Walter Toki

Professor
A.B., University of California, Berkeley, 1973; Ph.D., MIT, 1976. Fellow of the American Physical Society.

Particle Physics

My recent particle physics research includes the study of B mesons and new charmonium states at the BaBar detector which is currently taking data at the PEPII electron-positron collider at Stanford Linear Accelerator Center. The BaBar collaboration has measured Charge-Parity (CP) violation by observing a difference between the spacial decays of neutral B0 mesons and anti-B0 mesons. These results agree with the Cabbibo-Kobayashi-Masekawa model which predicted CP violation in the decays of quarks. Another topic from the BaBar experiment is the discovery of new mesons, such as the X(3872) and the Y(4260) states, produced in B meson decays. These new mysterious states cannot be explained by the charmonium or simple quark model and might be evidence for hybrid states formed with gluons and quarks.

My new research area is the study of muon neutrino oscillations into electron neutrinos in the T2K experiment in Japan. In this experiment, muon neutrino beams from the J-PARC accelerator are sent 280 kilometers underground to the Super-Kamiokande detector (SK) in the Kamioka mine in Japan. The SK experiment is a giant water tank surrounded by photo-multiplier tubes to detect the feeble neutrino interactions. This new experiment is scheduled to start running in 2009. If the muon neutrino is observed to change into an electron neutrino at an appreciable amount, then the next generation neutrino experiment will likely be an accelerator shooting a neutrino beam over very long distances to a very large underground detector. This physics measurement will aim to find CP violation in the decays of neutrinos.

My last research area is on future experiments such as the UNO neutrino detector, proposed for an underground mine such as the Henderson mine in Empire, Colorado.

Selected Publications

• B. Aubert et al. (BABAR Collaboration), " Observation of the Decay B-->J/ psi eta K and Search for X(3872)-->J/ psi eta," Phys. Rev. Lett. 93, 041801 (2004) .

Photo Gallery

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Super Kamiokande Detector in the Kamioka Mine, Japan

Walter Toki working on the Super K detector