NPA Seminar: Krishna Kumar, Stony Brook University, “Electrons are not Ambidextrous: New Insights from a Subatomic Matter of Fact”

Thursday Mar 5, 2015, 3:30 PM → 4:30 PM US/Eastern

WLC 108

Fixed target experiments at accelerators have been used since the dawn of modern physics to study the structure of matter. The most precise and detailed information on fundamental forces and the size and shapes of atomic nuclei and their constituents have come from electron scattering experiments. Over the past forty years, significant new discoveries about subatomic matter have been made by employing longitudinally polarized electron beams. There is a tiny difference (of order parts per million) between the probabilities for scattering left- and right-handed electrons off subatomic matter (this constitutes a failure of parity symmetry), which can be used to gain unique new insights into neutron distributions in nuclei, the nature of constituent quarks and sea quarks in nucleons, and to search for new interactions that might have shaped the evolution of the early universe. I will describe the experimental technique to measure the tiny left-right parity-violating asymmetries in electron scattering, report on the nuclear and particle physics implications of recent measurements, and motivate the need for new and more precise experiments.