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G. M. Prosperi

Publications and source records attributed to G. M. Prosperi.

26 records · Page 2Linked to original sources
arXiv1995

Quark--Antiquark Bethe--Salpeter Equation in QCD

We review our recent results \cite{bsult} on the derivation of a B-S equation in QCD in a Wilson loop context. We work in a second order formalism, use the Feynman--Schwinger path integral representation for a quark in external field and obtain a similar expression for a quark--antiquark amplitude in which the gauge fields appears only through the Wilson loop integral $W$. A $ q \bar{q}$ B-S equation is obtained starting from this expression under the assumption, already used in the derivation of heavy quark potential, that $i \ln W$ can be expressed as the sum of a perturbative contribution and an area term. The intrinsically nonperturbative derivation method is first discussed on the simpler case of two spinless particles interacting through a scalar field. The $q \bar{q}$ semirelativistic potential is reobtained in the large quark mass limit.

hep-ph↗
arXiv1995

Three-body relativistic flux tube model from QCD Wilson-loop approach

First we review the derivation of the relativistic flux tube model for a quark-antiquark system from Wilson area law as we have given in a preceding paper. Then we extend the method to the three-quark case and obtain a Lagrangian corresponding to a star flux tube configuration. A Hamiltonian can be explicitly constructed as an expansion in $1 / m^2$ or in the string tension $σ$. In the first case it reproduces the Wilson loop three-quark semirelativistic potential; in the second one, very complicated in general, but it reproduces known string models for slowly rotating quarks.

hep-ph↗
arXiv1995

Confining Bethe--Salpeter equation in QCD

We derive a confining $ q \bar{q}$ Bethe--Salpeter equation starting from the same assumptions on the Wilson loop integral already adopted in the derivation of a semirelativistic heavy quark potential. We show that, by standard approximations, an effective meson squared mass operator can be obtained from our BS kernel and that, from this, by ${1\over m^2}$ expansion, the corresponding Wilson loop potential is recovered, spin--dependent and velocity--dependent terms included. We also show, that, on the contrary, neglecting spin--dependent terms, relativistic flux tube model is reproduced.

hep-ph↗
arXiv1995

Bethe--Salpeter equation in QCD

We extend to regular QCD the derivation of a confining $ q \bar{q}$ Bethe--Salpeter equation previously given for the simplest model of scalar QCD in which quarks are treated as spinless particles. We start from the same assumptions on the Wilson loop integral already adopted in the derivation of a semirelativistic heavy quark potential. We show that, by standard approximations, an effective meson squared mass operator can be obtained from our BS kernel and that, from this, by ${1\over m^2}$ expansion the corresponding Wilson loop potential can be reobtained, spin--dependent and velocity--dependent terms included. We also show that, on the contrary, neglecting spin--dependent terms, relativistic flux tube model is reproduced.

hep-ph↗
arXiv1995

Confining Bethe--Salpeter equation from scalar QCD

We give a nonperturbative derivation of the Bethe--Salpeter equation based on the Feynman--Schwinger path integral representation of the one--particle propagator in an external field. We apply the method to the quark--antiquark system in scalar QCD and obtain a confining BS equation assuming the Wilson area law in the straight line approximation. The result is strictly related to the relativistic flux tube model and to the $q \bar{q}$ semirelativistic potential.

hep-ph↗
arXiv1994

Wilson loops, $q \bar{q}$ and $3 q$ potentials, Bethe--Salpeter equation

The derivation of the $ q \bar q $ and the $ 3q $ potential for two dynamical quarks in a Wilson--loop context is reviewed. Some improvements are introduced. Only the usual assumptions in the evaluation of the Wilson loop integrals and expansions in the quark velocities are required for the result. It is shown that under the same assumptions it is possible to obtain the relativistic flux--tube lagrangian and a $ q \bar{q}$ Bethe--Salpeter equation with a confining kernel for spinless quarks. IFUM 482/FT

hep-th↗
arXiv1994

A consistent derivation of the quark--antiquark and three quark potentials in a Wilson loop context

In this paper we give a new derivation of the quark-antiquark potential in the Wilson loop context. This makes more explicit the approximations involved and enables an immediate extension to the three-quark case. In the $q\overline{q}$ case we find the same semirelativistic potential obtained in preceding papers but for a question of ordering. In the $3q$ case we find a spin dependent potential identical to that already derived in the literature from the ad hoc and non correct assumption of scalar confinement. Furthermore we obtain the correct form of the spin independent potential up to the $1/m^2$ order.

hep-th↗