Momentum Kick Model Analysis of PHENIX Near-Side Ridge Data and Photon Jet
We analyze PHENIX near-side ridge data for central Au + Au collisions at √S NN = 200 GeV with the momentum-kick model, in which a near-side jet emerges near the surface, kicks medium partons, loses energy, and fragments into the trigger particle and fragmentation products. The kicked medium partons subsequently materialize as the observed ridge particles, which carry direct information on the early parton momentum distribution and the magnitude of the momentum kick. We find that the PHENIX ridge data can be described well by the momentum-kick model and the extracted early partons momentum distribution has a thermal-like transverse distribution and a rapidity plateau structure. We also find that the parton-parton scattering between the jet parton and the medium parton involves the exchange of a nonperturbative pomeron, for jet partons in momentum range considered in the near-side ridge measurements.

title: Tests of two-body Dirac equation wave functions in the decays of quarkonium and positronium into two photons
abstract: 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.

title: Potential Models and Lattice Gauge Current-Current Correlators
abstract: 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 [ (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.

title: Singularity structures in Coulomb-type potentials in two-body Dirac equations of constraint dynamics
abstract: 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

title: Extended Glauber Model of Antiproton-Nucleus Annihilation for All Energies and Mass Numbers
abstract: 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.

title: Quantum Treatment of the Multiple Scattering and Collective Flow in Intensity Interferometry
abstract: 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.

title: Group-theoretical construction of finite-momentum and multi-particle operators for lattice hadron spectroscopy
abstract: Determining the spectrum of hadronic excitations from Monte Carlo simulations requires the use of interpolating operators that couple to multi-particle states. Recent algorithmic advances have made the inclusion of multi-hadron operators in spectroscopy calculations a practical reality. In this talk, a procedure for constructing a set of multi-hadron interpolators that project onto the states of interest is described. To aid in the interpretation of simulation data, operators are designed to transform irreducibly under the lattice symmetry group. The identification of a set of optimal single-hadron interpolators for states with non-zero momenta is an essential intermediate step in this analysis.

title: The running coupling of 8 flavors and 3 colors
abstract: A bstractWe compute the renormalized running coupling of SU(3) gauge theory coupled to Nf = 8 flavors of massless fundamental Dirac fermions. The recently proposed finite volume gradient flow scheme is used. The calculations are performed at several lattice spacings allowing for a controlled continuum extrapolation. The results for the discrete β-function show that it is monotonic without any sign of a fixed point in the range of couplings we cover. As a cross check the continuum results are compared with the well-known perturbative continuum β-function for small values of the renormalized coupling and perfect agreement is found.

title: Can the Higgs Impostor Hide Near the Conformal Window
abstract: We present a minimal candidate model for the composite Higgs mechanism with a fermion doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. The model is known to be close to the conformal window with a small β-function. Chiral symmetry breaking with vacuum condensate becomes the origin of electroweak symmetry breaking from compositeness. Close to the conformal window, a light scalar state with Higgs quantum numbers is emerging. Associations with the recently observed 126 GeV Higgs boson, or with a dilaton state from broken scale invariance, are subjects of ongoing investigations.

title: The gradient flow running coupling scheme
abstract: The Yang-Mills gradient flow in finite volume is used to define a running coupling scheme. As our main result the discrete β -function, or step scaling function, is calculated for scale change s = 3/2 at several lattice spacings for SU(3) gauge theory coupled to N f = 4 fundamental massless fermions. The continuum extrapolation is performed and agreement is found with the continuum perturbative results for small renormalized coupling. The case of SU(2) gauge group is briefly commented on.

title: Twelve fundamental and two sextet fermion flavors
abstract: We report extended simulation results and their new analysis in two important gauge theories with twelve fermion flavors in the fundamental SU(3) color representation and two fermions in the sextet representation. We probe the $N_f=12$ model with respect to the conformal window using mass deformed finite size scaling (FSS) theory driven by the fermion mass anomalous dimension. Our results at fixed gauge coupling show problems with the conformal scenario of the $N_f=12$ model. In the sextet model with two flavors, under the conformal hypothesis, we determine large values for the anomalous fermion mass dimension with $\gamma\geq 1$. Since our sextet analysis favors the chiral symmetry breaking hypothesis without conformality, the large exponent $\gamma$ could play an important role in understanding the composite Higgs mechanism. The new results discussed here include our extended data sets and exceed what was presented at the conference.