1. Particle Physics Seminar

    "Observation of Electron Neutrino Appearance from a Muon Neutrino Beam and more"

    Presented by Chang Kee Jung, Stony Brook University

    Friday, November 22, 2013, 10:30 am
    Small Seminar Room, Bldg. 510

    Hosted by: David Jaffe

    In 2011, T2K published a result that reported a non-zero $\theta_{13}$, the last unknown mixing angle in the lepton sector at that time, at 2.5 sigma level of significance which was the first evidence of non-zero $\theta_{13}$ by a single experimental measurement. Recently, after analyzing two more years of data taken since 2011, the T2K experiment reported "Observation of electron neutrino appearance from a muon neutrino beam" at 7.5 sigma level of significance. While neutrino oscillation has been well-established since the discovery by the Super-Kamiokande experiment in 1998, there have not been a definitive observation of neutrino oscillation in a so-called "appearance mode", and this new T2K observation is the first time an explicit neutrino flavor (electron) appearance is observed from another neutrino flavor (muon). This observation also opens the door to study CPV in neutrinos. When incorporating recent precision measurements on $\theta_{13}$ by the reactor experiments, especially Daya Bay, along with other neutrino oscillation parameter measurements, T2K data show an intriguing initial result on the $\delta_{CP}$. In this talk I will present the details of this discovery and its importance to the future CP-violationmeasurements in the lepton sector. I will also describe the T2K experiment in some detail, and present other recent results, in particular results from the muon neutrino disappearance studies using full T2K Run 1-4 data.