First results from T2K: electron neutrino appearance

June 15, 2011

The T2K collaboration has submitted their first physics paper to Physical Review Letters. In it they report the most significant evidence to date that muon neutrinos transform into electron neutrinos. This transformation is governed by a previously unmeasured parameter of nature, called θ13 ("theta one three"). The neutrinos are produced in a beam by the J-PARC accelerator. They travel 295 kilometers through the earth's crust, and are detected in the Super-Kamiokande detector across Japan. In this paper T2K reports the detection of six electron neutrino events in a carefully controlled beam that should have at most 1.5 electron neutrino events. The probability that T2K observe as many as six by chance is less than one percent. The publication of this result is accompanied by a press release from the accelerator labs KEK/J-PARC.

The Boston University authors on this paper include graduate student Mike Litos, research associate Jen Raaf, and Profs. Ed Kearns, Jim Stone, and Larry Sulak. The BU neutrino group has been involved in a series of neutrino experiments using the Super-Kamiokande detector for more than 15 years, thanks to support from the US Department of Energy's Office of Science.