John Ellis (physicist) - Scientific Research

Scientific Research

Ellis' research interests focus on the phenomenological aspects of particle physics, though he has also made important contributions to astrophysics, cosmology and quantum gravity. Most of his publications relate directly to experiment, from interpreting measurements and the results of searches for new particles, to exploring the physics that could be done with future accelerators. He was one of the pioneers of research at the interface between particle physics and cosmology, which has since become a sub-specialty of its own: particle astrophysics.

Ellis' early research accomplishments are centered on the phenomenology of gauge theories. Working with Dimitri Nanopoulos and Mary Gaillard, he proposed in 1976 the so-called "Higgs-strahlung" process in which a Higgs boson is radiated from a Z-boson (this proved to be the best way to search for the Higgs boson at the Large Electron–Positron Collider), and in the same year estimated the direct CP-violation contribution to rare neutral kaon decays (which led to the success of the NA31 and NA48 experiments at CERN). Also in 1976, he published two papers suggesting techniques for finding the gluon in e+e− annihilations. The following year he predicted the mass of the bottom quark on the basis of Grand Unified Theory, before this quark was observed in experiment. In 1978 he published a frequently cited general paper on such theories, with Andrzej J. Buras, Gaillard and Nanopoulos.

In the 1980s, Ellis became a leading advocate of models of supersymmetry. In one of his earliest works, he showed that the lightest supersymmetric particle is a natural dark matter candidate. In 1991, he showed that radiative corrections to the mass of the lightest Higgs boson in minimal supersymmetric models increased that mass beyond the reach of the Large Electron–Positron Collider (LEP) searches. The search for the Higgs boson remains one of the most important topics in particle physics, motivating researchers at both the Fermilab Tevatron and at the CERN Large Hadron Collider (LHC). More generally, Ellis and collaborators pioneered the analysis of so-called "benchmark scenarios" meant to illustrate the range of phenomenology to be expected from supersymmetric models; such analyses have played a major role in evaluating the promise of various future accelerator options.

In parallel to his investigations of supersymmetric phenomenology, Ellis has also advocated phenomenological probes of quantum gravity and string theory. These probes include direct tests of quantum mechanics with the CPLEAR Collaboration and the derivation of Grand Unified Theories from string theory. In this vein, his work on tests of the constancy of the velocity of light and models of string cosmology received separate prizes from the Gravity Research Foundation.

An impression of the impact of Ellis' research can be obtained from the INSPIRE-HEP reference system for scientific papers in particle physics and related fields. As of 2008, this data base lists over 850 scientific papers of which he is an author; altogether the sum of citations is above 50,000. In 2004 a SPIRES survey ranked him as the second most-cited theoretical physicist. His publications include three papers with over 1000 citations, eight more with over 500 citations, and over 100 other papers with at least 100 citations each.