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.
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.
119431536
Meson-meson scattering in relativistic constraint dynamics
Dirac's relativistic constraint dynamics have been successfully applied to obtain a covariant nonperturbative description of QED and QCD bound states. We use this formalism to describe a microscopic theory of meson-meson scattering as a relativistic generalization of the nonrelativistic quark-interchange model developed by Barnes and Swanson.
119205968
The Momentum Kick Model Description of the Near-Side Ridge and Jet Quenching
In central high-energy heavy-ion collisions, jets are produced in nucleon-nucleon collisions and they interact with the dense medium produced in the interacting region. Depending on the relative azimuthal angle relative to the trigger particle, observed high-pt jets can be classified as near-side jets or away-side jets. An away-side jet is associated with a broad cone of particles pointing azimuthally opposite to the trigger particle direction. The strong attenuation of the away-side jet in its passage through the produced dense matter is one of the many notable experimental observations in relativistic heavy-ion collisions and is a signature for the production of the strongly-coupled quark-gluon plasma [1, 2, 3, 4]. On the other hand, a near-side jet is characterized by the presence of associated particles within a narrow azimuthal angle along the trigger particle direction. It retains many of the characteristics of the associated fragmentation products as those of a jet in pp and peripheral heavy-ion collisions. The near-side jet occurs when the high-pt jet emerges near the surface of the produced parton medium.
119274040
Wigner function of produced particles in string fragmentation
I show that quantum chromodynamics in four dimensions (QCD4) with transverse confinement can be approximately compactified into QCD2 with a transverse quark mass m{sub T} that is obtained by solving a set of coupled transverse eigenvalue equations. In the limits of a strong coupling and a large number of flavors, QCD2 further admits Schwinger QED2-type bosonized solutions. I therefore examine phenomenologically the space-time dynamics of particles produced in string fragmentation by studying the Wigner function of bosons produced in Schwinger QED2, which mimics many features of string fragmentation in quantum chromodynamics. I find that particles with momenta in different regions of the rapidity plateau are produced at the initial moment of string fragmentation as a quark pulls away from an antiquark at high energies, in contrast to classical depictions of string fragmentation with longitudinal space-momentum-time ordering.
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.
119276754
Can the nearly conformal sextet gauge model hide the Higgs impostor
Abstract New results are reported from large scale lattice simulations of a frequently discussed strongly interacting gauge theory with a fermion flavor doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. We find that the chiral condensate and the mass spectrum of the sextet model are consistent with chiral symmetry breaking in the limit of vanishing fermion mass. In contrast, sextet fermion mass deformations of spectral properties are not consistent with leading conformal scaling behavior near the critical surface of a conformal theory. A recent paper could not resolve the conformal fixed point of the gauge coupling from the slowly walking scenario of a very small nearly vanishing β -function (DeGrand et al. [3] ). It is argued that overall consistency with our new results is resolved if the sextet model is close to the conformal window, staying outside with a very small non-vanishing β -function. The model would exhibit then the simplest composite Higgs mechanism leaving open the possibility of a light scalar state with quantum numbers of the Higgs impostor. It would emerge as the pseudo-Goldstone dilaton state from spontaneous symmetry breaking of scale invariance. We will argue that even without association with the dilaton, the scalar Higgs-like state can be light very close to the conformal window. A new Higgs project of sextet lattice simulations is outlined to resolve these important questions.
118711171
A novel algorithm for computing quark propagators for lattice hadron spectroscopy
We report on our progress in computing the excitation spectrum in Lattice QCD. We focus on the isospin 0, 1 and 2 channels using the stochastic LapH algorithm for the quark propagators. For the isospin-0 channel, a new glueball operator constructed from the stochastic LapH operator is included in the variational basis along with the isoscalar meson and pi-pi operators. A representative signal for each channel is presented and the feasibility of extending the calculations to larger lattices is discussed.
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.
118877995
Toward the minimal realization of a light composite Higgs
Work in progress is reported on a particularly interesting gauge theory with a fermion doublet in the two-index symmetric (sextet) representation of the SU(3) color gauge group. Extending previous studies we outline our strategy as we investigate Goldstone dynamics and Electroweak scale setting from chiral symmetry breaking ($\chi$ SB), test the GMOR relation from the spectrum of the Dirac operator and the related chiral condensate, begin to develop and test mixed action based improved analysis of $\chi$ SB with new run plans at fixed topology to cross over from the p-regime to the epsilon-regime of $\chi$ SB, continue to pursue the light $0^{++}$ scalar and its relation to the dilaton, and probe the scale-dependent running coupling from the perturbative UV scale to the scale of chiral symmetry breaking. Our observations suggest that the model is very close to the conformal window and a light composite scalar, perhaps the Higgs impostor with or without dilaton-like interpretation, appears to emerge with $0^{++}$ quantum numbers. The lightest baryon of the model on the 3 TeV scale has intriguing implications.
119243656
Excited-state hadron masses using the stochastic LapH method
Progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Large sets of spatially-extended hadron operators are used. The need for multi-hadron operators in addition to single-hadron operators is emphasized, necessitating the use of a new stochastic method of treating the low-lying modes of quark propagation which exploits Laplacian Heaviside quark-field smearing. A new glueball operator is tested and computing the mixing of this glueball operator with a quark-antiquark operator and multiple two-pion operators is shown to be feasible. Some of our initial results show warning signs about extracting high-lying resonance energies using only single-hadron operators.