Glueball Masses from Hamiltonian Lattice QCD

We calculate the masses of the 0⁺⁺, 0^-- and l^+- glueballs from QCD in 3+1 dimensions using an eigenvalue equation method for Hamiltonian lattice QCD developed and described by S.H. GUO et al. The mass ratios become approximately constants in the coupling region 6/g²∈[6.0,6.4], from which we estimate M(0^--)/M(0⁺⁺) = 2.44 ± 0.05 ± 0.20 and M(l^+-)/M(0⁺⁺) = 1.91 ± 0.05 ± 0.12.     

πN scattering and electromagnetic corrections in the perturbative chiral quark model

We apply the perturbative chiral quark model to give predictions for the electromagnetic O(p²) low-energy couplings of the ChPT effective Lagrangian that define the electromagnetic mass shifts of nucleons and first-order (e²) radiative corrections to the πN scattering amplitude. We estimate the leading isospin-breaking correction to the strong energy shift of the π⁻p atom in the 1s state, which is relevant for the experiment “Pionic Hydrogen” at PSI.     

The Rare DecayK+ →π+vv and Effects of Charged Technipions

In this paper we calculate the contributions to the FCNC rare decay from the charged technipion P^± and P₈^± in the frarnervork of technicolor theory. We find that: (a) P^± can provide a positive but relatively small contribution to the process; (b) the contribution is large and positive for relatively light P₈^± and becomes negative for m_p8 ≥ 531 GeV; (c) the enhancement to the ratio BR() can be as large as a factor of 30 for m_p1 = 50 GeV and m_p8 = 100 GeV; (d) the lower mass bound on m_p8 is m_p8 > 220,190 GeV for m_p1 = 50,200 GeV, respectively     

Three-loop mixing of dipole operators

We calculate the complete three-loop O(alpha(3)(s)) anomalous dimension matrix for the dimension-five dipole operators that arise in the standard model after integrating out the top quark and the heavy electroweak bosons. Our computation completes the three-loop anomalous dimension matrix of operators that govern low-energy |DeltaF| = 1 flavor-changing processes, and represents an important ingredient of the next-to-next-to-leading order QCD analysis of the B--> X(s)gamma decay.     

Long-range SL(2) Baxter equation in N=4 super-Yang–Mills theory

Relying on a few lowest order perturbative calculations of anomalous dimensions of gauge invariant operators built from holomorphic scalar fields and an arbitrary number of covariant derivatives in maximally supersymmetric gauge theory, we propose an all-loop generalization of the Baxter equation which determines their spectrum. The equation does not take into account wrapping effects and is thus asymptotic in character. We develop an asymptotic expansion of the deformed Baxter equation for large values of the conformal spin and derive an integral equation for the cusp anomalous dimension.     

Prompt photon production in ee annihilation

We investigate the production of prompt photons in e⁺e⁻ annihilation events. The result of the dipole cascade model, as implemented in the ARIADNE MC, is compared with the perturbative O(_SQED) matrix element, which is expected to be reliable for relatively hard photons. We show that for softer photons the dipole model agrees with Low's theorem. The model interpolates smoothly between the two limiting situations in good agreement with the experimental data for OPAL. The result can be interpreted in terms of a notion of “time ordering” in the production process, and we show how this can be further investigated experimentally.     

Foundations of electrodynamics: S.R. de Groot and L.G. Suttorp, (North-Holland Publishing Company,Amsterdam, 1972. xii-535 pages. Fl. 140.-)

We show that the anomalous dimension of the fundamental field is connected to the anomalous dimensions of the high spin bilinear operators. The dimensions of these operators can be determined by examining the violations of the Bjorken scaling law in deep-inelastic electron-proton scattering. The structure function at field ω near to one has a power dependence of q², the exponent being the anomalous dimension of the “parton” field.     

Non-1/mb power suppressed contributions to inclusive B → Xsll decays

We compute non-perturbative contributions to B → X_sl⁺l⁻ that are not explicitly suppressed by powers of the b-quark mass. They are proportional to and arise from an interference between the free-quark amplitude and high order terms in the matrix element of the four-quark operator s⁻γ^μ(1 − γ₅)cc^−βγ_μ(1 − γ₅)b_β. This correction is found to be small over most of the dalitz plot except near the charm threshold. Unfortunately, the perturbative computation we have performed is invalid near charm threshold and we do not except to see the structure found at lowest order reproduced in the data. We conclude that these non-perturbative contributions do not significantly modify the previous analysis of B → X_sl⁺l⁻.     

