University of Texas
Jack L. Ritchie
August 14, 1955–

He next moved to Stanford University where he was a Research Associate from 1984-1986, conducting experiments at SLAC and at Brookhaven National Laboratory. He was an original collaborator in a new experiment at BNL to search for a very rare K_L decays. Jack’s research focused on an experiment to search for the decay of long-lived neutral kaons to lepton pairs that did not conserve so-called separate lepton number.  If these separate lepton number violating decays were observed, it would demonstrate the existence at high mass scales of a physical process outside the standard model of particle physics. Brookhaven National Laboratory (BNL) had suitable accelerator facilities that provided sufficiently intense beams of neutral kaons.  Karol Lang joined the UT faculty in 1991 as assistant professor, and he also focused his early research on this experiment, which succeeded in achieving unprecedented sensitivity to these types of decays. 

Jack had been a leader in the multi-university collaboration that conducted this experiment, and he subsequently helped steer the collaboration to undertake a much-improved second round of the experiment that relied on the radical idea of stopping the neutral beam inside the detector.  This required developing a novel beam-stop that would absorb most byproducts from neutron and kaon interactions (primarily low-energy neutrons and photons).   Most of this development was carried out by the UT group that included Jerry Hoffmann and Peter Riley who joined this new BNL experiment.  Karol Lang developed new so-called straw drift chambers for the experiment, and a number of other detector improvements were made.  Data was collected in 1995 and 1996.  Ultimately the second-generation experiment was a success, reaching the best sensitivity ever achieved in any kaon experiment.  It made the first observation of the decay of neutral long-lived kaons to electron-positron pairs, a final state that appears only once in about 1011 decays.  This remains today the rarest decay mode ever observed in particle physics experiments, more than two decades later. 

In 1986, Jack was appointed Acting Associate Professor at Stanford. In 1988, he joined the Uniiversity of Texas as an Assistant Professor of Physics. He was promoted to Assoiciate Professor in 1993 and Professor in 2001. From 1999 to 2001, Jack was on leave from UT serving as Senior Program Officer, Office of High Energy and Nuclear Physics, Office of Science at the U. S. Departmnt of Energy in Washington, DC. While at DOE, his primary responsibility was coordinating the oversight of the high-energy physics programs of U.S. national laboratories, most notably the Fermi National Accelerator Laboratory (aka Fermilab). 

Following his 2 ½ years at DOE, he worked on an electron-positron colliding beam experiment at SLAC from 2002 to about 2015. The experiment, known as BaBar, used an electron-positron storage at SLAC to produce large samples of B and anti-B mesons (B mesons contain a bottom quark and have mass more than five times greater than the proton).  The BaBar experiment was the first to observe the phenomenon of CP-violation outside the kaon system.  Jack’s UT group focused on measurements of rare flavor-changing neutral current B meson decays, leading to state-of-the-art results for several modes.  In addition, Jack took on a management responsibility for the experiment’s electromagnet calorimeter system for three years, and he served regularly in significant roles in the collaboration, including membership in the Publications Board and Executive Board.  Jack’s work on BaBar continued until 2015. 

In February 2015, he was appointed Chair of the Department of Physics, a position he held until January 2022. He served as Director, Center for Particles and Fields, UT Austin, from 2010 until his retirement in 2022.

Jack retired January 2022.

Honors

Jack's honors included Fellow, American Physical Society 2003 recipient, Division of Particles and Fields Fellowship. "For his contributions to experimental high energy physics, particularly his leadership in the E871 experiment, the most sensitive search available for lepton number violations in K_L decays."

Sambamurti Lecturer 1993, Jack L. Ritchie, in recognition of his outstanding contributions to the study of rare and forbidden kaon decays at the BNL AGS. This is a prize lectureship established in memory of Aditya Sambamurti, a young high energy experimentalist working on rare kaon decays at the BNL AGS, who died in 1992. It is to be awarded yearly to a young (within 20 years of their Ph.D.) high energy or heavy ion experimentalist of outstanding achievement. The lecture describing the work for which the lecturer is being honored, is to be delivered at the RHIC/AGS Users Meeting. Here is a link to Jack Ritchie's lecture: 1993 Award Video

Research

Research in experimental particle physics:
- Measurement of anomalous magnetic moment of the muon at Fermilab, 2015–2018
- Measurement of B-meson decays and related processes, including CP violation, in electron-positron collisions in the BABAR experiment using the PEP-II B-factory at the SLAC National Accelerator Laboratory, 2001–2015
- Rare decays of neutral long-lived kaons in experiments at the Brookhaven National Laboratory, 1984–2000
- Open charm production with hadron beams at Fermilab, 1979–1983 (Ph.D. research)

Link to 1995 article on Rare Kaon Decay: Rare Kaon Decays