Extended PCAC Relation and Nucleon Structure

We explore a consistent way to extend the old partially conserved axial vector current (PCAC) relation for a nucleon to a finite q² region. The paper includes an investigation of a chiral Ward-Takahashi identity, the explicit chiral symmetry breaking by a finite current quark mass, the extension of the PCAC relation and the physical consequences. Two explicit relationsbetween the nucleon axial vector form factor g_A(q²), pseudo-scalar form factor g_p(q²) and the pion-nucleon coupling constant g_πNN(q²) are obtained. One of the relations is confirmed, within the experimental error, by observations in the 0 < -q² < 0.2 GeV² region. The other one which. relates g_A(q²) and f_π(q²)g_πNN(q²) is studied by using known empirical facts and dispersion relation. Certain inconsistency, which is in favor of the introduction of a diquark condensation inside a nucleon, is revealed.     

Shot noises of spin and charge currents in a ferromagnet-quantum-dot-ferromagnet system

We have investigated the shot noises of charge and spin current by considering the spin polarized electron tunneling through a ferromagnet-quantum-dot-ferromagnet system. We have derived the spin polarized current noise matrix, from which we can derive general expressions of shot noises associated with charge and spin currents. The spin and charge currents are intimately related to the polarization angles, and they behave quite differently from each other. The shot noise of charge current is symmetric about the gate voltage whose structure is modified by the Zeeman field considerably. There exists oscillations in spin current shot noise in the absence of source-drain bias at zero temperature, and it is asymmetric in the positive and negative regimes of sourcedrain voltage. The shot noise of spin current behaves quite differently from the shot noise of charge current, since the spin current components I_x^s, I_y^s oscillate sinusoidally with the frequency ?_? in the ?th lead, while the I_z^s component of spin current is independent of time.     

Critical Percolation Probabilities for the Next-Nearest-Neighbouring Site Problems on Sierpinski Carpets

In this paper, we compute the next-nearest-neighbouring site percolation (Connections exist not only between nearest-neighbouring sites, but also between next-nearest-neigh bouring sites.) probabilities PC on the two-dimensional Sierpinski carpets, using the translationaldilation method and Monte Carlo technique. We obtain a relation among PC, fractal dimensionality D and connectivity Q. For the family of carpets with central cutouts,(1 - P_c)/(1 - P_c^s) = (D - 1)^1.60, where P_c^s = 0.41, the critical percolation probability for the next-nearest-neighbouring site problem on square lattice. As D reaches 2, P_c = P_c^s = 0.41, which is in agreement with the critical percolation probability on 2-d square lattices with . next-nearest-neigh bouring interactions.     

The Anomaly Coupling of Axigluon and Technicolor Neutral Pseudo Goldstone Bosons

By gauging the anomaly terms according to the gauge group SU(3)_cl x SU(3)_cr × SU(2)_l × U(l)_Y in the technicolor theory, we obtain various possibld anomaly vertices involving technicolor pseudo Goldstone boson and gauge boson (γ, Z, g, g_A). We estimate the decay rates of g_A → gP⁰, g_A → P_A⁰³γ and g_A → P_A⁰³Z.     

Reggeon, Pomeron and Glueball, Odderon-Hadron-Hadron Interaction at High Energies - From Regge Theory to Quantum Chromodynamics

Based on analysis of scattering matrix S, and its properties such as analyticity, unitarity, Lorentz invariance, and crossing symmetry relation, the Regge theory was proposed to describe hadron-hadron scattering at high energies before the advent of QCD, and correspondingly a Reggeon concept was born as a mediator of strongly interaction. This theory serves as a successful approach and has explained a great number of experimental data successfully, which proves that the Regge theory can be regarded as a basic theory of hadron interaction at high energies and its validity in many applications. However, as new experimental data come out, we have some difficulties in explaining the data. The new experimental total cross section violates the predictions of Regge theory, which shows that Regge formalism is limited in its applications to high energy data. To understand new experimental measurements, a new exchange theory was consequently born and its mediator is called Pomeron, which has vacuum quantum numbers. The new theory named as Pomeron exchange theory which reproduces the new experimental data of diffractive processes successfully. There are two exchange mediators： Reggeon and Pomeron. Reggeon exchange theory can only produce data at the relatively lower energy region, while Pomeron exchange theory fits the data only at higher-energy region, separately. In order to explain the data in the whole energy region, we propose a Reggeon-Pomeron model to describe high-energy hadron- hadron scattering and other diffractive processes. Although the Reggeon-Pomeron model is successful in describing high-energy hadron-hadron interaction in the whole energy region, it is a phenomenological model. After the advent of QCD, people try to reveal the mystery of the phenomenological theory from QCD since hadron-hadron processes is a strong interaction, which is believed to be described by QCD. According to this point of view, we study the QCD nature of Reggeon and Pomeron. We claim that the Reggeon exchange is an exchange of mult     