Anomalous dimensional quark counting of hard processes in QCD

An approach to the investigation of hard jet and single-particle production asymptotics in hadron collisions is proposed. In the leading order of QCD perturbation theory, the anomalous dimension quark counting (ADQC) rules are derived, which determine the logarithmic corrections to the point-like power asymptotics in terms of anomalous dimensions of the non-singlet and singlet quark and gluon operators. It is argued, that taking the quark distribution and fragmentation functions up to the two-loop order does not destroy universality of the proposed ADQC rules. A parameter-free solution for the effective power exponents in a wide class of hard processes is obtained.     

The Systematic Approximation and the Systematic Adiabatic Approximation for the Stochastic Systems Driven by O-U Noises

In this paper, we generalize the systematic approximation and the systematic adiabatic approximation developed by G. Schöner and H.aken^[1,2] to the stochastic systems driven by O-U noises. After eliminating the fast variables st, we introduce a new family of stochastic processes K_t^(υ) (υ≥2) in the equations for the order parameters vt. A typical model serves to illustrate how to derive the equation for the order parameter and how to calculate the statistical properties of the new stochastic processes K_t^(υ) (υ≥2). Some significant discussions and conclusions are given in Sec. V.     

Constraints from conformal covariance on the mixing of operators of lowest twist

In massless QCD the operators which diagonalize the anomalous dimension matrix to first order in α_s form representations of the conformal group. This is proved by using anomalous Ward identities. Only a subgroup, the so-called collinear conformal group SU(1, 1) ? SO(2, 1), acts on the restricted class of operators of lowest twist. Towers of local operators bilinear and trilinear in the quark fields are constructed. They are considered as polynomials in the derivatives acting on the basic quark fields: bilinear operators are given by Jacobi polynomials, trilinear operators by Appell's polynomials.By using the explicit form of the anomalous dimension matrix we verify that the constructed bilinear collinear conformal operators are in fact eigenvectors. As the conformal trilinear operator basis is degenerate, the eigenvectors of the mixing matrix of trilinear operators are not determined by conformal covariance alone. However, by taking a conformal basis the number of independent operators is reduced considerably.     

Top-Quark Condensate at Finite Temperature and Electroweak Symmetry Restoration

The gap equation at finite temperature in the top-quark condensate scheme of electroweak symmetry breaking is proven to have the identical form in both the imaginary and real time formalisms of thermal field theory. By means of the gap equation, combined with the basic relation to define the vacuum expectation value v of the effective Higgs field, we analyze the dependence on temperature T and chemical potential p of the dynamical top-quark mass as the order parameter characteristic of symmetry breaking, and obtain the p-T criticality curve for symmetry restoration. We find out that the critical temperature T_c = 2υ for μ = 0 and the critical chemical potential μ_c = 2 π υ / √3 for T = 0. When μ = 0, the top-quark mass near T_c has the leading (T_c² - T²)^1/2 behavior with an extra factor dependent on temperature T and the momentum cutoff Λ. However, it is generally argued that the symmetry restoration at T ≥ T_c is still a second-order phase transition.     

Radiative Decay Bc→ Ds*γ in the Technicolor with a Massless Scalar Doublet Model

Applying perturbative QCD, we study the process B_c→D_s^*γ in the technicolor with a massless scalar doublet model (TCMLSM). There are mainly two mechanisms contributing to the B_c→ D_s^*γ process. One proceeds through the short distance b→sγ transition and the other through weak annihilation accompanied by a photon emission. We find that, compared with the standard model, the modification of B_c→ D_s^*γ from π_p (the physical pions in the TCMLSM) is so small that can be neglected for the allowed mass of π_p. The weak-annihilation contribution is found to be about one order larger than that of the electromagnetic penguin diagrams.     

A Phenomenological Expression for Deuteron Electromagnetic Form Factors Based on Perturbative QCD Predict ions

For deuteron's electromagnetic form factors, perturbative QCD (pQCD) predicts that G₀₀⁺ becomes the dominate helicity amplitude and G₊₀⁺ and G_{+ -}⁺ are suppressed by factors A_QCD/Q and A_QCD²/Q² at large Q² respectively. We try to discuss the higher-order corrections beyond the pQCD asymptotic predictions by interpolating an analytical form to the intermediate energy region. From fitting the data, our results show that the helicity-zero to zero matrix element G₀₀⁺ dominates the gross structure function A(Q²) in both the large and intermediate energy regions. It is a good approximation for G_{+ -}⁺ to ignore the higher-order contributions and the higher-order corrections to G₊₀⁺ should be taken into account due to sizeable contributions in the intermediate energy region.     

