Evelyn Thomson

The next few years will be a very exciting time at the high energy frontier of experimental particle physics, with many interesting opportunities for undergraduate and graduate research! I work on precision measurements of top quark properties with the CDF experiment at the Tevatron Collider, which will continue to run through at least 2008 at Fermilab near Chicago. In future, I plan to search for new physics with the ATLAS experiment at the Large Hadron Collider, which will commence operation in 2007 and run through at least 2015 at CERN near Geneva, Switzerland. In 2005, my research was recognised with an Outstanding Junior Investigator Award from the U.S. Department of Energy.

Throughout my career, I have been fascinated by the mystery of mass - what is the missing piece that gives mass to the fundamental particles of the universe? I started by developing the technique and performing one of the first measurements of the W boson mass with the ALEPH experiment at CERN. The W boson carries the weak nuclear force, esssential for the nuclear fusion reactions that power stars, and was discovered in 1983 at CERN. The W boson acquires mass in the standard model of particle physics via the hypothetical, much-hunted but exceedingly elusive, Higgs boson. Interpretation of improved measurements of the W boson mass in the context of the standard model of particle physics leads to a better constraint on the unknown mass of the as-yet-undiscovered Higgs boson - and a better idea of where and how to search for it.

The top quark is by far the most massive of the sixteen known fundamental particles, and has approximately the same mass as a gold nucleus. Intrigued by the possibility that the unexplained large mass of the top quark could be due to effects from physics beyond the standard model, I decided to measure the production rate of top quarks at CDF since a deviation from theoretical predictions could indicate new physics in top quark production or decay. To do this, I developed a novel measurement of the cross section with an advanced multivariate technique. Postdoctoral researcher Dr. Aafke Kraan and I analyzed the angular distribution of the decay products of the top quark in order to search for the presence of particles beyond the standard model in top quark decay. The paper on this work has been published by Physical Review Letters, and Dr. Kraan has won a Marie Curie Fellowship from the European Union. Postdoctoral researcher Dr. Chris Neu is currently studying the production of W bosons with associated heavy flavor jets, which is the dominant background to top quark pair production, single top quark production, and one of the search channels for the standard model Higgs boson.From April 2004 to April 2006, I was co-leader of the CDF Top Quark Physics Group, which consisted of over 100 active researchers, including over fifty graduate students from universities in the U.S. and abroad.

From 2007, I will focus a significant fraction of my research effort on the ATLAS experiment. With postdocs James Degenhardt and Sasa Fratina, my group looks forward to helping to commission the ATLAS detector and to exploring the new energy frontier to be opened up by the CERN LHC. Research on ATLAS will require a great deal of creativity in a range of areas, from novel approaches in searches for signatures of new massive fundamental particles to achieving an excellent understanding of a detector with 150 million channels to be read-out every 25 nano-seconds!