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New Theoretical Tools for Nucleon Resonance Analysis

Argonne National Laboratory Theory Institute
December, 2004 -- September, 2005


Arne Höll,, Harry Lee,,
Craig Roberts,, Stewart Wright,,
Physics Division, Argonne National Laboratory

This programme is funded by the Argonne Theory Institute

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

  1. To understand the 'details' of each theoretical model and the the numerical methods used in actual computations.
  2. Compare the theoretical input (coupling constants, form factors etc.) to the calculations and the resulting scattering amplitudes.
  3. 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.