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ROBERT SHROCK
Distinguished Professor
Physics and Astronomy
robert.shrock@stonybrook.edu | (631)-632-7986, Physics D-146
Research Group Website


Biography
Prof. Shrock has been a member of the C. N. Yang Institute for Theoretical Physics and Department of Physics (later also including Astronomy) since 1979. He graduated from Harvard in 1971 with an A.B. summa cum laude, majoring in physics and earned a Ph.D. in physics in 1975 from Princeton University. Early awards included Detur Prize, Herschel Prize and Phi Beta Kappa (at Harvard), and Woodrow Wilson Fellowship, NSF Fellowship, and Proctor Award (at Princeton). Some career awards include Fellow of the American Physical Society (1994), SUNY Chancellor's Award for Outstanding Research (2015), and Distinguished Professorship (2022). In addition to teaching undergraduate and graduate classes, Shrock has greatly enjoyed collaborative research with many excellent Ph.D. thesis students and postdocs while at Stony Brook.

Research Statement
Shrock’s research has mainly been in particle physics and quantum field theory. His early work dealt with construction and tests of unified electroweak gauge theories. In his Ph.D. thesis he performed the first calculation of the radiative decay of a neutral heavy lepton and calculated cross sections for neutrino reactions. In 1977, as a postdoctoral research associate at Fermilab (FNAL), he coauthored a paper calculating rates for decays that would violate lepton family number and, with B. W. Lee, he proved a theorem giving necessary and sufficient conditions for the natural suppression of processes of this type. During this period, with B. W. Lee and W. Bardeen, he obtained exact results on a quantum field theory, namely a nonlinear O(N) sigma model in the large-N limit. In 1978-79 he carried out pioneering studies on quark mixing with three quark families using data then available, generalizing earlier Cabibbo fits.


Some of Shrock’s most influential research has been in the area of neutrino physics, specifically neutrino masses and mixing. This area is important as the first confirmed physics beyond the Standard Model of particle physics. In 1978 he proposed a test using precise timing to search for long-lived neutral heavy leptons, and with C. Albright he proposed a test to observe the tau neutrino, ντ. In 1980 he elucidated the precise meaning of limits on neutrino masses derived from particle and nuclear decays. Previously, these had been stated as upper limits on “mνe” and “mνμ”. Shrock pointed out that these needed clarification, since νe and νμ are weak eigenstates, not mass eigenstates, and he specified precisely the actual experimental constraints. In conjunction with this, in 1980, Shrock presented new tests for neutrino masses and mixing and applied these retroactively to data to derive the first limits on this mixing. A particularly sensitive test is the search for massive neutrino emission in two-body leptonic decays of charged pseudoscalar mesons M++ν, where = e, μ and M+ = π+, K+ as well as heavy-quark mesons. Heavy neutrinos would also change the ratio of rates Re∕μ(M) = Γ(M+e+νe)Γ(M+μ+νμ). These heavy neutrinos would be dominantly electroweak-singlet (“sterile”) neutrinos. Shrock’s tests have subsequently been applied in dedicated experiments at many labs from 1981 to the present, including SIN/PSI, TRIUMF, KEK, BNL, Fermilab, Serpukhov, and CERN, and have yielded important information on neutrinos. Shrock elucidated electromagnetic properies of neutrinos including the 1980 calculation, with K. Fujikawa, of the magnetic dipole moment of a massive Dirac neutrino. He has worked on neutrino oscillations and has contributed to planning of experiments on neutrino physics.


Shrock has also done research in a number of other areas in particle physics, including lattice gauge theory, electroweak symmetry breaking, searches for the violation of baryon number and total lepton number, grand unification, and other ideas for physics beyond the Standard Model. For example, with M. Suzuki, in 1982 he pointed out the possibility of invisible Higgs decays and calculated rates for several such decays. Limits on these have been set most recently by the ATLAS and CMS experiments at the CERN Large Hadron Collider. Recently, with S. Girmohanta, he has worked on models of dark matter.


In more formal areas, Shrock has done research in statistical mechanics and mathematical physics including studies, with V. Matveev, S.-H. Tsai, and S.-C. Chang, of Potts models and Tutte polynomials and extensions of the Lee-Yang-Fisher program of investigating properties of spin models with variables generalized from real to complex values. With T. Ryttov, he has also performed higher-loop calculations of renormalization-group properties of various quantum field theories. The results of these calculations have provided valuable benchmarks used for comparison with lattice simulations by several lattice groups.