The Singlet Axial Vector Coupling in the Effective Meson Baryon Lagrangian

The Goldberger-Treiman (GT) relation in the singlet channel, being consistent with the EMC experimental results, can be manifested in an extended a model in which the chiral symmetry in the singlet channel is realized in the parity doublet model by assuming that the excited nucleon state S₁₁ N(1535) is the parity partner of the nucleon state. The model gives a natural explanation of the smallness of the singlet axial vector coupling g_A⁰ without the necessity to assume a large strange sea contribution, and is unique in explaining the decay rate of N(1535) → N_η as well.     

Test on Application Range of QCD Sum Rules from Baryon Spectroscopy

By considering the nonperturbative QCD effect via quark and gluon condensates, the confinement terms in effective q-q potential can automatically be given. A potential in the form of (-2α,/3r) + Σ_n^∞ a_2n+1r²ⁿ⁺¹ + (Yukawa-type terms) where positive and negative signs appear alternatively in a_2n+1's is proposed. To testify the validity range of QCD sum rules, the experimental baryon spectrum is fitted and the values of azn+l's as well as their signs are obtained. It is found that in the baryon spectrum calculation, the terms of r³ snd r⁵ are important and higher terms beyond r⁵ can be neglected. Comparing these values with the result calculated from QCD sum rules, some agreements and disagreements are found.     

On the Mixing of K0-K0,D0-D0 and B0-B0

Systematically, we study the long-range contribution to the mixing effects based on the potential model while the QCD correction in Hamiltonian being taken into account. We have found that the long-distance effects are important to K⁰-K⁰ and D⁰-D⁰, but B⁰-B⁰. The QCD correction causes a change to the results, enhances the mixing, for K⁰-K⁰, by a factor of 1.3, whereas for D⁰-D⁰ it is a suppression of about 0.7. The absorptive parts which give rise to ΔΓ have also been discussed and the diquark-intermediate-state contributions to D and B systems are included.     

A Determination of Nucleon Form Factor Ratios Using Perturbative QCD

Using perturbative QCD in conjunction with CVC and standard electroweak theory, it is shown that at large Q², F₁ⁿ/F₁^P = F₂ⁿ/F₁^P = -0.69. The comparison with other results on form factor ratios from QCD sum rules and/or PQCD is carried out.     

Superthermal Electron Produced in Relativistic Laser-Plasma Interaction

The dynamics of a relativistic electron submitted to an intense, plane wave, linearly polarized laser field is reviewed. Based on the dynamics, the temperature of the electron in the laser field is defined and calculated. It is found that the calculated temperature fits the first temperature observed in the experiment by Malka et al. A model to evaluate the electron temperature by taking the electron-ion scattering into account is proposed. It is found that when I≥4.0×10¹⁸ W/cm² the electron temperature by considering the scattering, T_h^s, is evidently larger than the electron temperature without considering the scattering, T_h. This result is in favor of explaining the two-temperature distribution of the electron energy observed in the experiment by Malka et al.     

Gluonic Origin and Glueball Nature of Pomeron

The Pomeron-nucleon coupling vertex is theoretically derived from the fundamental theory of strong interaction QCD. The empirical vertex βγ^μF1 （t） used commonly in diffractive processes with a coupling strength β = 6.0 GeV^-1 is initially obtained from QCD theoretically. Our study not only reproduces the Pomeron-nucleon coupling from QCD but also clearly shows the gluonlc origin and glueball nature of Pomeron, which is a longstanding puzzle. From this investigation, we claim that Pomeron can be regarded as a Reggeized tensor glueball ζ（2230） with quantum numbers of I^GJ^PC = 0＋2＋＋. Since the tensor glueball ζ（2230） lies on the Pomeron trajectory αp（t = Mζ^2） = 2, the longstanding puzzle that no physical particle lies on the Pomeron trajectory, αp（t） = 1.08 ＋ 0.20 GeV^-2 .t, seems to be solved.     

W-T Identities,Normalization of the BS Wave Function and Properties of the Pion

We discuss some problems concerned with the normalization of the BS wave function in connection with Ward-Thkahashi identities in the Lorentz covariant Bethe-Salpeter formalism proposed in the previous work. Physical quantities of the pion as a Goldstone boson, including the π⁰ → 2γ amplitude are calculated in the QCD motivated models and results are in agreement with the experimental data.     

