Organizers:
Haiyan Gao
Walter Glöckle
Alan Nathan
Daniel Phillips
Program Coordinator:

June 1620, 2008
At the same time, exciting theoretical developments involving effective field theories (EFTs) are providing new insights into the reactions measured at these machines. This is possible because EFT's character as a systematic expansion in ratios of physical scales provides a means to progressively improve the treatment of both nuclear forces and the currents through which nuclear degrees of freedom interact with photons. Two EFTs are relevant for the energy domain covered by these facilities. At lower energies the socalled "pionless" EFT is applicable. Once the energy is high enough that pionic degrees of freedom are specifically probed, chiral EFTs can be used to describe the interaction of nuclei with photons. In both cases, EFT's description of nuclear structure and reactions involves progressively smaller effects in the nuclear force, e.g. two and threepion exchange and consistent threenucleon forces. In particular, the chiral EFT forces have now been worked out to several orders in the expansion. Further improvement in this description can be expected too, as new three and fournucleon forces at higher orders in the expansion are currently under development. While much is known about the electromagnetic properties of the nucleon itself in these chiral EFTs, work on building up the current operators for light nuclei is at a relatively early stage. But such calculations hold the promise of operators for electromagnetic reactions that are derived using techniques analogous to those employed for the nuclear force, and describe data at a concomitant level of accuracy. Furthermore, for A ≤ 4 modern nuclear Hamiltonians can now be solved essentially exactly for observables involving both bound and scattering states using, e.g. FaddeevYakubovsky or Correlated Hyperspherical Harmonics techniques. These theoretical advances give us access to theoretical descriptions of reactions on light nuclei which are systematically improvable, and whose consequences can be reliably computed. Used in concert with accurate experiments, such calculations provide a powerful tool to elucidate critical details of the strong nuclear force. The combination of theoretical and experimental advances will facilitate examination of three exciting areas: (1) Examination of threebody forces through photoinduced processes on 3He, (2) Lowenergy photodisintegration of light nuclei and (3) Compton scattering in systems with A=1, 2, and 3. This workshop will bring together leading theorists involved in calculations in these areas and experimentalists doing experiments at some of the aforementioned photon facilities. The goal of the workshop will be to identify the most promising experiments for access to these three physics goals. This will include detailed collaborative work and discussions between theorists and experimentalists on which particular experiments and kinematics/observables are optimal with respect to both theoretical control and experimental viability. 