My research focus is on fundamental questions in particle physics but the experiments often exploit precision techniques from atomic and nuclear physics. There are often implications for astrophysics and cosmology. Currently I interested in the pattern of neutrino masses and mixing and with colleagues we operate a massive neutrino detector in Kamioka, Japan. We are also building a one-ton cryogenic double beta decay detector in Gran Sasso, Italy.
Our group is based on campus and LBNL, involving postdoctoral fellows, LBNL staff and Berkeley students. A number of projects are underway but graduate students focus on a specific experiment as a thesis topic. Larger projects are done in collaboration with other groups. Ph.D. students are expected to play a principal role in all stages of the dissertation project from conception to final analysis.
We pioneered in the application of atomic physics techniques for cooling and trapping of short-lived radioactive atoms with lasers at LBNL’s 88” cyclotron. The 22-sec isotope 21Na has been the focus of much of this work. Measurements of the electron-neutrino correlation have reached the 1% level. These measurements test how well the weak interaction is described by a pure V – A theory as expected in the Standard Model. The methods are being adapted to measure other decay correlations in 21Na and in the beta decays of other nuclear systems.
Our group leads a US collaboration of ten universities who, along with a large Japanese group, built and operate the KamLAND experiment at the Kamioka underground laboratory in Japan. KamLAND is a 1000-ton liquid scintillator capable of detecting electron neutrinos and anti-neutrinos. KamLAND provided the most direct evidence for neutrino oscillations and the best measurement of the some critical neutrino oscillation parameters. An upgraded KamLAND starts data taking for a measurement of low-energy solar neutrinos in 2008.
Recently we were successful in obtaining US funding for CUORE, a new search for neutrino-less double beta decay in 130Te. CUORE aims to discover whether or not the neutrino is its own antiparticle. The experiment is being constructed at the Gran Sasso Underground Laboratory in Italy. CUORE will the largest cryogenic bolometric detector every constructed. A prototype of CUORE called CUORICINO is operating. CUORICINO is currently the most sensitive operating neutrino-less double beta decay detector, worldwide.
A number of other experiments are in their final stages of analysis in preparation for publication. Examples are: a precision measurement of the vector-coupling constant from 10C beta decay, a test of time-reversal-symmetry violation in neutron beta decay, and a new measurement of the pseudo-scalar weak coupling of the nucleon. There are new opportunities to conduct fundamental “table-top” experiments and experiments in nuclear astrophysics at the 88” cyclotron and other appropriate small accelerator facilities.
For a report on the future of neutrino physics, see APS Multidivisional Neutrino Study (Stuart J. Freedman et al). The DNP/DPF/DAP/DPB Joint Study on the Future of Neutrino Physics. “The Neutrino matrix,” Nov 2004. e-Print archive: Physics/0411216.
K. Eguchi et al., “First Results From KamLAND: Evidence For Reactor Anti-Neutrino Disappearance with KamLAND”, Phys. Rev. Lett. 90, 021802 (2003)
P. A. Vetter and S. J. Freedman “Search for CPT-Odd Decays of Positronium", Phys. Rev. Lett., 91, 263401 (2003).
N. Scielzo, S.J. Freedman, B.K. Fujikawa, and P.A. Vetter. “Measurement of the beta-neutrino Correlation using Magneto-Optically Trapped 21Na”, Phys. Rev. Lett. 93: 102501 (2004)
T. Araki et al.. “Measurement Of Neutrino Oscillation With KamLAND: Evidence Of Spectral Distortion”, Phys.Rev.Lett. 94:081801 (2005)
T. Araki et al. “Experimental investigation of geologically produced antineutrinos with KamLAND.” Nature 436:499-503, July 2005
W. T. Winter, S. J. Freedman, K. E. Rehm and J. P. Schiffer. "The 8B Neutrino Spectrum" Phys. Rev. C, 73:025503 (2006)
T. I. Banks et al.,. "Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton’s Pseudoscalar Coupling gP”, Phys. Rev. Lett. (2007) (In Press)