Quantum chromodynamics (QCD) is the currently accepted theory of the strong nuclear force which binds quarks and gluons together to form hadrons, such as the proton and neutron. Understanding hadron formation is a long standing problem in nuclear/particle physics. A major objective of this proposal is to use large-scale computer simulations with QCD formulated on a space-time lattice to carry out ab initio determinations of the mass spectrum of hadrons expected from the QCD theory. The novel feature of the proposed activities is the use of large sets of spatially extended hadron operators in order to study more-massive excited hadron states, not just the lightest states. These states are currently of great interest to experimentalists, exemplified by the Hall B N-star program and the GlueX experimental program in the proposed Hall D at the Thomas Jefferson National Accelerator Facility, as well as the CLEO-c project at Cornell. Understanding the physics of quark confinement within hadrons is also an important intellectual challenge; in fact, the Yang-Mills mass gap is one of the seven so-called Millenium Prize problems announced by the Clay Mathematics Institute of Cambridge, Massachusetts. The proposed research incorporates the participation of two graduate students, and possibly one or more undergraduate students, whose educations will be enhanced not only by involvement in scientific projects at the forefront of nuclear theory, but also with high-technology training in the use of state-of-the-art parallel computing resources. Students will be funded to participate in international conferences. The broader impacts of the proposed activities will be strengthened through articles in popular publications and by posting results with simplified background information on publicly accessible web pages.
