Professor of Physics Stephen Wimpenny passed away on November 21, 2022. He joined the University of California, Riverside in 1987. He was an influential leader in experimental high energy physics and played a leading role in the discovery of the top quark in 1995 by the DZero and CDF Collaborations and studies of its properties by the CMS collaboration.

Steve was born in 1956 in the United Kingdom. He attended the University of Sheffield for both undergraduate and graduate studies, receiving his Ph.D. in 1980. From 1980-84 Steve was a postdoctoral researcher at the University of Liverpool where he worked on the CERN EMC muon scattering experiment. Steve then became a CERN Research Fellow (1984-87) and transitioned to the UA1 experiment where he led studies of the muon decays of the newly discovered W and Z bosons. In 1987 Steve came to UC Riverside and joined the physics faculty in 1988. He began work on the DZero experiment, which was being constructed at the Tevatron collider at Fermilab. Working at DZero, Steve made important contributions to the muon detector construction, installation, and operation. He soon became leader of the group searching for signatures of the elusive top quark in decays to leptons (electrons and muons), and he played a central role in the discovery of the top quark in 1995 by the DZero and CDF Collaborations. He led the DZero Top Quark Dilepton Analysis group from 1992-96 and continued as a leader in top quark physics in DZero and later at the CERN Large Hadron Collider.

In 2006 Steve joined the CMS experiment at CERN where he continued studies of the top quark. He was one of the first leaders of the Top Quark Mass group in CMS.  He was the driving force on the combination of all of the CMS mass measurements as well as the combination of CMS, ATLAS, DZero and CDF results. He performed one of the first measurements of the top-antitop cross-section at the LHC. He studied the hadronization of bottom quarks (an important ingredient in the top quark mass measurement). He also searched for the very rare production of 4 top quarks, culminating in evidence shortly before he passed away. He was a long-time member of the CMS Top Quark Publication Committee, charged with producing well-written and timely publications, and just became co-chair in October.  

Steve was very active in administrative affairs at UC Riverside. He served as Physics and Astronomy Undergraduate Advisor for many years and served on numerous Academic Senate committees. He chaired both the Courses committee (2001) as well as Educational Policy (2015-2016). He also served on the Privilege and Tenure, Preparatory Education, and Academic Personnel committees.

Steve will be remembered as an accomplished leader and innovator in top quark physics. He was a highly valued professor and member of the UCR community and a mentor to many. He is survived by his wife Judy and sons Edward and Daniel.