118924601
Heavy quarkonia in quark-gluon plasma
Q in quenched QCD, we study the binding energies and wave functions of heavy quarkonia in a quark-gluon plasma. By minimizing the grand potential in a simplified schematic model, we find that the proper color-singlet Q- ¯ Q potential can be obtained from the total internal energy U1 by subtracting the gluon internal energy contributions. We carry out this subtraction in the local energy-density approximation in which the gluon energy density can be related to the local gluon pressure by the quark-gluon plasma equation of state. We find in this approximation that the proper color-singlet Q- ¯ Q potential is approximately F1 for T ∼ Tc and it changes to 3 F1 + 1 U1 at high temperatures. In this potential model, the J/ ψ is weakly bound above the phase-transition temperature Tc, and it dissociates spontaneously above 1.62Tc, whereas χc and ψ � are unbound in the quark-gluon plasma. The bottomium states ϒ, χb ,a ndϒ � are bound in the quark-gluon plasma and they dissociate at 4.1Tc, 1.18Tc, and 1.38Tc respectively. For comparison, we evaluate the heavy quarkonium binding energies also in other models using the free energy F1 or the total internal energy U1 as the Q- ¯ Q potential. The comparison shows that the model with the new Q- ¯ Q potential proposed here gives dissociation temperatures that agree best with those from spectral function analyses. We evaluate the cross section for σ (g + J/ ψ → c + ¯ c) and its inverse process to determine the J/ ψdissociation width and the rate of J/ ψ production by recombining c and ¯ c in the quark-gluon plasma.
119074511
Tests of two-body Dirac equation wave functions in the decays of quarkonium and positronium into two photons
Two-body Dirac equations of constraint dynamics provide a covariant framework to investigate the problem of highly relativistic quarks in meson bound states. This formalism eliminates automatically the problems of relative time and energy, leading to a covariant three dimensional formalism with the same number of degrees of freedom as appears in the corresponding nonrelativistic problem. It provides bound state wave equations with the simplicity of the nonrelativistic Schr\"odinger equation. Here we begin important tests of the relativistic 16 component wave function solutions obtained in a recent work on meson spectroscopy, extending a method developed previously for positronium decay into two photons. Preliminary to this we examine the positronium decay in the $^{3}P_{0,2}$ states as well as the $^{1}S_{0}$. The two-gamma quarkonium decays that we investigate are for the ${\ensuremath{\eta}}_{c}$, ${\ensuremath{\eta}}_{c}^{\ensuremath{'}}$, ${\ensuremath{\chi}}_{c0}$, ${\ensuremath{\chi}}_{c2}$, ${\ensuremath{\pi}}^{0}$, ${\ensuremath{\pi}}_{2}$, ${a}_{2}$, and ${f}_{2}^{\ensuremath{'}}$ mesons. Our results for the four charmonium states compare well with those from other quark models and show the particular importance of including all components of the wave function as well as strong and c.m. energy dependent potential effects on the norm and amplitude. The results for the ${\ensuremath{\pi}}^{0}$, although off the experimental rate by 13%, are much closer than the usual expectations from a potential model. We conclude that the two-body Dirac equations lead to wave functions which provide good descriptions of the two-gamma decay amplitude and can be used with some confidence for other purposes.
6390507
Quantum Treatment of the Multiple Scattering and Collective Flow in Intensity Interferometry
We apply the path‐integral method to study the multiple scattering and collective flow in intensity interferometry in high‐energy heavy‐ion collisions. We show that the Glauber model and eikonal approximation in an earlier quantum treatment are special examples of the more general path‐integral method. The multiple scattering and collective flow lead essentially to an initial source at a shifted momentum, with a multiple collision absorption factor that depends on the pion absorption cross section and a phase factor that depends on the deviations of the in‐medium particle momenta from their asymptotic values.
118543230
Extended Glauber Model of Antiproton-Nucleus Annihilation for All Energies and Mass Numbers
Previous analytical formulas in the Glauber model for high-energy nucleus-nucleus collisions developed by Wong are utilized and extended to study Antiproton-nucleus annihilations for both high and low energies, after taking into account the effects of Coulomb and nuclear interactions, and the change of the antiproton momentum inside a nucleus. The extended analytical formulas capture the main features of the experimental antiproton-nucleus annihilation cross sections for all energies and mass numbers. At high antiproton energies, they exhibit the granular property for the lightest nuclei and the black-disk limit for the heavy nuclei. At low antiproton energies, they display the effect of the antiproton momentum increase due to the nuclear interaction for the light nuclei, and the effect of the magnification due to the attractive Coulomb interaction for the heavy nuclei.
