This research program is centered on experiments addressing fundamental issues of nuclear physics. An experiment is being designed to search for the neutron electric dipole moment, an observable that violates the reversal of time and plays an important role in descriptions of elementary particle physics and on the observed asymmetry of matter and anti-matter in the universe. Another experiment will measure second order effects in electron-proton scattering to address a present puzzle on the proton structure data. And there are on-going experiments with cold neutrons measuring neutron decay parameters and the strength of the weak interaction among quarks.
The activities will produce new scientists at the Ph.D. level, will give research experience in fundamental physics to undergraduate students, and will contribute to the ascent of a large state university as a premier research institution. The advancement of the careers of women and ethnic minorities is an integral part of this process. Furthermore, the demand for state-of-the-art equipment utilizes the ASU's technical workforce and that of the society at large.
The major goals of the project are the design, construction, execution, and analysis of nuclear physics experiments and the training of graduate students together with the education of undergraduate students. During the life of the award our group worked in the execution and preparation of nuclear physics experiments with polarized cold neutrons and electron scattering. The NPDGamma experiment at the Spallation Neutron Source (SNS) measures the parity-violating (PV) photon asymmetry in the capture of polarized cold neutrons by protons. This PV asymmetry is unambiguously related to the strength of the hadronic weak interaction due to pion exchange. The experiment finished data taking in the first half of 2014. Our graduate student (D. Blyth) was stationed in Oak Ridge, TN and maintained the DAQ system and began one of the final parallel analyses of the PV photon asymmetry. Previously, during the commissioning phase in 2012 we measured PV asymmetries in Al and Cl nuclei and led to our graduate student (S. Balascuta) to obtain his Ph.D. the same year. During the award we completed the RDK experiment at NIST: a precision measurement of the radiative decay of the free neutron with the goal of improving the precision of quantities associated with the decay of the free neutron. Withi this work our graduate student (B. O'Neill) obtained his Ph.D. in December, 2012. The Nab experiment at the SNS consists of precise measurements of neutron beta decay parameters using a novel field-expansion spectrometer coupled with state-of-the-art silicon detectors. The spectrometer is under construction through an MRI proposal. Our group is responsible for the design and construction of the magnetic passive shielding needed to fulfill the facility’s stringent magnetic field environment. We have concluded the magnetic design and carried out a preliminary structural analysis. The nEDM experiment at the SNS (planned to follow the Nab experiment) is a search for the neutron electric dipole moment. The goal is to measure or set a stringent new upper limit on the electric dipole moment of the neutron which is a time-reversal-violating observable that plays an important role in descriptions of elementary particle physics, on the understanding of the general pattern of T- (CP-) violation and possibly the cause of the observed asymmetry of matter and anti-matter in the universe. Graduate student Adam Dipert actively worked on the R&D phase through the PULSTAR activities at the NCSU reactor and will be writing his Ph.D. thesis on the measurements planned there with ultracold neutrons. The OLYMPUS experiment at the DORIS ring in DESY, Hamburg completed its data taking in 2013. The measurements consist of electron and positron elastic scattering from hydrogen to determine the contribution of multiple-photon exchange in elastic lepton-nucleon scattering and address the present puzzle of the proton form factor ratio. Graduate student Lauren Ice has worked on many key aspects of OLYMPUS since 2010, and she is now working on the analysis of the data as part of her Ph.D. thesis. A new experiment with electron scattering was conceived during the life of the award. The experiment, DarkLight, searches for dark photons in the 10-100 MeV mass range as a way to elucidate the origin of the forces of dark matter. Phase I of the experiment was funded through an MRI grant, which our group is part of.
