The Helmut W. Baer Lecture is a special colloquium supported by family and friends in honor of Dr. Helmut Baer. Dr. Baer's career in physics began with his work at the University of Michigan where he was awarded a doctorate in nuclear physics in 1967. He published over 100 articles that cover a range of physics topics including nuclear physics and pion interactions. Dr. Baer was named a Fellow of the American Physical Society in March of 1989, and to his delight enjoyed countless opportunities over the years to talk about physics at universities and conferences internationally. Dr. Baer set the highest personal standards for himself and his research. This lecture is held approximately every two years.
The 2019 Helmut W. Baer Lecture in Physics
Dr. Chen-Yu Liu
Lecture Title: The Neutron Lifetime Puzzle
Abstract: Neutrons make up half of all matter but become unstable when freed from the nucleus. The precise value of the neutron lifetime plays an important role in nuclear and particle physics and cosmology. Professor Liu will describe the latest measurement, which traps neutrons by levitating neutrons with a large array of permanent magnets. The lifetime measured this way appears different than that measured with a beam of neutrons leading some to conjecture their disappearance into an undetectable state.
Chen-Yu Liu's research group focuses primarily on experimental tests of fundamental symmetries. Other than using high energy colliders to directly create new particles, they search for the footprints of exotic particles in low temperature, low energy systems. These searches look for the parity violating, CP violating, or time reverseal violating features in the systems of interest.
Currently, they concentrate on two areas of low-energy particle physics. The first is the development of ultra-cold neutron (UCN) sources for fundamental physics experiments, the other is a search for the electric dipole moment (EDM) of the electron in solid state system and EDM of the neutron.
UCN is a new tool available only in the past two decades. UCN can be trapped in material bottles or magnetic traps, and allows for precision measurements on various observables of neutrons. UCN has been applied to high precisioin measurements on the beta-decay lifetime, decay asymmetries, and the search for its intrinsic EDM. In light of these potentials, their group is developing the next generation of UCN source using the magnetic scattering in low temperature solid oxygen. They plan to build a university based UCN source coupled to the low energy neutron source (LENS) which is in operation at IUCF.
The search of EDM has a high discovery potential to shed lights into the sources of CP violation required to produce the matter-antimatter asymmetry of the universe. They are pursuing the search of EDM of electron using a solid-state system at sub-Kelvin temperatures. The experiment is designed to measure a Stark induced magnetization (through EDM interaction) using state-of-the-art SQUID magnetometry. A (cryogen-free) dilution refrigerator will be used to further enhance the sensitivity of EDM at low temperatures. They are also doing R&D for the SNS neutron EDM experiment, especially in the subsystem involving the SQUID magnetometers.
Previous lectures in this series:
2018: Dr. Kate Scholberg, Duke University
2016: Dr. Witold Nazarewicz, FRIB/NSCL (MSU)
2015: Dr. Hiroyuki Oigawa, Japan Atomic Energy Agency
2011: Professor David W. Hertzog, University of Washington
2008: Professor John P. Schiffer, Argonne National Laboratory and the University of Chicago
2006: Professor Arthur B. McDonald, Physics Department, Queen's University
2004: Dr. Steve Lamoreaux, Los Alamos National Laboratory