My research centers on the study of the structure of the nucleon, and in particular its intrinsic angular momentum, known as spin. The contribution of the quarks to the nucleon spin has been found to be surprisingly low, around 25%, in high energy lepton scattering experiments. At Jefferson Lab the energy of the electron beam is ideal for investigating the excited states of the nucleon, or resonances. Very little data exist on the spin structure of the nucleon in this energy regime. In Hall B, we scatter polarized electrons on polarized proton and deuteron targets and measure the asymmetry, which can be related to fundamental aspects of the nucleon spin. The deuteron, (a loosely bound proton and neutron pair with spin 1), can be used to extract information on the neutron by the using the results of the proton experiment.
We are also carrying these
experiments one step further and looking at the experimental asymmetry for pion
production from the nucleon. The
pion is the lightest meson (quark
anti-quark pair) and is often emitted in the decay of a nucleon resonance back
to its ground state. For example, the first excited state of the proton, the
delta, can be excited by electron
scattering and decay back into a proton plus neutral pion, or a neutron plus
positive pion. I am focusing on the
emission of a negative pion from the polarized deuteron target, which comes primarily from the decay of a
neutron resonance into a proton plus negative pion. In this way it is possible to study the spin structure of the
neutron resonances for the first time.
Curriculum Vitae (July 2017) Experimental
Nuclear Physics Group