CERN Accelerating science

Experiments at CERN
Title	Neutrino Oscillation Experiment at JHF
Author(s)	Yang, Y ; Catanesi, M G ; Magaletti, L ; Hassani, S
Experiment	RE13
Greybook	See RE13 experiment
Approved	01 December 2005
Status	Data Taking
Collaboration	T2K
Accelerator	RE
Abstract	T2K is a long baseline neutrino experiment designed to investigate how neutrinos change from one flavor to another as they travel (neutrino oscillations). An intense beam of muon neutrinos is generated at the J-PARC nuclear physics site on the East coast of Japan and directed across the country to the Super-Kamiokande neutrino detector in the mountains of western Japan. The beam is measured once before it leaves the J-PARC site, using the near detector ND280, and again at Super-K, 295 km away: the change in the measured intensity and composition of the beam is used to provide information on the properties of neutrinos. The high intensity neutrino beam is produced in an off-axis configuration. The peak neutrino energy is tuned to the oscillation maximum of ∼ 0.6 GeV to maximize the sensitivity to neutrino oscillations. The science goals of T2K can be summarized as follows: • search for CP violation in the neutrino sector • discovery of νμ → νe ( i.e. the confirmation that θ13 > 0 ) • precision measurements of oscillation parameters in νμ disappearance • search for sterile components in νμ disappearance by observation of neutral-current events • world-leading contributions to neutrino-nucleus cross-section measurements The T2K collaboration has about 500 members from 60 institutes in 11 countries. T2K began its experimental commissioning in April 2009 and to take physics data in January 2010. It suspended its operation after the major earthquake of March 2011 in order to check and repair its equipment. These repairs were completed by March 2012, and T2K began once more to take data from that time. The discovery of νμ → νe oscillations by T2K in 2013 has opened the possibility of observing CP- violation (CPV) in the lepton sector, which would be a crucial hint towards understanding the matter-antimatter asymmetry of the universe. For the contribution to the discovery of the neutrino oscillations T2K was awarded with the Breakthrough Prize in 2015. The collaboration submitted (January 2016) a proposal (now approved for the stage-1) for a second phase of the experiment in which more than 3σ sensitivity to CPV can be achieved if δCP ∼ −π /2 and the mass hierarchy is normal in a five or six year period after the currently approved running. This would require not only a beam time extension, but additional improvements including further improvements to the MR beam power, neutrino beam line, and close detectors upgrades to improve systematic uncertainties.

Contact: Catanesi, M G