Particle Physics Seminar
University of Massachussetts, Amherst, MA
April 27, 2001
Probing Meson Structure with Photons
presented by
Richard T. Jones
University of Connecticut
Abstract
The scalar mesons
f
(980) and
a
(985) are
two of the best-verified states in the excited meson spectrum. They appear
as narrow resonances in the 2
and
![](/symbols/pi.lc.gif)
mass spectra, respectively, as observed in hadroproduction reactions and
in the decays of heavier particles such as the
J/
and the
Z
.
Although they were once thought to be members of the fundamental nonet of
scalar qq' mesons, conventional wisdom is now inclined against that
assignment in favor of an exotic (i.e. non-qq') interpretation for these
states. These two models are quite different in terms of their charge and
current distributions, and so it was suggested early in the 90's (and
probably before that) that an experiment using the photon as a probe
might distinguish empirically between them. This idea has stimulated
a number of experimental searches for these decays by groups working at
e+e- colliders in Europe and at Jefferson Lab in the US. Results are
now emerging which seem to support a non-quark-model assignment. The
status of the analysis and issues surrounding the interpretation of
these data will be addressed.
OUTLINE
-
Physics motivation
-
Phenomenology of the scalar mesons
-
Theoretical models: how to build a molecule
-
Implications of Phi radiative decays
-
Radphi experiment at Jefferson Lab
-
Experiments at Phi factories
-
Present status and future plans
(pdf slides)
This material is based upon work supported by the National Science Foundation under Grant No. 0072416.
Richard Jones