625025
Relativistic two-photon and two-gluon decay rates of heavy quarkonia.
The decay rates of {ital c{bar c}} and {ital b{bar b}} through two-photon or two-gluon annihilations are obtained by using totally relativistic decay amplitudes and a sophisticated quantum-chromodynamic potential model for heavy quarkonia. Our results for the photonic and gluonic widths of the {sup 1}{ital S}{sub 0}, {sup 3}{ital P}{sub 0}, and the {sup 3}{ital P}{sub 2} states are in excellent agreement with the available experimental data. The procedures and mathematical techniques used by us for the treatment of the fermion-antifermion bound states are also applicable to other decay processes. {copyright} {ital 1996 The American Physical Society.}
122167852
MULTIPLE PHOTON PRODUCTION IN QUANTUM ELECTRODYNAMICS
Multiple production of photons in high-energy processes in quantum electrodynamics is investigated, and the electron-positron annihilation is specially discussed in detail. It is found that at very high energies in cosmic rays, multiple production of up to four or five observable photons can easily take place. But, the probability, according to quantum electrodynamics, for the multiple production of a larger number of observable photons is quite small.
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.
122156675
Relativistic Hadron Model with Intrinsic Mass Splittings
A simple mechanism for the $\mathrm{SU}(3)$-symmetry breaking in strong interactions is introduced by using the formalism of the multispinor field equations, which avoids the use of physical quarks but has resemblance to the quark model. The resulting treatment leads to the Gell-Mann-Okubo mass formula for baryons, but not for mesons. It yields approximate values of -19.5\ifmmode^\circ\else\textdegree\fi{} and 33\ifmmode^\circ\else\textdegree\fi{} for the $\ensuremath{\eta}\ensuremath{-}{\ensuremath{\eta}}^{\ensuremath{'}}$ and $\ensuremath{\varphi}\ensuremath{-}\ensuremath{\omega}$ mixing angles, respectively, and also provides a reasonable explanation for the intermultiplet meson mass formula $m_{K}^{}{}_{}{}^{2}\ensuremath{-}m_{\ensuremath{\pi}}^{}{}_{}{}^{2}=m_{{K}^{*}}^{}{}_{}{}^{2}\ensuremath{-}m_{\ensuremath{\rho}}^{}{}_{}{}^{2}$.
120383870
Higgs model with ghost-field formalism
The Higgs model for the interaction of vector and scalar fields is treated by means of the ghost-field formalism, which preserves the unitarity of the scattering operator as well as simplifies the renormalization procedure. Our ghost-field formalism has some similarity to the ${R}_{\ensuremath{\xi}}$ formalism with $\ensuremath{\xi}=1$, but it does not require the introduction of the so-called gauge-compensating terms. Applications to the second-order self-energy of a scalar particle and to the fourth-order scattering of vector particles are discussed.
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
31179622
Elastic scattering of alpha particles from 209Bi at 24.8, 28.5, 34.7, 38.8, and 69.5 MeV.
Differential cross sections for the elastic scattering of alpha particles from {sup 209}Bi have been measured over a wide angular range at a number of energies between 24 and 70 MeV. The present data along with existing data in this energy range have been analyzed using the optical model with both phenomenological and double-folded potentials. The application of the dispersion relation of Mahaux, Ng{cflx o}, and Satchler allows a reproduction of the observed energy dependence of the real part of the potential. A nearside-farside decomposition of the data clearly reveals large-angle Fraunhoefer oscillations. The inelastic cross sections at 69.5 MeV have also been measured and the deformation lengths obtained from a distorted-wave Born analysis are consistent with values reported in the literature.
40514876
Hadronic correlation functions in the QCD plasma phase.
We present results for static hadronic correlation functions in the high-temperature phase of QCD with four flavors of dynamical quarks. We confirm chiral-symmetry restoration through the degeneracies of the spectrum of screening lengths. We also find that the screening lengths for the {rho} and {ital N} channels at {ital T}{approx gt}1.2{ital T}{sub {ital c}} are close to that in a free quark gas.
17011670
Color-octet contributions to J/ psi hadroproduction at fixed target energies.
We investigate the integrated cross section for forward {ital J}/{psi} production in proton-proton and pion-proton collisions at center-of-mass energies up to 60 GeV. We find that color-octet contributions to the cross section are crucially important, and their inclusion produces a very good description of the data. Since the values of nonperturbative matrix elements are fixed by other experiments, these predictions are parameter-free. {copyright} {ital 1996 The American Physical Society.}
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
12293063
Detection of ultrahigh-energy radiation from Scorpius X-1: Ooty observations during 1984-1987.
A detailed study of showers arriving from the direction of Scorpius X-1 has shown strong evidence for emission of ultrahigh-energy radiation from Scorpius X-1 during the period 4 March-2 May 1986. 178 showers were observed in the source bin againat an expected background of 122.9. The chance probability for observing this excess has been estimated from simulations to be less than 10 -3 . The flux observed during this period was (6.4±1.6)×10 -12 cm -2 s -1 at energies >2.5×10 14 eV, corresponding to a luminosity of 2×10 35 ergs s -1 .