Nonperturbative QCD calculations of hadronic matrix elements are needed to understand the structure of the matter in our universe and to search for physics beyond the Standard Model. Numerical lattice gauge theory is uniquely suited for this task and has reached a remarkable level of precision. Traditionally, lattice QCD determinations of hadronic matrix elements were restricted to situations with at most one stable hadron in the initial and final states, and with a single insertion of a local current. However, recent years have seen significant progress in calculating more complicated observables:

- Rigorous methods have been developed to study interacting two-hadron states in a finite lattice volume, and to relate two-hadron matrix elements computed in a finite volume to the physical infinite-volume matrix elements. These techniques have been applied to investigate resonances and to compute the nonleptonic weak decay K➙π π from first principles. Work is underway to study more complicated cases, including 2➙2 transitions, systems with more than two hadrons, inelastic scattering, and baryonic processes.
- The lattice QCD community is beginning to address nonlocal matrix elements contributing to flavor-changing processes. Recently, a first calculation of the long-distance contribution to the KL-KS mass difference was performed. There are efforts to compute long-distance contributions to flavor-changing neutral-current decays. Lattice calculations of leptonic and semileptonic decays, which are used to determine CKM matrix elements, have reached a level of precision where electromagnetic corrections need to be included; this may also require the evaluation of nonlocal hadronic matrix elements.
- Significant progress has been made recently in understanding the properties of nuclei from first principles using lattice QCD. Following lattice calculations of the binding energies, work is now underway to compute matrix elements describing the structure and interactions of these systems.

This workshop will bring together people interested in various aspects of the above topics, allowing the exchange of the latest ideas in this exciting and rapidly developing field.

Presentations will be mainly by invitation. We expect to be able to accommodate a **limited number** of contributed talks.

If you are interested in presenting a contributed talk, please contact one of the organizers.

- Stefan Meinel (U of AZ & RBRC) - Chair
- Taku Izubuchi (BNL & RBRC)

Click on the "Workshop Information" tab above to find accommodation information.