John Ellis (physicist)

Infobox Scientist
name = John Ellis

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imagesize =250px
caption = John Ellis at the University of Heidelberg in February 2008
birth_date = 1946
birth_place = London
nationality = Great Britain
field = Physics
prizes = Maxwell Medal (1982), Dirac Medal (2005)

John Ellis is a British theoretical physicist born in 1946 in London. (His first name is sometimes listed as Jonathan.) He attended Cambridge University, earning his Ph.D. in theoretical (high-energy) particle physics in 1971. After brief post-doc positions at SLAC and CalTech, he went to CERN and has held an indefinite (i.e., permanent) contract there since 1978. He has been awarded several major honours, including the Maxwell Medal in 1982, the Dirac Medal in 2005, and is an Elected Fellow of the Royal Society of London since 1985, and of the Institute of Physics since 1991. He was awarded an Honorary Doctorate from the University of Southampton, and twice won the First Award in the Gravity Research Foundation essay competition (in 1999 and 2005).

Ellis' activities at CERN are wide-ranging. He was twice Deputy Division Leader for the theory ("TH") division, and served as Division Leader for 1988 - 1994. He was a founding member of the LEPC and of the LHCC; currently he is chair of the committee to investigate physics opportunities for future proton accelerators, and is a member of the extended CLIC (Compact Linear Collider) Steering Committee.

cientific 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 [ [http://www.slac.stanford.edu/spires/find/hep/www?j=NUPHA,B106,292 A Phenomenological Profile of the Higgs Boson by John R. Ellis, Mary K. Gaillard, Dimitri V. Nanopoulos, "Nucl.Phys.B106:292,1976"] ] (this proved to be the best way to search for the Higgs boson at LEP), and in the same year estimated the direct CP-violation contribution to rare neutral kaon decays [ [http://www.slac.stanford.edu/spires/find/hep/www?j=NUPHA,B109,213 Lefthanded Currents and CP Violation by John R. Ellis, Mary K. Gaillard, Dimitri V. Nanopoulos, "Nucl.Phys.B109:213,1976"] ] (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 [ [http://www.slac.stanford.edu/spires/find/hep/www?j=NUPHA,B111,253 Search for Gluons in e+ e- Annihilation by John R. Ellis, Mary K. Gaillard and Graham G. Ross, "Nucl.Phys.B111:253,1976, Erratum-ibid.B130:516,1977"] ] . 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. [ [http://www.slac.stanford.edu/spires/find/hep/www?j=NUPHA,B135,66 Aspects of the Grand Unification of Strong, Weak and Electromagnetic Interactions by John R. Ellis, Mary K. Gaillard, Dimitri V. Nanopoulos, "Nucl.Phys.B135:66-92,1978"] ]

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 [ [http://www.slac.stanford.edu/spires/find/hep/www?j=NUPHA,B238,453 Supersymmetric Relics from the Big Bang by John R. Ellis, J.S. Hagelin, Dimitri V. Nanopoulos, Keith A. Olive and M. Srednicki, "Nucl.Phys.B238:453-476,1984"] ] . 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 LEP searches [ [http://www.slac.stanford.edu/spires/find/hep/www?j=PHLTA,B257,83 Radiative corrections to the masses of supersymmetric Higgs bosons by John R. Ellis, Giovanni Ridolfi and Fabio Zwirner, "Phys.Lett.B257:83-91,1991" ] ] . 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 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 [ [http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ph/0106204 Proposed post-LEP benchmarks for supersymmetry by Marco Battaglia, Albert De Roeck, John R. Ellis, Fabiola Gianotti, Konstantin T. Matchev, Keith A. Olive, Luc Pape and Graham Wilson, "Eur.Phys.J.C22:535-561,2001" ] ] ; 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 SPIRES 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 40,000. In 2004 a SPIRES survey ranked him as the second most-cited theoretical physicist. His publications include one paper with over 1000 citations, six more with over 500 citations, and 104 other papers with at least 100 citations each.

upport of Particle Accelerator Projects

In addition to his theoretical research, John Ellis has been an advocate and supporter of future accelerators, beginning with LEP and the LHC, and extending to CLIC, photon colliders, and future proton accelerators. Naturally his theoretical work reflected these connections, as when he showed that data from the SLC and from LEP could be used to predict the masses of the top quark and the Higgs boson. Such predictions are now a main stream activity within particle physics, and constitute one of the most important bridges between the experimental and theoretical communities.

Concerning the LHC, Ellis played a leading role in the seminal 1984 workshop on physics to be done with such an accelerator. Since then he has written many articles on searches for Higgs bosons and supersymmetric particles at the LHC, both for the pariticle physics community and at a more popular level. His most recent LHC physics review appeared in a Nature Insight supplement on July 19, 2007.

John Ellis has been a strong supporter of the CLIC option for a future high-energy e+e- linear collider; this option is pursued most strongly at CERN. He was convenor of the CLIC Physics Study Group the produced the main report on this option, in 2004.

Outreach and Spreading Physics around the World

Ellis is frequently invited to give public lectures on particle physics and related topics. For example, in the two-year period 2004-5, he gave public lectures in Geneva (in French), in Granada and Barcelona (in Spanish), in Rome (in Italian) and in Warsaw (in English).While at CERN he often gives introductory talks to visitors, ranging from official delegations from the United Kingdon to physics teachers at the high-school level.

Ellis is well known for his efforts to involve non-European nations in CERN scientific activities. In the context of the LHC, he has interacted frequently with physicists, administators at universities and institutes and ministers of funding agencies and diplomatic corps from a wide variety of countries, ranging from major CERN partners like the United States, Russia, Japan, Canada, India, Israel and China, to states with nascent physics programs such as Azerbaijan, the Baltic republics, Bolivia, Columbia, Croatia, Cyprus, Iran, Madagascar, New Zealand, Pakistan, Romanie, Sri Lanka, Vietnam, and many others. These interactions have fostered the international character of CERN and opened the pathways of scientific discourse all around the world.

References

External links

* [http://www.nytimes.com/2007/05/15/science/15cern.html?pagewanted=1&_r=1&hp Ellis discusses the supercollider at CERN, and the physics discoveries that could come from it]
* [http://cdsweb.cern.ch/record/1120625?ln=en "The LHC is safe", talk given by John Ellis at CERN, in Geneva, on 14 August 2008]
* [http://cosmiclog.msnbc.msn.com/archive/2008/09/10/1357334.aspx International Man of Mysteries, September 10, 2008 (Interview with John Ellis)]