Strange Form Factors, Direct CP Violation, and a Low Energy Standard Model Test

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

The research proposed here seeks the answer to two fundamental questions about matter. The first is what role does the sea of strange quark-antiquark pairs in the nucleon play in the determination of its electromagnetic properties? We are participating in the G0 experiment at Thomas Jefferson National Accelerator Facility to address this issue. The experiment will measure the parity-violating asymmetry in the scattering of polarized electrons from the proton and deuteron over a wide range of momentum transfers; this will allow for the strange electric and magnetic form factors to be separately extracted. This experiment will be in a commissioning and data-taking phase during this grant period. The second question is whether or not there is any new physics beyond the Standard Model of electroweak physics. This question will be addressed by the QWEAK experiment at TJNAF, which will measure the proton's neutral weak charge via parity-violating electon scattering at very low momentum transfer. This proton's weak charge has a well-defined prediction in the Standard Model; a precise measurement of it is sensitive to many poplular scenarios for extending the Standard Model. This experiment will be in a construction phase during this grant period.