We calculate the effective vertices for the quark-antiquark and the quark-antiquarkgluon production in the virtual photon Reggeized gluon interaction. The last vertex is considered at the Born level; for the first one the one-loop corrections are obtained. These vertices have a number of applications; in particular, they are necessary for calculation of the virtual photon impact factor in the n...

We study the quark-antiquark-gluon techniques in SU(3) lattice QCD, for different geometries, namely angles of 0, 45, 60, 90, 120, 135 and 180 degrees, between the quark-gluon and the antiquark-gluon segments. We calculate the form of the static potential and discuss whether, or not, two-body interactions exist between the three different bodies. We also study the existence of repulsion between...

We study the quark-antiquark-gluon techniques in SU(3) lattice QCD, for different geometries, namely angles of 0, 45, 60, 90, 120, 135 and 180 degrees, between the quark-gluon and the antiquark-gluon segments. We calculate the form of the static potential and discuss whether, or not, two-body interactions exist between the three different bodies. We also study the existence of repulsion between...

We study the quark-antiquark-gluon techniques in SU(3) lattice QCD, for different geometries, namely angles of 0, 45, 60, 90, 120, 135 and 180 degrees, between the quark-gluon and the antiquark-gluon segments. We calculate the form of the static potential and discuss whether, or not, two-body interactions exist between the three different bodies. We also study the existence of repulsion between...

In this review I cover recent developments concerning the construction of non-relativistic effective theories for perturbative heavy quark-antiquark systems and heavy quark mass definitions. I then discuss next-to-next-to-leading order results on quarkonium masses and decay, top quark pair production near threshold and QCD sum rules for Υ mesons. (November 1999, CERN-TH/99-355, hep-ph/9911490) ...

We present a theoretical framework that accounts for the new DJ and DsJ mesons measured in the open-charm sector. These resonances are properly described if considered as a mixture of conventional P−wave quark-antiquark states and four-quark components. The narrowest states are basically P−wave quark-antiquark mesons, while the dominantly four-quark states are shifted above the corresponding tw...

We consider heavy quark and antiquark off-shell spinorial currents with emission of an arbitrary number of gluons of positive helicity. From this results we calculate the corresponding on-shell scattering amplitude and the quark-antiquark vector current. Then, we show that in the heavy top quark effective theory the holomorfic component of the Higgs → qq̄ + n-gluon amplitude vanish for helicity ...

We study the mixing of excited states of a Hydrogen atom in a cavity with de-excited states plus a confined photon as a model for the coupling of quark-antiquark and quark-antiquark-gluon hybrid states in QCD. For an interesting range of parameters, the results are analytic. We find a case for which wavefunctions (and hence decay patterns) may be at odds with mass with respect to identification...