William R. Molzon
Professor, Physics & Astronomy
School of Physical Sciences
PH.D., University of Chicago, 1979
B.S., California Institute of Technology
Phone: (949) 824-5987
Fax: (949) 824-2174
University of California, Irvine
3131 Frederick Reines Hall
Mail Code: 4575
Irvine, CA 92697
Experimental Particle Physics
Professor Molzon received his B.S. from Caltech and his Ph.D. from the University of Chicago in 1979. He held a postdoctoral position at CERN in Geneva, Switzerland, before joining the Physics Department at the University of Pennsylvania. He moved to UCI in 1988. He is a recipient of a Sloan Fellowship and a Department of Energy Outstanding Junior Investigator Award. He has served on a number of national advisory committees including the Fermi National Accelerator Laboratory Physics Advisory Committee and the Department of Energy High Energy Physics Advisory Panel.
Professor Molzon works in the field of experimental particle physics. His thesis research was done at Fermilab and resulted in a measurement of interactions of particles called kaons that could be used to infer the kaon size. His postdoctoral work was at CERN, the international laboratory near Geneva, Switzerland. The experiment on which he collaborated showed for the first time that high energy photons could be produced directly in the collisions of protons at high energy; this result provided evidence for the existence of gluons, the particles responsible for the strong interactions between the quarks that make up the protons and neutrons in the nuclei of ordinary matter. His experiment also provided evidence for the production of "jets" of high energy particles, which we associate with the scattering of quarks and gluons.
More recently, Professor Molzon has done experiments to test the conservation of additive quantum numbers associated with electron and muon type leptons. An outstanding puzzle in our understanding of particle physics is the existence of three "families" of quarks and leptons. They are distinguished by mass and by an additive quantum number; in the case of leptons this quantum number is apparently conserved exactly. The stable matter around us is made of particles from only one "family." The conservation laws that Professor Molzon and collaborators are testing are not understood in any fundamental sense, and this research is producing more stringent tests of their validity. In a series of experiments that he co-led at Brookhaven National Laboratory on Long Island New York, he and collaborators placed the best limits on the decay of neutral kaons to a muon and anti-electron. As a by-product, the experiment also made the world's best measurement of the rate for neutral kaons to decay into a muon anti-muon pair, and made the only measurement of the neutral kaon decay into an electron anti-electron pair. Professor Molzon and his group (first at the University of Pennsylvania and then at UCI) designed and built particle detectors and custom electrons for the experiment and parts of the kaon particle beamline.
Following these successful experiments, Professor Molzon led an international team of physicist that proposed to do a very ambitious experiment to test further the conservation of muon and electron number, again at Brookhaven. The experiment received significant funding from the National Science Foundation before being canceled in 2005 due to programmatic changes in the National Science Foundation and the Department of Energy. He is now working on the implementation of a new version of that experiment at Fermilab. He is also working with an international collaboration on a related experiment (MEG) at the Paul Scherrer Institut near Zurich Switzerland.
New limit on the lepton-flavour violating decay mu -> e gamma, J. Adam et al., Phys. Rev. Lett. 107 (2011).
Physics with a High Intensity Proton Source at Fermilab: Project X Golden Book., ?Jeffrey Appel et al., FERMILAB-FN-0904 (2008).
Proposal to search for mu- N -> e- N with a single event sensitivity below 10 -16, Mu2e Collaboration (R.M. Carey et al.), FERMILAB-PROPOSAL-0973 (2008).
A Straw drift chamber spectrometer for studies of rare kaon decays, K. Lang et al., Nucl.Instrum.Meth.A522 (2004).
A maximum likelihood method for particle momentum determination, ?T. Liu and W. Molzon, Nucl. Instrum. Meth. A496 (2003).
Improved branching ratio measurement for the decay K0(L) --> mu+ mu-. ?D. Ambrose et al., Phys.Rev.Lett. (2000).
The MECO experiment at BNL: Search for mu- N --> e- N with sensitivity below 10**(-16), ?W. Molzon, JHF science, vol. 2 (1998).
Improved Upper Limit on the Branching Ratio B(KL -> mu e), K. Arisaka et al., Phys. Rev. Let. 70, 1049 (1993).