Organizers: Susan Gardner gardner@pa.uky.edu Barry Holstein holstein@physics.umass.edu Jeffrey Nico jnico@nist.gov W. Michael Snow wsnow@indiana.edu Program Coordinator: Laura Lee lee@phys.washington.edu (206) 6853509
Tentative Program Schedule, with WeekbyWeek Foci Electric Dipole Moments and CP Violation Workshop Application form Exit report

March 19  June 8, 2007
The growth of neutron physics facilities worldwide yield unprecedented opportunities to study the neutron's fundamental nature. Our program plans not only to support experiments planned at incipient facilities, such as at the Spallation Neutron Source (SNS), but also to nuture new experimental and theoretical directions.
Fundamental neutron physics is naturally
of broad compass, with questions which span subfield boundaries.
We wish to bring together theorists and experimentalists
to consider and ultimately to solve problems in
topics such as we describe.
Breaking of Discrete Symmetries The violation of symmetries such as P, CP, and T can be studied in a variety of lowenergy processes. Hadronic parity violation can be probed through the study of the parityviolating asymmetry in np→dg and through neutron spin rotation experiments. Essential questions include what fundamental parameters can be extracted, and how such can be rationalized from a rigorous nonperturbative formulation of QCD. The empirical bound of the neutron electric dipole moment (EDM) constrains extensions of the Standard Model (SM) with additional sources of CP violation and is relevant to the investigation of the cosmological problem of the baryon asymmetry of the universe. We hope to realize a synergy of theorists of greatly varying expertise, including those expert in fewnucleon and nuclearstructure physics, in effectivefieldtheory techniques, in nonperturbative methods and models of QCD, as well as those versed in building extensions of the SM, to realize fruitful studies of P, CP, and T violation in hadronic systems at low energies.CKM Unitarity and New Interactions at the Weak Scale The focus of the neutron lifetime and neutron bdecay asymmetry experiments is the elucidation of the CKM matrix element V_{ud}, to realize, with V_{us} and V_{ub}, the world's best test of the unitarity of the CKM matrix. The significance of this empirical test is a crucial constraint on grand unified theories which admit "new" physics at the TeV scale. This is, in turn, shaped by the surety of the "inner" radiative correction calculation which enters the determination of V_{ud} from the empirical vector coupling constant g_{V}. We hope to foster discussion of how effective field theory techniques employed in the study of K_{l3} decay may be extended to baryonic systems, to modernize and possibly improve upon earlier work. Detailed measurements of the decay correlation coefficients can also be used to limit the presence of nonVA weak interactions and thus bound the presence of new weakscale physics. Exploring the manner in which these tests complement precision electroweak data is of great importance.Gravity and New LongRange Interactions Two disparate experiments suggest that known quantum mechanical principles apply to gravitational potentials as well. The first is a measurement of the gravitational phase shift in neutron interferometry; the second is the recent inference of gravitational bound states of ultracold neutrons (UCN). The UCN results can be used to bound new longrange interactions, which occur naturally in models with "extra" dimensions, at the nanometer scale. Such experiments potentially offer an interesting complement to experiments of greater sensitivity at larger distance scales. Understanding the role neutron experiments can play in shaping our understanding of gravity in the quantum regime is a topic we would like to explore.Neutron Structure and Interactions At low energies, the neutron's structure is probed primarily through the ne scattering length, which yields the rms charge radius of the neutron, and electric and magnetic polarizability measurements. Theoretical predictions of the neutron charge radius, be it from lattice QCD, or from the analysis of precision atomic and electron scattering data on the proton and deuteron, would be welcome. The precision of lowenergy n scattering experiments to yield scattering lengths and polarization observables have improved greatly; here interest revolves around their theoretical interpretation to yield insight into the NN interaction.Nuclear Astrophysics The measured neutron lifetime is crucial to the predictions of bigbang nucleosynthesis (BBN) and ultimately to understanding the manner in which the universe has evolved throughout its history. Here, too, effectivefieldtheory techniques play a role in realizing precision predictions of key reaction rates, such as np→dg. It would be useful to develop a perspective on the experimental and theoretical work yet needed to sharpen the comparison with data as much as possible. Agreement of the predictions of BBN with observed element abundances can constrain the parameters of various SM extensions as well. Spallation neutrons can also be used to generate neutrinos and thus to study the physics of neutrino oscillations. 