Thursday, October 27, 2011, 16:00
WHGA/001
A. Rubbia, ETHZ
Abstract:
T2K (Tokai-to-Kamioka) is a long-baseline neutrino oscillation experiment primarily searching for
oscillations of muon neutrinos into electron neutrinos. T2K will also make precise measurements of
the atmospheric oscillation parametersvia muon neutrino disappearance. The experiment uses 30 GeV
protons from the new J-PARC Main Ring accelerator, located in Tokai, Japan,to generate a
conventional neutrino beam to the Super-Kamiokande far detector. The hadron production
measurements of the NA61 experiment at CERN were used to predict the neutrino fluxes at the near
and far detectors. The T2K oscillation analysis compares the rates of observed and predicted muon
and electron neutrino candidates in the far detector. We present first results based on data
accumulated from January 2010 to March 2011. Six electron neutrino events pass the selection
criteria for electron appearance at Super-Kamiokande, whereas the expected number of background
events is 1.5 ± 0.3. The probability of a fluctuation of the background is 0.7% (2.5sigma
significance). Our conclusion is that we observe an indication of numu-> nue appearance, opening
the way to search for CP violation in the leptonic sector. We will also discuss implications of
this result on the future of neutrino physics.