M. R. Pennington

What can asymptotic freedom say about e+e− → hadrons?

Abstract We discuss the continuation of asymptotically free quark model predictions for e+e− → hadrons in the complex q2 plane from spacelike to near timelike regions. At currently available energies we find we must compute gluon corrections to both the real and imaginary parts of the hadronic vacuum polarization tensor. Using quark masses defined by the position of the pole in the quark propagator we find good fits to the smeared data for a variety of models. However, use of an “off pole” definition of quark masses leads to a breakdown of the perturbation expansion even in regions far away from the real axis. Fits to the data outside these regions give highly correlated results dependent on the value of the strong coupling constant and the masses of the heavy quarks or leptons present. For a choice of the strong coupling constant consistent with observed scale violations in electroproduction, we find the data favors five quark flavors with a fifth quark of “mass” 2.3 GeV and a heavy lepton of mass ⋍ 2 GeV.

Dynamical generation of scalar mesons

Starting with just one bare seed for each member of a scalar nonet, we investigate when it is possible to generate more than one hadronic state for each set of quantum numbers. In the framework of a simple model, we find that in the

Masses from nothing. A non-perturbative study of QED3

I=1

Perturbative QCD for timelike processes: What is the best expansion parameter?

sector it is possible to generate two physical states with the right features to be identified with the

Decay channels and charmonium mass shifts

{a}_{0}(980)

Is low energy γγ→π0π0 predictable?

and the

Gauge-independent chiral symmetry breaking in quenched QED.

{a}_{0}(1450).

Probing the structure of f0(980) through radiative φ decays

In the

Towards a model-independent determination of the φ → γf0 coupling

I=1/2

One-loop QED vertex in any covariant gauge: Its complete analytic form

sector, we can generate a number of physical states with masses higher than 1 GeV, including one with the right features to be associated with the