Model of mesons with constituent gluons

A model of mesons composed of a quark, an antiquark, and a gluon is proposed. The binding of the constituents is provided by a confining linear potential between the gluon and the quarks. The lowest states of the model are described, and their relative masses evaluated, for the case of heavy (charmed) quarks, i.e., ccg states

The Gluon Propagator at High Temperature

We study the gluon propagator in Landau gauge in the deconfined phase of $SU(2)$ gauge theory. From the long-distance behaviour of correlation functions of temporal and spatial components of the gauge fields we extract electric ($m_e$) and magnetic ($m_m$) screening masses. For temperatures larger than twice $T_c$ we find no additional temperature dependence in $m_e(T)/T$, while $m_m(T)/T$ drops with increasing temperature. The decrease is consistent with the expected behaviour, $m_m(T) \sim g^2(T)T$. We find $m_e(T) = 2.484(52)T$ and $m_m(T) = 0.466(15) g^2(T) T$.Comment: 11 pages, TEX-file, 5 PS-figur

Lattice Heavy Quark Effective Theory and the Isgur-Wise function

We compute the Isgur-Wise function using heavy quark effective theory formulated on the lattice. The non-relativistic kinetic energy term of the heavy quark is included to the action as well as terms remaining in the infinite quark mass limit. The classical velocity of the heavy quark is renormalized on the lattice and we determine the renormalized velocity non-perturbatively using the energy-momentum dispersion relation. The slope parameter of the Isgur-Wise function at zero recoil is obtained at $\beta=6.0$ on a $24^3\times 48$ lattice for three values of $m_{Q}$.Comment: 14 pages of A4 format and 8 figures in one uuencoded postscript fil

B meson form factors from HQET simulations

We use simulations of heavy quark effective field theory to calculate the Isgur-Wise function, and we demonstrate the feasibility of calculating the matrix element for the B \to \pi + \leptons decay in the lattice heavy quark effective theory (HQET).Comment: 3 pages, 2 figures, talk presented at the lattice 97 conferenc

Thermal Dileptons from a Nonperturbative Quark-Gluon Phase

Assuming that gluon condensates are important even above the deconfining phase transition, we develop a model for the dilepton yield from a quark gluon plasma. Using a simple fire ball description of a heavy ion collision, and various estimates of the strengths of the gluon condensates, we compare our predicted dilepton yields with those observed in the CERES and HELIOS experiments at CERN. The simple model gives an adequate description of the data, and in particular it explains the observed considerable enhancement of the yield in the low mass region.Comment: 7 pages, 6 figures, reference adde

Gauge Boson Masses in the 3-d, SU(2) Gauge-Higgs Model

We study gauge boson propagators in the symmetric and symmetry broken phases of the 3-d, $SU(2)$ gauge-Higgs model. Correlation functions for the gauge fields are calculated in Landau gauge. They are found to decay exponentially at large distances leading to a non-vanishing mass for the gauge bosons. We find that the W-boson screening mass drops in the symmetry broken phase when approaching the critical temperature. In the symmetric phase the screening mass stays small and is independent of the scalar--gauge coupling (the hopping parameter). Numerical results coincide with corresponding calculations performed for the pure gauge theory. We find $m_w = 0.35(1)g^2T$ in this phase which is consistent with analytic calculations based on gap equations. This is, however, significantly smaller than masses extracted from gauge invariant vector boson correlation functions. As internal consistency check we also have calculated correlation functions for gauge invariant operators leading to scalar and vector boson masses. Finite lattice size effects have been systematically analyzed on lattices of size $L^2\times L_z$ with $L=4-24$ and $L_z = 16 - 128$.Comment: 20 pages, LaTeX2e File, 8 Postscript figure

A Study of Gluon Propagator on Coarse Lattice

We study gluon propagator in Landau gauge with lattice QCD, where we use an improved lattice action. The calculation of gluon propagator is performed on lattices with the lattice spacing from 0.40 fm to 0.24 fm and with the lattice volume from $(2.40 fm)^4$ to $(4.0 fm)^4$. We try to fit our results by two different ways, in the first one we interpret the calculated gluon propagators as a function of the continuum momentum, while in the second we interpret the propagators as a function of the lattice momentum. In the both we use models which are the same in continuum limit. A qualitative agreement between two fittings is found.Comment: Revtex 14pages, 11 figure