强子物质中的介子-介子散射(英文)

建立了一个夸克交换模型和提出了一个夸克-反夸克湮灭模型来研究介子-介子散射。从量子色动力学我们得到一个依赖于温度的夸克作用势。从微扰量子色动力学推导对应于夸克-反夸克湮灭和产生的跃迁势。模型给出基态介子质量的实验值,并且在玻恩近似下能说明真空中阈能附近的π-π弹性散射相移的实验值。从S矩阵元出发,推导散射的跃迁振幅和截面公式。计算出涉及π,ρ,K,K*的反应的非极化截面。发现这些截面具有强烈的温度依赖性。We have established a quark-interchange model and have proposed a quark-antiquark annihilation model to study meson-meson scattering. From QCD we obtain a temperature-dependent quark potential. The transition potential corresponding to quark-antiquark annihilation and creation is derived in perturbative QCD. The experimental ground-state meson masses are reproduced and the experimental data of elastic phase shifts for ππ scattering near the threshold energy in vacuum can be accounted for in the Born approximation. Starting from S-matrix element, we derive the transition amplitude and the cross section for the scattering. Unpolarised cross sections for reactions involving π, ρ, K and K* are calculated. Remarkable temperature dependence of the cross sections is found.     

Approach to Perturbative QCD Results in Transition Amplitudes of Nucleon Negative-Parity Resonances

The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance S₁₁(1535). Our analysis indicates that the constraints of the transition amplitude for the S₁₁ resonance at the limit Q²→∞ by QCD sum rule calculations are not applicable at a moderate Q² range of 2.5 ～ 4 GeV² compared with the present available data if the contribution of S₁₁ is dominant in the Q² limit.     

Studies of Bs^0 → η＇η＇ Decays in pQCD Approach

We calculate the CP averaged branching ratios and CP-violating asymmetries for Bs^0 → η＇η＇ and η＇η＇ decays in the perturbative QCD （pQCD） approach here. The pQCD predictions for the C P-averaged branching ratios are Br（Bs^0 → ηη）=（14.2-7.5^＋18.0） ×10^-6,Br（Bs^0 → ηη＇）=（12.4-7.0^＋18.2）×10^-6,and Br（Bs^0 → η＇η＇） =（9.2-4.9^＋15.3）×10^-6, which agree well with those obtained by employing the QCD factorization approach and also be consistent with available experimental upper limits. The gluonic contributions are small in size： less than 7% for Bs →ηηand ηη＇ decays, and around 18% for Bs →η＇η＇ decay. The CP-violating asymmetries for three decays are very small： less than 3% in magnitude.     

Analysis of X(5568) as Scalar Tetraquark State in Diquark-Antidiquark Model with QCD Sum Rules

In this article, we take the X(5568) as the diquark-antidiquark type tetraquark state with the spin-parity J^P=0⁺, construct the scalar-diquark-scalar-antidiquark type current, carry out the operator product expansion up to the vacuum condensates of dimension-10, and study the mass and pole residue in details with the QCD sum rules. We obtain the value M_X=(5.57±0.12) GeV, which is consistent with the experimental data. The present prediction favors assigning the X(5568) to be the scalar tetraquark state.     

A method for computing higher gluonic power corrections to QCD charmonium sum rules

We propose a new method of calculating gluonic power corrections in QCD based on the Schwinger gauge x_μA^μ(x) = 0. Results of the calculation of the O(m_c⁻⁶)-correction to the QCD charmonium sum rules are presented and discussed.     

Nonperturbative nonrenormalization theorem for supersymmetric QCD

We show that no radiative masses are acquired by the Goldstone pion supermultiplet in supersymmetric QCD. Thus, in contrast to ordinary QCD, the mass difference m_π²+−m_π²0 remains zero even after electromagnetism is turned on. Bound state Goldstone supermultiplets obey a nonrenormalization theorem analogous to that obeyed by elementary chiral superfields.     

Coupling Vertex of the Pomeron to Nucleon in QCD

The coupling vertex of the Pomeron to nucleon is derived from QCD. A γμ coupling vertex and coupling strength of β＝ 6.0 GeV-1, which has been used commonly as a free parameter in literature, are obtained. The result leads a support to the belief that the Pomeron could be a tensor glueball ξ(2230) with quantum numbers of IGJPC ＝ 0+2++ in nature.