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Abstract:
Neutrinos in the early Universe decoupled essentially in helicity eigenstates. As they propagate through the Universe, their helicities could be modified via two effects. First, neutrinos with a finite magnetic moment would rotate their spins with respect to their momenta as they encounter cosmic magnetic fields, modifying their helicities. Second, the bending of neutrino's spin by a gravitational field lags the bending of its momentum, again modifying its helicity. We calculate both effects and investigate the implications of the helicity modification on the detection of relic neutrinos using the Inverse Tritium Beta Decay (ITBD) reaction. We find that the ITBD rate depends sensitively on the neutrino mass hierarchy and on the Dirac or Majorana nature of the neutrinos. This talk is based on three recent papers in collaboration with Gordon Baym.
Jen-Chieh Peng received his B.S. in physics from Tunghai University and his Ph.D. in physics from University of Pittsburgh. Following a postdoctoral research period at Saclay, France, he moved to Los Alamos National Laboratory in 1978, becoming a Laboratory Fellow in 1996. Peng joined the faculty at University of Illinois at Urbana-Champaign as Professor of Physics in 2002.
His research interests include the quark and antiquark structure of nucleons and nuclei, fundamental symmetries, and neutrino physics. Peng has conducted experiments at the AGS, LAMPF, Jefferson Laboratory, Fermilab, and CERN. He has carried out a series of experiments at Fermilab
to probe the antiquark content of the proton and nuclei using the Drell-Yan process. He is a spokesperson or co-spokesperson of some 10 nuclear and particle physics experiments, and a coauthor of over 430 journal articles. He has served on the Program Advisory Committees of Jefferson Laboratory, Brookhaven National Laboratory, and the Japanese hadron facility (J-PARC).
Biography:
Jen-Chieh Peng received his B.S. in physics from Tunghai University and his Ph.D. in physics from University of Pittsburgh. Following a postdoctoral research period at Saclay, France, he moved to Los Alamos National Laboratory in 1978, becoming a Laboratory Fellow in 1996. Peng joined the faculty at University of Illinois at Urbana-Champaign as Professor of Physics in 2002.
His research interests include the quark and antiquark structure of nucleons and nuclei, fundamental symmetries, and neutrino physics. Peng has conducted experiments at the AGS, LAMPF, Jefferson Laboratory, Fermilab, and CERN. He has carried out a series of experiments at Fermilab
to probe the antiquark content of the proton and nuclei using the Drell-Yan process. He is a spokesperson or co-spokesperson of some 10 nuclear and particle physics experiments, and a coauthor of over 430 journal articles. He has served on the Program Advisory Committees of Jefferson Laboratory, Brookhaven National Laboratory, and the Japanese hadron facility (J-PARC).
Peng was elected an Academician of the Academia Sinica in 2022, and he is the winner of the 2023 Tom Bonner Prize in Nuclear Physics of the American Physical Society.