Relationship between electronic and crystal structure in Cu–Ni–Co–Mn–O spinels: Part B: Binding energy anomaly in Cu photoemission spectrum

In very rare circumstances, X-ray photoemission spectra of copper in spinel oxides exhibit a “negative binding energy shift”. The origin of such an anomalous XPS chemical shift was investigated. A metastable Ni_0.48Co_0.24Cu_0.6+xMn_1.68−xO₄ (0 < x < 0.6) spinel was fabricated at 600 °C using a low-temperature solution technique. The binding energy of the 2p_3/2 level of copper (930.8 eV) is found 1.9 eV lower than that of Cu⁰ (932.7 eV). XPS and EXAFS studies revealed that the post-thermal annealing between 600 and 800 °C undergoes an irreversible cubic-to-tetragonal phase transformation through oxidation–reduction reaction Cu¹⁺ + Mn⁴⁺  Cu²⁺ + Mn³⁺, and only tetrahedral Cu¹⁺ species in the cubic spinel shows this anomalous chemical shift. The negative shift of the core levels was correlated to an equal shift of the Cu 3d valence band levels. XPS valence bands from the samples annealed at different temperatures were compared to DOS calculations. The DOS computations were performed with FEFF-8.1 code using experimental crystal parameters established by the EXAFS analysis. It was found that the tetrahedral Cu¹⁺ in the 600 °C annealed sample exhibits localization of the 3d orbitals showing behavior characteristic to zinc. The completely filled and isolated 3d electron shell appears as a false valence band edge in the XPS spectrum. The position of the Cu 3d, and other core levels, is established by oxygen pinning the Cu valence band levels and by the fixed value of the p–d gap characteristic to the tetrahedral copper environment in this spinel.     

Exclusive decay of 1 heavy quarkonium into photon and two pions

We study the exclusive decay of 1⁻⁻ heavy quarkonium into one photon and two pions in the kinematic region, where the two-pion system has a invariant mass which is much smaller than the mass of heavy quarkonium. Neglecting effects suppressed by the inverse of the heavy quark mass, the decay amplitude can be factorized, in which the nonperturbative effect related to heavy quarkonium is represented by a non-relativistic QCD matrix element, and that related to the two pions is represented by a distribution amplitude of two gluons in the isoscalar pion pair. By taking the asymptotic form for the distribution amplitude and by using chiral perturbative theory we are able to obtain numerical predictions for the decay. Numerical results show that the decay of J/ψ can be observed at BEPC and at CESR. Experiment observation of this process in this kinematic region at BEPC and CESR can provide information about how gluons are converted into the two pions and may supply a unique approach to study I=0 s-wave ππ scattering.     

Out-of-time-order correlators in the one-dimensional XY model

We study the behavior of information spreading in the XY model, using out-of-time-order correlators(OTOCs). The effects of anisotropic parameter γ and external magnetic field λon OTOCs are studied in detail within thermodynamical limits. The universal form which characterizes the wavefront of information spreading still holds in the XY model. The butterfly speed vBdepends on(γ, λ). At a fixed location, the early-time evolution behavior of OTOCs agrees with the results of the Hausdorff–Baker–Campbell expansion. For long-time evolution,OTOCs with local operators decay as for power law t-1, but those with nonlocal operators show different and nontrivial power law behaviors. We also observe temperature dependence for OTOCs when(γ=0, λ=1). At low temperature, the OTOCs with nonlocal operators show divergence over time.     

Effects of non-standard tri-linear couplings in photon-photon collisions (I) γγ → WW

The effect of anomalous couplings in γγ → W⁺W^t- is studied for different energies of the γγ mode of the next linear collider. The analysis based on the maximum likelihood method exploits the variables in the four-fermion semi-leptonic final state. Polarized differential cross sections based on the complete set of diagrams for these channels with the inclusion of anomalous couplings are used and compared to an approximation based on γγ → W⁺W^t- with full spin correlations. To critically compare these results with those obtained in e⁺e^t- we perform an analysis based on the complete calculation of the four-fermion semi-leptonic final state. The anomalous couplings that we consider are derived from the next-to-leading order operators in the non-linear realization of symmetry breaking.