17051703
Quantum-chromodynamic potential model for light-heavy quarkonia and the heavy quark effective theory.
We have investigated the spectra of light-heavy quarkonia with the use of a quantum-chromodynamic potential model, which is similar to that used earlier for heavy quarkonia. An essential feature of our treatment is the inclusion of the one-loop radiative corrections to the quark-antiquark potential, which contribute significantly to the spin splitting among the quarkonium energy levels. Unlike [ital c[bar c]] and [ital b[bar b]], the potential for a light-heavy system has a complicated dependence on the light and heavy quark masses [ital m] and [ital M], and it contains a spin-orbit mixing term. We have obtained excellent results for the observed energy levels of [ital D][sup 0], [ital D][sub [ital s]], [ital B][sup 0], and [ital B][sub [ital s]], and we are able to provide predicted results for many unobserved energy levels. Our potential parameters for different quarkonia satisfy the constraints of quantum chromodynamics. We have also used our investigation to test the accuracy of the heavy quark effective theory. We find that the heavy quark expansion yields generally good results for the [ital B][sup 0] and [ital B][sub [ital s]] energy levels provided that [ital M][sup [minus]1] and [ital M][sup [minus]1] ln [ital M] corrections are taken into account more » in the quark-antiquark interactions. It does not, however, provide equally good results for the energy levels of [ital D][sup 0] and [ital D][sub [ital s]], which indicates that the effective theory cannot be applied accurately to the [ital c] quark. « less
6552264
Nonsingular potential model for heavy quarkonia.
A nonsingular potential model for heavy quarkonia is described which does not require recourse to an illegitimate perturbative treatment for the investigation of quarkonium spectra. Our overall results for the energy levels, the leptonic widths, and the E1 transition widths are in very good agreement with the experimental data for bb-bar and they are reasonably good for cc-bar. We also find that the confining part of the quarkonium potential is scalar-vector exchange rather than the currently favored scalar exchange.
123149979
Ghost-field formalism for vector particles
122039483
Supplementary Conditions in the Quantized Gravitational Theory
120228440
Regularization of fermion loops in gauge models
Fermion loops in gauge models with ${\ensuremath{\gamma}}_{5}$ couplings cannot be regularized in a gauge-invariant manner either by the method of auxiliary fields or by dimensional continuation. It is shown that in the absence of a gauge-invariant regularization procedure, the method of auxiliary fields can be employed in such a way that non-gauge-invariance is confined to the renormalization constants. It is thus possible to obtain gauge-invariant renormalized results as well as resolve anomalies without the use of Ward's identities. Explicit calculations are carried out for the self-energy and triangle diagrams with fermion loops in the Appelquist-Quinn model. The present treatment is also compared with naive dimensional regularization for the ${\ensuremath{\gamma}}_{5}$ couplings.
1943581
Quark confinement in quantum chromodynamics.
A quark-confinement mechanism inspired by renormalization-group-improved perturbative quantum chromodynamics is proposed. We obtain a quark-antiquark confining potential in the lowest approximation, show that it yields reasonable results for the bb-bar and cc-bar spin-averaged energy levels, and comment on the significance of the higher-order effects.
20187829
Calculation of the pion's quark distribution amplitude in lattice QCD with dynamical fermions.
We present a calculation of the pion decay constant and of the second moment of the quark distribution amplitude of the pion within full lattice QCD. Measurements are made on 12{sup 3}{times}24 and 16{sup 3}{times}32 lattices, using two flavors of Wilson fermion. Different methods used to extract {ital f}{sub {pi}} give consistent results. We find a better signal for the second moment of the distribution amplitude than in previous lattice calculations and obtain results that are significantly smaller than those obtained from sum-rule calculations and previously in (quenched) lattice QCD.
14017597
Bethe-Salpeter amplitudes and density correlations for mesons with Wilson fermions.
We present an investigation of various gauge-invariant definitions of the qq Bethe-Salpeter (BS) amplitude for mesons in lattice QCD, and compare them to the Coulomb and Landau gauge BS amplitudes. We show that the gauge-invariant BS amplitude is considerably broadened by the use of «fat» gauge links (constructed by smearing the links of the original lattice). A qualitative demonstration of the Lorentz contraction of the pion wave function at nonzero momentum is given. We also calculate density-density correlations and discuss the limitations in extracting the charge radius of the pion from these observables. Lastly, the polarization dependence of the BS amplitude for the ρ meson is exhibited, and we extract the relative admixture of l = 0 and l = 2 states showing that simple hydrogenlike wave functions provide a good fit
37920331
Systematics in the volume integrals of the imaginary part of the light ion optical potentials.
A systematic analysis of the imaginary part of the light projectile (A/sub p/ = 1--6) phenomenological optical potentials has been carried out. As a result of this analysis a global formula has been found which describes successfully the volume integrals of the imaginary potential in terms of the projectile energy in the range 0--50 MeV/nucleon and the target and the projectile mass numbers.
7081152
Trajectory modifications in the Glauber model for heavy ions.
Expressions are presented for the modification due to the nuclear potential apart from the Coulomb potential both for the eikonal and the noneikonal trajectories. Calculations for heavy ion total reaction cross sections are performed using these expressions. Results are given for several systems. It is found that the expression used by Cha leads to unrealistic values for the distance of closest approach at small impact parameters at low energies and therefore lead to inaccurate values of the total reaction cross section. The exactly calculated distance of closest approach leads to improved results both for the eikonal and the noneikonal trajectories.
27549292
Isoscalar axial-vector renormalization constant and polarized proton structure function.
The isoscalar axial-vector renormalization constant is reevaluated using the QCD sum-rule method. It is found to be substantially different from the anomaly-free octet axial-vector u¯γμγ5+d¯γμγ5-2s¯γμγ5 coupling. Combining this determination with the known values of the isovector coupling GA and the F/D ratio for the octet current, we find the integral of the polarized proton structure function to be Gp=Fgp1(x)dx=0.135, in agreement with recent measurement by the European Muon Collaboration.