factors, we study the radiative decays of $B\to lν_lγ$ and $B_{s(d)}\toν\barνγ$. We show that the decay rates of $B\to lν_lγ(l=e,μ)$ and $B\toν\barνγ$ are larger than that of the corresponding purely leptonic modes. Explicitly, in the standard model, we find that the branching ratios of $B\to μν_μγ$ and $B_s\toν\barνγ$ are $3.7\times 10^{-6}$ and $5.0\times 10^{-8}$, in contrast with $3\times 10^{-7}$ and 0 for $B\toμν_μ$ and $B\toν\barν$, respectively.

hep-ph↗
arXiv1997

Examination of Wandzura-Wilczek Relation for $g_2(x,Q^2)$ in pQCD

In order to examine the validity of Wandzura-Wilczek relation for the polarized DIS structure function $g_2(x,Q^2)$, we use the light-front time-ordering pQCD to calculate $g_2(x,Q^2)$ at order $α_s$ on a quark target. We find that the study of the transverse polarized structure function in pQCD is only meaningful if we begin with massive quarks. The result shows that the Wandzura-Wilczek relation for $g_2(x,Q^2)$ is strongly violated by the quark mass in pQCD.

hep-ph↗
arXiv1997

Light-Front QCD and Heavy Quark Systems

In this series of lectures, I shall begin with the current investigations on phenomenology of hadron dynamics to demonstrate the importance of solving hadronic bound states within the framework of light-front (LF) QCD. Then, I will describe the basic procedure how to formulate the canonical theory of LFQCD, including light-front quantization of QCD, light-front gauge singularity, and light-front two-component formalism. I will also present a complete one-loop QCD calculation in terms of the light-front time-ordering perturbation theory, in comparison with the usual covariant perturbative QCD calculation. Following thereby I will discuss the development of heavy-quark effective theory and the manifestation of heavy quark symmetry on the light-front. Finally, by applying recently developed similarity renormalization group approach to light-front heavy quark effective theory, I will show a rigorous derivation of quark confinement interaction from LFQCD and its application to solve heavy hadron bound states.

hep-ph↗
arXiv1997

A Weak-Coupling Treatment of Nonperturbative QCD Dynamics to Heavy Hadrons

Based on the recently developed light-front similarity renormalization group approach and the light-front heavy quark effective theory, we derive analytically from first-principles QCD a heavy quark light-front Hamiltonian which contains explicitly a confinement interaction at long distances and a Coulomb-type interaction at short distances. With this light-front QCD Hamiltonian, we further demonstrate that the nonperturbative QCD dynamics of the strongly interacting heavy hadron bound states can be treated as a weak-coupling problem.

hep-ph↗
arXiv1996

On the Matrix Element of the Transverse Component of Bilocal Vector Current and its Parton Interpretation

In this paper we study the matrix element of the transverse component of the bilocal vector current in the context of deep inelastic scattering. BJL limit of high energy amplitudes together with light-front current algebra imply the same parton interpretation for its matrix element as that of the plus component. On the other hand, the transverse component depends explicitly on the gluon field operator in QCD, appears as "twist three" and hence its matrix element has no manifest parton interpretation. In this paper we perform calculations in light-front time-ordering perturbative QCD for a dressed quark target to order $α_s$ and demonstrate that the matrix element of the transverse component of the bilocal vector current has the same parton interpretation as that of the plus component.

hep-ph↗
arXiv1995

Quark Confinement in Light-Front QCD and A Weak-Coupling Treatment to Heavy hadrons

