Precision Measurement of the Parity-Violating Asymmetryin e-2H Deep Inelastic Scattering

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

This project will measure the parity-violating asymmetry in electron-deuterium deep inelastic scattering (PV-DIS) using the 6 GeV electron beam at the Thomas Jefferson National Accelerator Facility (JLab). The parity symmetry of nature is a fundamental property of the electromagnetic and strong interactions but was found to be violated in weak interactions in 1957. Since then, the phenomenon of parity violation has been widely used to study both the Standard Model of electro-weak interactions and the nucleon structure. Most parity violating scattering experiments so far, however, were carried out in the elastic scattering regime where the nucleon reacts as a rigid body. A remarkable feature of deep inelastic scattering is that in this regime the nucleon breaks down to its fundamental constituents -- quarks and gluons -- thus different aspects of electroweak interaction or nucleon structure can be revealed. More specifically, our goal is to extract the coupling coefficients C2q, which measures the product of the strengths of the electro-weak interactions between an electron and the Z0 boson and that between a quark and the Z0, and improve its precision to eight times better than the current published value. Such result would shed light on possible new physics beyond the current electroweak Standard Model and is complementary to other low and medium-energy Standard Model test experiments. In the near future, the PVDIS measurement will be extended after the JLab upgrade and a broad range of topics on electro-weak physics and the nucleon structure, including a potential new discovery by directly observing the charge-symmetry violation at the quark level, will be explored. The PI is playing a leading role in this project as a spokesperson. She is leading the effort to construct a new data acquisition system required for the experiment. This hardware development will provide valuable training and research experience for summer undergraduate and graduate students. This experiment will become the Ph.D. project for at least one graduate student from UVa. In the long term, the 6 GeV measurement forms the basis for the PI to develop a larger-scale (possibly international) collaboration to carry out extension of this program at the 12 GeV energy upgraded JLab.