36760880
Potential Models and Lattice Gauge Current-Current Correlators
We compare current-current correlators in lattice gauge calculations with correlators in different potential models for a pseudoscalar charmonium in the quark-gluon plasma. An important ingredient in the evaluation of the current-current correlator in the potential model is the basic principle that, out of the set of continuum states, only resonance states and Gamow states with lifetimes of sufficient magnitudes can propagate as composite objects and can contribute to the current-current correlator. When the contributions from the bound states and continuum states are properly treated, the potential model current-current correlators obtained with the potential proposed by Wong [Phys. Rev. C 72, 034906 (2005)] are consistent with the lattice gauge correlators. The proposed potential model thus gains support to be a useful tool to complement lattice gauge calculations for the study of QQ{bar} states at high temperatures.
119115984
Singularity structures in Coulomb-type potentials in two-body Dirac equations of constraint dynamics
Two-body Dirac equations (TBDE) of Dirac's relativistic constraint dynamics have been successfully applied to obtain a covariant nonperturbative description of QED and QCD bound states. Coulomb-type potentials in these applications lead naively in other approaches to singular relativistic corrections at short distances that require the introduction of either perturbative treatments or smoothing parameters. We examine the corresponding singular structures in the effective potentials of the relativistic Schroedinger equation obtained from the Pauli reduction of the TBDE. We find that the relativistic Schroedinger equation leads in fact to well-behaved wave function solutions when the full potential and couplings of the system are taken into account. The most unusual case is the coupled triplet system with S=1 and L={l_brace}(J-1),(J+1){r_brace}. Without the inclusion of the tensor coupling, the effective S-state potential would become attractively singular. We show how including the tensor coupling is essential in order that the wave functions be well-behaved at short distances. For example, the S-state wave function becomes simply proportional to the D-state wave function and dips sharply to zero at the origin, unlike the usual S-state wave functions. Furthermore, this behavior is similar in both QED and QCD, independent of the asymptotic freedom behavior of the assumed QCDmore » vector potential. Light- and heavy-quark meson states can be described well by using a simplified linear-plus-Coulomb-type QCD potential apportioned appropriately between world scalar and vector potentials. We use this potential to exhibit explicitly the origin of the large pi-rho splitting and effective chiral symmetry breaking. The TBDE formalism developed here may be used to study quarkonia in quark-gluon plasma environments.« less
118432510
Conformal finite size scaling of twelve fermion flavors
Extended simulation results and their analysis are reported in a strongly coupled gauge theory with twelve fermion flavors in the fundamental SU(3) color representation. The conformality of the model is probed using mass deformed conformal finite size scaling (FSS) theory driven by the fermion mass anomalous dimension. Two independent conformal FSS fitting procedures are used in the analysis. The first one deploys physics motivated scaling functions, complemented by a second fitting procedure with spline based general B-forms for the scaling functions. The results at fixed gauge coupling show unresolved problems with the conformal hypothesis.
119238736
Phase shift with LapH propagators
The pion-pion scattering phase shift is computed using LapH propagators. The LapH method for computing quark propagators is used to form two-particle correlation functions with a number of different operators. Excited state energies of two-particle states on 2+1 dynamical, anisotropic lattices (mp 390 MeV ) are computed to determine the phase shift in the I = 2 channel. The signal for t-to-t diagrams for the I = 0 channel are also presented to demonstrate the efficacy of the stochastic LapH method.
118435845
The excited hadron spectrum in lattice QCD using a new method of estimating quark propagation
Progress in determining the spectrum of excited baryons and mesons in lattice QCD is described. Large sets of carefully‐designed hadron operators have been studied and their effectiveness in facilitating the extraction of excited‐state energies is demonstrated. A new method of stochastically estimating the low‐lying effects of quark propagation is proposed which will allow reliable determinations of temporal correlations of single‐hadron and multi‐hadron operators.
118639009
Multi‐hadron states in Lattice QCD spectroscopy
The ability to reliably measure the energy of an excited hadron in Lattice QCD simulations hinges on the accurate determination of all lower‐lying energies in the same symmetry channel. These include not only single‐particle energies, but also the energies of multi‐hadron states. This talk deals with the determination of multi‐hadron energies in Lattice QCD. The group‐theoretical derivation of lattice interpolating operators that couple optimally to multi‐hadron states is described. We briefly discuss recent algorithmic developments which allow for the efficient implementation of these operators in software, and present numerical results from the Hadron Spectrum Collaboration.
118614393
Two-particle Correlation Functions with Distilled Propagators
Carnegie Mellon UniversityE-mail:chikhimw@cmu.eduFor the Hadron Spectrum CollaborationCorrelation functions of the simplest multi-particle state will be presented using distilled quarkpropagators. The I =2 ππstate can be simulated without computing disconnected diagrams andthus is the simplest two-particle state that can be studied with quark sources placed on a singletime-slice alone. We study the quality of the signals of thisππcorrelation function using thequark-smearingguided distillation method. Results will be presented for ππcorrelation functionscomputed on dynamical, anisotropic lattices.The XXVII International Symposium on Lattice Field Theory -LAT2009July 26-31 2009Peking University, Beijing, China