In this paper, we develop a weak-coupling treatment of nonperturbative QCD to heavy hadrons on the light-front. First, we present a derivation of quark confining interaction in light-front QCD for heavy quark systems, based on the recently developed light-front similarity renormalization group approach and the light-front heavy quark effective theory. The resulting effective light-front QCD Hamiltonian $H_λ$ at a low-energy cutoff $λ$ manifests the coexistence of a confining potential and a Coulomb potential. A clear light-front picture of quark confinement emerges. Using this low energy QCD Hamiltonian $H_λ$, we study heavy hadron bound state equations in the framework of a recently proposed possible weak-coupling treatment of non-perturbative QCD. Light-front heavy hadron bound states with definite spin and parity are constructed and the general structure of the corresponding wavefunctions is explored. A Gaussian-type wavefunction ansatz is used to solve the light-front quarkonium bound state equation. We find that the effective coupling constant determined from the quarkonium bound state equation can be arbitrarily small so that the weak-coupling treatment to heavy hadron bound states in light-front QCD is explicitly achieved. Finally, the scale dependence of the effective coupling constant is analytically calculated and the similarity renormalization group $β$ function is determined, from which the running coupling constant in small momentum transfer is given qualitatively by $\overlineα(Q^2) \sim {Λ_{QCD}^2 \over Q^2}$. Such a running coupling constant is the basic assumption in the successful Richardson $Q\overline{Q}$ potential that ensures the existence of a linear confining potential at large distance, but now can be obtained from light-front QCD.

hep-ph↗
arXiv1995

Light-Front Heavy Quark Effective Theory and Heavy Meson Bound States

The heavy quark effective theory is developed on the light-front. Based on this effective theory, a light-front heavy meson bound state with definite spin and parity is constructed. Within the effective theory, the Isgur-Wise function is derived in terms of the asymptotic light-front bound state amplitudes in the limit $m_Q\rightarrow\infty$; the result is a general expression for arbitrary recoil velocities. With the asymptotic form of the BSW amplitudes, the Isgur-Wise function is given by $ξ(v\cdot v')=1/v\cdot v'$. The slope at the zero-recoil point is $ρ^2=-ξ'(1)=1$, in excellent agreement with the recent CLEO result of $ρ^2=1.01\pm0.15\pm0.09$.

hep-ph↗
arXiv1994

Heavy Quark Effective Theory on the Light Front

The light-front heavy quark effective theory is derived to all orders in $1/m_Q$. In the limit $m_Q\rightarrow \infty$, the theory exhibits the familiar heavy quark spin-flavor symmetry. This new formalism permits a straightforward canonical quantization to all orders in $1/m_Q$; moreover, higher order terms have rather simple operator structures. The light-front heavy quark effective theory can serve as an useful framework for the study of non-perturbative QCD dynamics of heavy hadron bound states.

hep-ph↗
arXiv1994

Light-Front Dynamics and Light-Front QCD

In this article we review the basic formulation of light-front field theory and light-front phenomena in strong interaction. We also explore various approaches to the understanding of these phenomena and the associated problems of hadronic bound states based on QCD (quantum chromodynamics) on the light-front.

hep-ph↗
arXiv1993

Is Schrödinger's Conjecture for the Hydrogen Atom Coherent States Attainable

We construct the most general SO(4,2) hydrogen atom coherent states which are the counterpart of Schrödinger's harmonic oscillator coherent states. We show that these states cannot be localized and cannot follow the classical orbits. Thus, Schrödinger's conjecture for the hydrogen atom coherent states is unattainable.

nucl-th↗
arXiv1993

Residual Gauge Fixing in Light-Front QCD

Understanding the nontrivial features of light-front QCD is a central goal in current investigations of nonperturbative light-front field theory. We find that, with the choice of light-front gauge with antisymmetric boundary conditions for the field variables, the residual gauge freedom is fixed and the light-front QCD vacuum is trivial. The nontrivial structure in light-front QCD is determined by non-vanishing asymptotic physical (transverse) gauge fields at longitudinal infinity, which are responsible for nonzero topological winding number.

hep-th↗
arXiv1993

Light-Front QCD: Role of Longitudinal Boundary Integrals

In the canonical light-front QCD, the elimination of unphysical gauge degrees of freedom leads to a set of boundary integrals which are associated with the light-front infrared singularity. We find that a consistent treatment of the boundary integrals leads to the cancellation of the light-front linear infrared divergences. For physical states, the requirement of finite energy density in the light-front gauge $(A_a^+=0)$ results in equations which determine the asymptotic behavior of the transverse (physical) gauge degrees of freedom at longitudinal infinity. These asymptotic fields are generated by the boundary integrals and they are responsible for the topological winding number. They also involve non-local behavior in the transverse direction that leads to non-local forces.

hep-th↗