Button to scroll to the top of the page.

Jack L Ritchie

Professor, Department Chair
College of Natural Sciences

Experimental HEP; rare decays


Phone: 512-471-4488

Office Location

Postal Address
The University of Texas at Austin
2515 SPEEDWAY, Stop C1600
AUSTIN, TX 78712-1192

Ph.D., University of Rochester (1983)

Research Interests

Experimental HEP; rare decays.

My research is in experimental particle physics, also called high energy physics. This branch of physics studies nature on the subatomic scale, using very high energy particles as probes. Accelerators are usually needed to produce the particles. 

Particle physics interested me when I was a student since it looks for simple answers to profound questions. An example would be understanding the structure of matter in terms of fundamental building blocks, the quarks. Since I was a student, the field has progressed a lot, with available energies and intensities of particle beams increasing by orders of magnitude. At the same time, the size of the experiments and the number of physicists who work on a single experiment has increased. This is because the size, complexity, and cost of detectors has grown, and the size of collaborations has had to follow the trend. The experiment that was the basis for my Ph.D. had 16 collaborators. My current experiment has about 400, but things have not changed as much as you might expect. We typically still work in relatively small groups on well-defined problems. In a larger collaboration, coordination of these smaller efforts is important, but we know how to do that.

A theme in my research over many years has been a focus on the rare decays of the K and B mesons that are sometimes called “flavor changing neutral current” (FCNC) decays. These have been important in establishing the Standard Model, and they are still important because they are particularly sensitive to the possible existence of new interactions beyond the Standard Model.

For the last several years, I’ve been part of a collaboration working at SLAC on an experiment called BaBar. The name (based on the French elephant of children’s books) is supposed to be cute, but is motivated by the fact that the experiment studies the decays of B and anti-B (“Bbar”) mesons. The B and Bbar mesons are produced from the decays of a state called the Upsilon(4S), which a bound state of a b and anti-b quark that is produced in large numbers by the PEP-II B-factory at SLAC.

BaBar has had lots of important results, spanning many topics: CP violation, which relates to the matter-antimatter asymmetry in the universe; the observation of numerous new states; rare decays of B-mesons, charm mesons, and tau leptons; and others. The UT Austin group has a prominent role in the study of rare FCNC B-decays with BaBar data, and this work is ongoing.
BaBar is no longer taking new data, but we have a lot of work still to do analyzing the data we have. There are also ideas for next-generation K and B decay experiments on the table, with potentially large gains in reach for “new physics,” so this line of research is likely to remain exciting.

  • Fellow, American Physical Society