Fundamental Studies in Nuclear Physics

Precision measurements in nuclear physics have important implications across an enormous range of length scales: from the fundamental forces between the smallest particles to the behavior of the largest stars. Undergraduate and graduate students, working with the PI, will perform precision measurements of the lifetime of the free neutron which can be compared with detailed calculations to search for the influence of new, undiscovered heavy particles that modify the fundamental forces. Using very slow trapped free neutrons, known as ultracold neutrons, The PI and his group will make measurements of the number of neutrons in the trap as a function of time to provide a precision measurement of the neutron’s lifetime. This group will also perform a separate measurement of the probability that carbon and helium nuclei fuse to produce an oxygen nucleus in the interior of very massive stars. This probability directly affects which of these stars can collapse into a black hole. Thus, improved understanding of this probability and its impact on massive black hole production can be compared with the observed distribution of black holes measured via gravity wave observations. Given the large size of the data sets and the complexity of the analysis, Artificial Intelligence and Machine Learning (ML) will play an important role in providing an efficient and careful analysis of the data. Our previous work in analyzing neutron decay utilized Principal Component Analysis (a widely used technique in ML) to minimize uncertainties. These projects also involve quantum control of neutron spins, the technology of quantum sensors and the operation of cryogenic superconducting magnets. Participation in these experiments by undergraduate and graduate students helps provide the nation with a highly trained workforce in Nuclear Science and Technology, with applications in medicine, new technology, national defense as well as basic science. A precise value of the neutron lifetime can be combined with other neutron beta-decay properties to provide a stringent test of the unitarity of the quark weak-mixing matrix. Its lifetime is also critical in predicting the primordial helium abundance in the Universe following big-bang nucleosynthesis. We are collaborators on an experiment which uses magnetic fields to trap ultracold neutrons, allowing them to be stored for varying lengths of time and then counted to determine the lifetime. This work will provide additional input that may also help resolve the so-called neutron lifetime puzzle wherein different lifetime measurement protocols (neutron beam vs bottle measurements) do not agree on the neutron’s lifetime. The 12C(α,γ)16O reaction plays an outsized role in nuclear astrophysics as it impacts the evolution and final state of low to medium mass stars, the abundances resulting from element production in such stars and the maximum mass of stellar formed black holes. Because of its wide-ranging impact, improving the uncertainty in the stellar reaction rate at helium burning temperatures remains a major milestone for the field. We propose to carry out a new experiment at Argonne National Laboratory’s ATLAS facility to significantly improve our understanding of the stellar reaction rate of this important reaction. This data can help reduce the uncertainty in the predicted distribution of stellar black holes following supernovae and allow comparisons with the distribution determined from observations of gravity waves from black hole-black hole mergers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2610065 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Bradley Filippone | Institution: California Institute of Technology, PASADENA, CA | Award Amount: $900,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2610065 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2610065.html