Vertex In QCD Research Articles

A relativistic quark model for hadrons

Relativistically covariant quantum mechanics with direct interaction is used to construct a model of several confined particles. Suggested by the three-gluon vertex of QCD this model is characterized by an interaction center and therefore called «the bola model». It is a phenomenological model with the aim of affording easy and reliable computations of meson and baryon mass spectra for given interactions. The presentation is preceded by a corresponding classical relativistic dynamics.

Solution of the renormalization group equation and ultraviolet asymptotics of gauge-dependent propagators in QCD

The general solution of the RGE for gluon vertices in massless QCD is obtained for arbitrary α. It is shown that, contrary to the view prevailing in the literature, the ultraviolet behaviour of gluon vertices is discontinuous both in the gauge-fixing parameter α and in the number of flavours.

Quarkonium decays: Testing the 3-gluon vertex

We study the 3-jet decays of S- and P-wave quarkonia with C=+. If observed, some of these will offer a way of seeing the 3G vertex of QCD via 1S 0, 3P 0, 3P 2(Q Q ) → GGG + Gq q → 3 jets. (As is well-known, cancellations reduce 3 P 1( Q Q )→ GGG.) We elaborate in detail the S-wave decay, as it is expected to show all the characteristic features of orthoquarkonium decays into 4 jets, 3S 1(Q Q ) → GGGG + GGq q → 4 jets, which we will comment upon. These quarkonium decays offer a very clear signal for QCD as a non-abelian local gauge field theory with color-charged gluons.

Two-loop anomalous dimensions of timelike cut vertices in QCD

Abstract The two-loop corrections to the anomalous dimensions of timelike cut vertices in QCD are presented for the non-singlet case. We check that cut vertices are renormalizable to two-loop order.

Higher Order Calculations of Cut Vertices in QCD

Higher Order Calculations of Cut Vertices in QCD

Space and time like cut vertices in QCD beyond the leading order - non-singlet sector

In the framework of the cut vertex formalism we present the results of calculations of the quantities needed for a next to leading logarithmic analysis of scaling violations for structure and fragmentation functions in Quantum Chromodynamics. We find that an analytic continuation relation holds, between the time and space like regions, while the Gribov-Lipatov reciprocity relation is violated.

Space- and time-like cut vertices in QCD beyond the leading order—The singlet sector

The analytic continuation relation found in the non-singlet structure of the processes e +h→e −X and e −e +→hX up to the next-to-the-leading-logarithm approximation, is shown to be true also for the singlet case. This relation is used to find the two-loop anomalous dimensions for the singlet time-like cut vertices from the anomalous dimension of the singlet space-like cut vertices. We give also the singlet time-like coefficient functions.

Slavnov-Taylor identities in Weinberg's renormalization scheme

Weinberg's renormalization scheme, although more cumbersome from the computational point of view, has a more immediate physical interpretation than 't Hooft's minimal renormalization scheme. It is expected to lead to smaller higher-order coefficients in a perturbative approach to QCD. However, it a priori violates the Slavnov-Taylor identities. A complete study of this problem is performed, both theoretically and for the practitioner's sake. The ambiguities in the choice of the tensorial basis of some of the QCD vertices, as well as the dependence in the gauge parameter are used for substantiating, eventually, the Slavnov-Taylor identities in this renormalization scheme.

The three-gluon vertex of QCD

We show how the Q 2 evolution of gluon jets can be used to provide indirect but strong evidence for the three-gluon vertex of QCD. We propose looking for this evolution in the Q Q ¯ → 3 G → hadrons decay of successive 1 3S 1 quarkonium states. The results apply to other processes if G-jets can be isolated.