Wan Shao-Long

Analysis of X(1576) as a Tetraquark State with the QCD Sum Rules

In this letter, we take the point of view that the X(1576) be tetraquark state which consists of a scalar-diquark and an anti-scalar-diquark in relative

Polaron in Bose–Einstein–Condensation System

P

Calculation of Kaon Electromagnetic Form Factor in the Framework of Coupled Schwinger—Dyson and Bethe—Salpeter Formulation

-wave, and calculate its mass in the framework of the QCD sum rules approach. The numerical value of the mass

An extensive calculation of the properties of a one-dimensional polaron

m_X=(1.66\pm 0.14) GeV

Ground State Mass Spectrum for Scalar Diquarks with Bethe–Salpeter Equation

is consistent with the experimental data, there may be some tetraquark component in the vector meson X(1576).We take the viewpoint that X(1576) is the tetraquark state which consists of a scalar diquark and an anti-scalar-diquark in relative P-wave, and calculate its mass in the framework of the QCD sum rule approach. The numerical value of the mass mX = (1.66±0.14) GeV is consistent with the experimental data. There might be some tetraquark components in the vector meson X(1576).

Calculation of the π Meson Electromagnetic Form Factor

We consider the motion of an impurity in a Bose–Einstein condensate system at T = 0 K with the contact interactions for boson-boson and boson-impurity. Under the forward-scattering approximation, we obtain a Frohlich-like Hamiltonian for this system, which means that a polaron can be formed. The effective mass, the phonon number and the energy to form a polaron are obtained. We also discuss the validity of the forward-scattering approximation for this system.

Calculation of kaon electromagnetic form factor

The kaon electromagnetic form factor is calculated in the framework of coupled Schwinger–Dyson equation in rainbow approximation and Bethe–Salpeter equation in ladder approximation with the modified flat-bottom potential, which is the combination of the flat-bottom potential with considerations for the infrared and ultraviolet asymptotic behaviours of the effective quark-gluon coupling. All our numerical results give good fit to experimental values and other theoretical results.

A new variational calculation for N-dimensional polarons in the strong-coupling limit.

A refined approach where the wave function is gradually improved is developed in the one-dimensional (1D) large-Frohlich-polaron problem. The results for the ground-state energy, the effective mass, and the average number of virtual phonons are obtained for a wide range of the coupling constant It, and are in agreement with those of the Feynman path-integral formalism. In addition, in the weak-coupling limit, the expansions of these observables in powers of the coupling constant are exactly calculated up to the alpha 3-term. They are E=- alpha -0.06066 alpha 2-0.00844 alpha 3, m*=1+0.5 alpha +0.19194 alpha 2+0.06912 alpha 3, and N=0.5 alpha +0.12132 alpha 2+0.029540 alpha 3, which agree with the known results of the fourth-order perturbation theory.

Calculations on some properties of the pion in the framework of Schwinger - Dyson and Bethe - Salpeter equations

In this article, we study the structures of the pseudoscalar mesons π, K and the scalar diquarks Ua, Da, Sa in the framework of the coupled rainbow Schwinger–Dyson equation and ladder Bethe–Salpeter equation with the confining effective potential. The u, d, s quarks have small current masses, and the renormalization is very large, the mass poles in the timelike region are absent which implements confinement naturally. The Bethe–Salpeter wavefunctions of the pseudoscalar mesons π, K, and the scalar diquarks Ua, Da, Sa have the same type (Gaussian type) momentum dependence, center around zero momentum and extend to the energy scale about q2 = 1 GeV2, which happens to be the energy scale for the chiral symmetry breaking, the strong interactions in the infrared region result in bound (or quasi-bound) states. The numerical results for the masses and decay constants of the π and K mesons can reproduce the experimental values, and the ground state masses of the scalar diquarks Ua, Da, Sa are consistent with the existing theoretical calculations. We suggest a new Lagrangian which may explain the uncertainty of the masses of the scalar diquarks.

Calculations of the Decay Constant and Radius of the Pion

The modified flat-bottom potential (MFBP) is given by the combination of the flat-bottom potential with considerations for the infrared and ultraviolet asymptotic behaviour of the effective quark-gluon coupling. The π meson electromagnetic form factor is calculated in the framework of the coupled Schwinger-Dyson equation and the Bethe-Salpeter equation in the simplified impulse approximation (dressed vertex) with the MFBP. All our numerical results give a good fit to experimental values.