Fundamental Spin Physics

Fundamental Spin Physics Application/Institution: University of Kentucky Research Foundation Street Address/City/State/ZIP: 500 South Limestone, 109 Kinkead Hall, Lexington, KY 40526-0001 Postal Address: 109 Kinkead Hall, Lexington, KY 40506-0057 PI and co-PI names, telephone numbers, email addresses: • Wolfgang Korsch (PI), (859) 257-4083, [email protected] • Bradley Plaster (co-PI), (859) 257-3960, [email protected] Funding Opportunity Announcement Number: DE-FOA-0003201 DOE Office Sponsoring this FOA: DOE EPSCoR DOE EPSCoR Scientific/Technical Contact: Dr. Tim Fitzsimmons DOE Program–Topical research area: Nuclear Physics DOE Program Office Scientific/Technical Contact: • Dr. Spyridon Margetis (Medium Energy), Dr. Gulshan Rai (Medium Energy) • Dr. Paul Sorensen (Fundamental Symmetries) National Laboratory(s) participating: Argonne National Lab National Laboratory personnel participating in the proposed research: • Dr. Michael Bishof, Assistant Physicist, Fundamental Symmetries group in the Physics Division • Dr. Zein-Eddine Meziani, Argonne Distinguished Fellow and Group Leader of Medium Energy Physics in the Physics Division • Dr. Peter Mu¨ller, Principal Physicist, Deputy Group Leader, Fundamental Symmetries group in the Physics Division • Dr. Chao Peng, Assistant Physicist, Medium Energy Physics group in the Physics Division 1 We propose a research program related to two of the most fundamental problems in nuclear physics. i) What are the fundamental interactions and structures of matter? ii) What are the reasons for a matter- antimatter asymmetry of the Universe? We will use the world-class research environment at Argonne Na- tional Lab (ANL) to search for answers to these questions. To address the issue of the fundamental structure of matter, we plan to develop a new source of polarized 6,7Li-ions for the Electron-Ion Collider (EIC). Such a source will be a new and unique addition to the EIC physics program. It will allow us to open a completely new research direction in electro-nuclear physics. For example, we will be able to study the polarized EMC effect in ions beyond polarized deuterium or helium-3. The possible modification of the spin-structure of bound deuterons, noting that lithium-6 is predominantly an α-d bound state, can be investigated as well. In a second project, we will search for the permanent electric dipole moment (EDM) of the 225Ra atom with unprecedented precision. Since ANL expects to have access to a new source of radium-225 in the near future and given the already existing infrastructure in the laboratory, this is an ideal time to restart the Ra-EDM experiment and strengthen the UK-ANL collaboration. Both projects will open new opportunities for UK undergraduate and graduate students and expose them to a research infrastructure that is not accessible at the University of Kentucky. The students will gain significant expertise in accelerator physics, real-time signal processing, lasers, and atomic traps, to name a few. The program described in this proposal overlaps perfectly with the recommendations and goals outlined in the recently released Long Range Plan of Nuclear Physics. Development of a Nuclear Spin-Polarized 6,7Li Ion Source for the EIC The EIC will be the next medium- to high-energy collider in the US. The physics goal of this collider is to study the quark-gluon structure of nucleons and light ions with unprecedented precision. This physics is sometimes termed ”femtoscopy” since it probes the properties and strong interactions of Nature’s most fundamental building blocks, the quarks and gluons, at distances less than the radius of the proton. A significant research component of the EIC will be to study the dynamics that drive the emergence of the spin of the nucleons and how the spin structure is modified when the nucleons reside inside a nucleus in a kinematic regime that is inaccessible anywhere else. For this purpose, polarized electrons will be scattered off polarized protons, deuterons, and helium- 3. We propose to add polarized 6,7Li to this list. If successful, a lithium program will allow us to access tensor spin observables, which only occur in systems with nuclear spins ≥ 1?. A comparison of deuteron and lithium-6 ion spin observables will yield new insight into the nuclear spin structure of more complex systems. Korsch and several scientists from ANL started the development of a polarized lithium source during Korsch’s sabbatical stay at ANL. A test stand is already operational, and the first atomic 7Li beams have been produced and profiled using surface ionization on thin rhenium ribbons. Dr. Chao and Dr. Meziani are spearheading this effort at ANL. Korsch has previously worked on polarized 6,7Li ion sources at the Max Planck Institute in 2 Heidelberg, so he can add significant expertise to the whole project. This EPSCoR grant would allow us to send UK students to ANL for extended periods and give them access to a high-quality research environment. Search for a Permanent Electric Dipole Moment in 225Ra The search for permanent electric dipole moments (EDMs) has gained significant traction during the last decade. Although the Standard Model of particle physics is highly successful in describing Nature’s most fundamental structure and interactions, many unanswered questions remain. For example, about 95% of the matter/energy budget in the Universe is composed of invisible dark matter and dark energy; what is the origin and hierarchy of mass, and why is there such a large matter-antimatter asymmetry in the Universe? These questions are the main focus of modern atomic, nuclear, and particle physics research. One possible way to explain the matter-antimatter asymmetry is the existence of “large” permanent electric dipole moments in fundamental fermions, nucleons, nuclei, or atoms. Among all these possibilities, 225Ra is an especially promising candidate due to a large octupole deformation, a closely spaced parity doublet, and its relativistic atomic structure. About 15 years ago, ANL initiated an effort to search for an 225Ra EDM using modern AMO technologies such as laser cooling and atom trapping. Korsch and one of his graduate students were part of this experimental effort. The first impressive limit was extracted and published. Unfortunately, the endeavor had to be paused for several years since all available 225Ra isotopes were used for medical radiation therapy. However, owing to a recent development in the usage of thorium-229 (note: 225Ra is produced by α decay of 229Th), large amounts of 225Ra have become available for research again, and the EDM experiment at ANL will continue its efforts to improve the current limit on the 225Ra EDM by several orders of magnitude. One of the dominating uncertainties in the current limit is associated with the knowledge of the stability and uniformity of the magnetic field. The previous experiments were performed without the implementation of an optimized comagnetometer. The magnetic field stability was determined to be ?B=(−0.3±0.5) pT resulting in one of the the most dominant systematic uncertainties. To reduce E-field-correlated changes in the B-field significantly, a new ultra-low-noise current source and a sensitive optical comagnetometer must be developed. These components should allow us to monitor and maintain a constant, low-noise, gradient-free magnetic field for several months. Plaster and Korsch have crucial experience in monitoring and stabilizing magnetic fields due to their involvement in previous and ongoing EDM experiments. Plaster is responsible for magnetic field monitoring in the LANL and SNS neutron EDM searches, and Korsch helped develop a field monitoring system for the original 225Ra EDM experiment. Drs. Bischof and Mu¨ller are leading these efforts at ANL. In summary, we plan to participate and take responsibility for two significant experiments related to nu- clear spin physics at ANL. The proposed projects will provide new opportunities for UK students to contribute substantially to high-profile science and boost key DOE research efforts. The collaboration will commit to paying special attention to the inclusion of minorities and to promoting an equitable research environment. 3