## New Theoretical Tools for Nucleon Resonance
Analysis

#### Argonne National Laboratory
Theory Institute

December, 2004 -- September, 2005

#### Coordinators:

Arne Höll, hoell@phy.anl.gov,
Harry Lee, lee@phy.anl.gov,

Craig Roberts, cdroberts@anl.gov,
Stewart Wright, svwright@anl.gov,

Physics Division, Argonne National
Laboratory
This programme is funded by the
Argonne Theory Institute

**Focus:**

It has long been recognized that a veracious description of nucleon
resonances (N*) is one of the most important requirements in the development
of a fundamental understanding of strong interactions. Indeed, the 2004
Office of Science Strategic Plan for Nuclear Science states that connecting
the observed properties of baryons with the underlying theoretical framework
provided by quantum chromodynamics (QCD) is one of the central challenges of
modern science. We must determine the manner in which the structure of N*
can emerge from QCD, the fundamental theory of strong interactions. A key
step along the way is the development of an understanding of the models of
hadron physics and the fidelity of their predictions.

Two puzzles in particular stand out: the so-called *missing resonance
problem*, which refers to the fact that numerous N* states predicted by
the SU(6)xO(3) constituent-quark model are not seen in pi-N scattering; and
the problem of the *interpretation of nucleon resonance parameters*,
which addresses the issue of just how can one relate QCD calculations of
hadron properties to the parameters extracted in amplitude analyses?

Motivated by these considerations, the Theory Group will host a programme
that will focus on the development of reaction theory for the electromagnetic
production of mesons with a particular emphasis on bridging the gap between
observation and QCD.

#### __Workshop 1: 2-6/May/05__

##### Objective:

- To understand the 'details' of each theoretical model and the the
numerical methods used in actual computations.
- Compare the theoretical input (coupling constants, form factors
etc.) to the calculations and the resulting scattering
amplitudes.
- Lay out a plan for exchanging information and/or developing
collaborations as a step toward a concrete plan for tackling the
CLAS data. In addition, this will advance planning for the
general workshop in August/September.

More details and a programme are available on the workshop webpage.

#### __Workshop 2: 29/Aug. - 2/Sept/05__

A participant list is available on the workshop webpage. Further information
will be added when it becomes available.