Related papers: Gluon Condensate from Superconvergent QCD Sum Rule
We consider various special cases of gluon condensates at finite temperature. The gluon condensate for an ideal gas of gluons with a given vacuum expectation value is introduced for the sake of comparison with that calculated using the…
The mass of the lowest scalar glueball is discussed by using QCD sum rules. We find that the glueball mass is sensitive to the choice of moments and slightly depends on the radiative corrections. With the help of suitable moments and…
The quark <\bar\psi \psi> and gluon <F_{\mu\nu}F^{\mu\nu}> vacuum expectation values are non-vanishing at low orders in \alpha_s when the perturbative ground state includes quark and gluon pairs. This offers possibilities of studying the…
Equation for the sum of BFKL pomeron fan diagrams is rederived by direct summation and solved numerically for rapidities $y\leq 50$. At high rapidities y>20 the resulting cross-sections for the scattering of a longitudinally polarized…
Based on the quark propagator in the instanton dilute liquid approximation, we calculate analytically the quark condensate $<\bar{q}q>$, the mixed quark gluon condensate $g_{s}<\bar{q}G_{\mu\nu}\sigma^{\mu\nu}q>$ and the four quark…
We consider diagonal and non-diagonal QCD sum rules for the ground state heavy baryons to leading order in $1/m_Q$ and at next-to-leading order in $\alpha_S$. In the non-diagonal case we evaluate the eight different two-loop diagrams which…
Gluons dominate the proton behavior at high energy collisions, they can be condensed at ultra high energy. The collisions of the accelerated high energy protons with interplanetary matter in cosmic rays will produce a huge number of…
We investigate the momentum dependence of the g*-g-eta' vertex form factor in the presence of the nonperturbative QCD vacuum condensate. The behaviour of this form factor is crucial for, among other things, some proposed mechanisms devised…
We evaluate the $\pi N$ coupling constant using a QCD sum rule based on the pion-to-vacuum matrix element of the correlator of two interpolating nucleon fields. The part of the correlator with Dirac structure $k\llap/\gamma_5$ is used,…
For special kinematic configurations involving a single momentum scale, certain standard relations, originating from the Slavnov-Taylor identities of the theory, may be interpreted as ordinary differential equations for the ``kinetic term''…
We study the process $qq\rightarrow qqg$ at lowest order in QCD perturbation theory to understand gluon radiation in the fragmentation region of relativistic heavy-ion collisions. We arrive at a formula for gluon multiplicity that…
The free energy density, or pressure, of QCD has at high temperatures an expansion in the coupling constant g, known so far up to order g^5. We compute here the last contribution which can be determined perturbatively, g^6 ln(1/g), by…
We discuss the relationship between the large order behavior of the perturbative series for the average plaquette in pure gauge theory and singularities in the complex coupling plane. We discuss simple extrapolations of the large order for…
The colored objects -- quarks and gluons -- being confined in a small volume $V\sim R_0^3,$ $R_0\sim 0.5$fm inside the QCD bound state get there not small masses $m_{q\bar q}\sim 1$GeV, $m_g\sim 0.5$GeV. This drastically simplifies the QCD…
We prove a theorem in QCD stating that in the limit of strong coupling, $g\to\infty$, the observed spectrum of glueballs in QCD is the same of a pure Yang-Mills theory, being mixing effects due to the next-to-leading order. A full effective…
Using Mandelstam's approximation to the gluon Dyson-Schwinger equation we calculate the gluon self-energy in a renormalisation group invariant fashion. We obtain a non-perturbative $\beta $ function. The scaling behaviour near the…
In this paper, we study instanton contributions to the correlator of the hybrid current $g\bar q \sigma_{\mu\nu}G^a_{\nu\mu}T^a q$. These contributions are then included in a QCD sum-rule analysis of the isoscalar $0^{++}$ hybrid mass. We…
We investigate the a0-omega-gamma vertex and estimate the coupling constant in the framework of the light cone QCD sum rules. We compare our result with the value of the coupling constant was calculated in the QCD sum rules.
We study the properties of the QCD vacuum in the dual Ginzburg-Landau theory, where QCD-monopole condensation leads to the linear confinement potential. Using the effective potential, we find monopole dominance for chiral-symmetry breaking.…
We use QCD sum rules to study the recently observed meson $Z^+(4430)$, considered as a $D^*D_1$ molecule with $J^{P}=0^{-}$. We consider the contributions of condensates up to dimension eight and work at leading order in $\alpha_s$. We get…