1 Status of the T2K long baseline neutrino oscillation experiment Atsuko K. Ichikawa (Kyoto univeristy) For the T2K Collaboration

2 The T2K Experiment sub GeV pure  beam J-PARC 0.75MW E P =30GeV) Super-K: 50 kton Water Cherenkov Physics goals Discovery of  e appearance Precise meas. of disappearance  x Discovery of CP violation (Phase2)

3 T2K Collaboration 12 Countries Canada, France, Germany, Italy, Japan, Korea, Poland, Russia, Spain, Switzerland, UK, USA ~ 450 members

4 T2K Layout p  120m0m280m 2 km 295 km on-axis off-axis Quasi-monochromatic, sub-GeV Off-Axis Beam ~ 2,200 (~1,600)  (CC) interactions at Super-K [40GeV, OA2.5 o, 22.5 kt-yr] 2.0~2.5 o Super-K P  (GeV/c) E (GeV) 3o3o 2.5 o  =2 o 0123 E  (GeV) Flux  (arbitrary unit)  =2 o 2.5 o 3o3o  m 2 atm = 2.0~3.0x10 -3 eV 2 [ E  = 0.48~0.72GeV ] -mon

5 The Far Detector: SK-IV  ICRR, Univ. of Tokyo New Electronics and DAQ installation completed in ’08. Super-K is ready.

6 SK Typical Event Display Back ground for e appearance search – Intrinsic e component in initial beam – Merged  0 ring from Neutral Current interactions  e 00 good  -e separation

7 Sensitivity to  13 BG subtraction: 10% error at  CP =0/  (OA2.5  ) 5  POT sin 2 2  13 = 0.1 [sin 2  23 = [sin 2  23 = ½ ]  m 23 2 = 2.5x10 -3 sin 2 2  13 Background in Super-K Signal [~40% eff] Signal + BG  e total # of events in E rec=0.35~0.85 [GeV]

8 Measurement of  23,  m 23 2 Use 1R  -like events –Large QE fraction Clear deficit is expected in the reconstructed energy –  E=  E  rec-E  true) ~ 60MeV ⇔ < 10% measurement on  m E rec (GeV) m2m2 sin 2 2  R(measured / expected)  + n →  + p -- p ( E , p  )  E rec QE inelastic E  (reconstructed) – E  (true)  E~60MeV

9 Sensitivity:   disappearance Goal : (sin 2 2  )~0.01, (m 2  ) <1×10 -4 [eV 2 ] (OA2.5  )  m 2 [10 -3 eV 2 ] --68%CL --90%CL --99%CL K2K & SK T2K 5  POT (Stat. only) ~ full Intensity MC Stat. only

10 J-PARC Accelerators The Hadron Hall MR A round=1,568m Materials & Life Science Experimental Facility 3GeV RCS A round=348m Linac(330m) Neutrino Area for Transmutation Experimental Facility [Feb.2006 ] [Feb.2006 ] 181 MeV Jan. ‘07 3 GeV Oct. ‘07 30 GeV Dec. ‘08 Apr. ‘09

11 The Neutrino Beam-Line One out of three installed. Magali’s talk

First shot of the proton beam SSEM (Segmented Secondary Emission Monitor) Fluorescent Image

13 Muon Monitor 10m 4m Decay Volume Dump 4 m 1.5 m

14

15 First beam event in Muon monitor and evidence of neutrino production Silicon PIN photodiode Scintillator for reference FADC gate 1  sec 15 mV

16 Horn focusing Horn off Horn on MUMON Silicon PIN photodiode array

17 Achievement in this April and May Nominal intensity: ~4x10 11 p/bunch, 1 bunch/spill (~0.1% of design intensity) Superconducting combined-function magnets are working well as expected. Beam monitors are working well. – Intensity monitors, beam position monitors, beam profile monitors are working well. –Beam position at the target is confirmed with the fluorescent plate. –Secondary muons are observed behind the beam dump. The focusing effect of the electromagnetic horn is confirmed. Successfully passed the government inspection.

18 From Now Complete set of 3 horns and installation of ND280 detectors scheduled for the end of this Fall. 100kW commissioning in JFY kW commissioning in JFY2009 Physics run from 2010  fist resultPhysics run from 2010  fist result Beyond 100kW: 100  750kW(Design)Beyond 100kW: 100  750kW(Design) –Beam loss control –Linac 400 MeV energy recovery and upgrade of the RCS injection system Long-term plan toward power frontier (~MW)Long-term plan toward power frontier (~MW) –KEK roadmap