1. NuInt111 Roman Tacik on behalf of the T2K Collaboration

2. Canada TRIUMF U. Alberta U. B. C. U. Regina U. Toronto U. Victoria York U. France CEA Saclay IPN Lyon LLR E. Poly. LPNHE Paris Germany U. Aachen Italy INFN, U. Roma INFN, U. Napoli INFN, U. Padova INFN, U. Bari Japan ICRR Kamioka ICRR RCCN KEK Kobe U. Kyoto U. Miyagi U. Edu. Osaka City U. U. Tokyo Poland A. Soltan, Warsaw H.Niewodniczanski, Cracow T. U. Warsaw U. Silesia, Katowice U. Warsaw U. Wroclaw Russia INR S. Korea N. U. Chonnam U. Dongshin N. U. Seoul Spain IFIC, Valencia U. A. Barcelona Switzerland U. Bern U. Geneva ETH Zurich United Kingdom Imperial C. London Queen Mary U. L. Lancaster U. Liverpool U. Oxford U. Sheffield U. STFC/RAL STFC/Daresbury Warwick U USA Boston U. B.N.L. Colorado S. U. Duke U. Louisiana S. U. Stony Brook U. U. C. Irvine U. Colorado U. Pittsburgh U. Rochester U. Washington ~500 Members, 59 Institutes, 12 Countries 2

3. NuInt113 The main goal of the T2K experiment is the precision measurement of neutrino oscillation parameters. In particular e appearance (  13 ) and  disappearance (  23 and  m 2 23 ), but this presentation focuses on the T2K Near Detectors. J-Parc SK Description of Detectors First Result comparing Data and MC based on CC Event Selection in Tracker Beam Normalization and Stability

4. NuInt114 The Near Detector pit houses both the off-axis (ND280) and on-axis (Ingrid) detectors 19 m 37 m 0 deg 2.5 deg

5. NuInt115 The off-axis detector is contained Inside refurbished UA1/Nomad Magnet B = 0.2 T (x) First closed in Jan 2010. Data run till July 2010. P0D ECAL and Barrel ECAL installed. Data running started again in Nov 2010.

6. NuInt116 Off-Axis Detector Elements SMRD in Magnet Yoke air gaps

7. NuInt117 P0D: neutral current  + N   + N +  0 + X x and y planes of scintillator bars interleaved with fillable water target bags and lead and brass sheets TPC: 3D imaging, determines number and orientation of charged particles, measures particle polarities and momenta, PID using ionization FGD: target mass for interactions, charged particle tracking FGD1: x and y planes of scintillator bars FGD2: interleaved with water layers SMRD: large angle  ’s, cosmic rays, beam related events originating in pit walls and magnet iron scintillator modules inserted in air gaps in magnet return yokes Ecal: complements the inner detectors with  /e/  separation capabilities 13 independent modules: layers of plastic scintillator bars with Pb absorber sheets between layers

8. NuInt118 Comparison of scintillator sub detectors: sub detectorbar dimensions (mm)channels Ingrid 10 x 50 x 12038560* P0D 33 x 17 x 2200 10400 33 x 17 x 2340 DSEcal 10 x 40 x 20403400* FGD 9.6 x 9.6 x 18648448 SMRD 0.7 x 16.7 x 875 4016 0.7 x 17.5 x 875 All use 1 mm Kuraray Y11 double clad WLS fibers; either mirrored at one end, or read out at both ends (DSECal and SMRD); either inserted in central hole in bar, or in S-shaped groove (SMRD) FGD P0D SMRD (photos not to scale) *Ingrid has 10796 channels with new modules *Complete Ecal has 22336 channels

9. NuInt119 Cosmic Ray passing through Off-Axis Detector SMRD DSEcal, FGD, and P0D have alternating horizontal and and vertical bars forming x-y layers P0D DSEcal TPC FGD

10. NuInt1110 All scintillator detectors use Hamamatsu Multi Pixel Photon Counters ( MPPC ’s) coupled to their WLS fibers. First large scale use in running experiment. All sub detectors have > 99.5% of their channels fully functional MPPC’s have an area of 1.3 x 1.3 mm 2 667 individual pixels Single avalanche peaks easily separated! But have to account for temperature variation of: gain, photon detection efficiency, dark noise rate, cross talk and afterpulsing probabilities

11. NuInt1111 Charged particles passing through TPC produce ionization electrons in the gas that drift away from central cathode towards readout planes. There, signals amplified with micromegas detectors. Pad size 7.0 x 10.8 mm 3 TPC’s total 124416 channels Imaging capability! Momentum resolution < 10% for p < 1 GeV/c

12. NuInt1112 Exploiting detector design/performance for Physics Analysis negative positive TPC PID for particles from interactions CC interaction in FGD1 Event selection for  CC analysis relies on identification of   resolution for deposited energy is ~8% for MIPs better than the design requirement of 10%

13. NuInt1113 FGD1 e candidate with shower in DSEcal For separation of various interaction modes:  identification in P0D and Ecal can be used for   PID Michel decay tagging in scintillator detectors will provide additional    PID

14. NuInt1114. Result: Comparison of Data and Monte Carlo (Neut) CC Event Selection using only Tracker (TPC & FGD) information (2.9 x 1019 POT) See Laura Monfregola’s talk (Session 3) for CCQE analysis N data /N MC = 1.061 ± 0.028 (stat) (det sys) ± 0.039 (phys model) + 0.044 - 0.038 Derived from consideration of many effects, eg. TPC tracking efficiency, charge misidentification, TPC/FGD hit matching, etc. Use  + event selection and through-going event sample for studies From variations of  of various interaction modes relative to CCQE; in the CCQE shape; in  FSI parameters and nucleon ejection model

15. NuInt1115 Neutrino Flux Prediction Simulation starting with 30 GeV protons upstream of the target is done with JNUBEAM (based on GEANT3). Hadronic interactions inside target core modelled starting with FLUKA2008, then tuned using the results of the SHINE/NA61 experiment at CERN (preliminary pion multiplicities using thin target for now). Uncertainties have been carefully studied. Effects related to both hadronic interactions and beamline settings have been considered. The latter include primary beam optics, horn alignment, target alignment, horn current, and horn magnetic field. Full NA61 thin target analysis + kaon multiplicities and full target data will reduce uncertainties.

16. NuInt1116 SK off-axis angle is measured by Ingrid: 2.519 ± 0.021 deg Beam position is stable over time

17. NuInt1117 Ingrid monitors neutrino event rate, which is also stable with time. Based on counting (mainly) CC interactions Comparison with (Neut) MC gives: Data/MC = 1.073 ± 0.001 (stat) ± 0.040 (syst)

18. NuInt1118 Delivered protons Feb to Dec ‘10 Nov ’10 to Feb ‘11 1x10 20 POT on Feb 8, 2011 Aiming for 150 kW x 10 7 s (3x10 20 POT) by July 2011

19. NuInt1119 Near Detectors are performing at or above specifications. Reconstruction and simulation software maturing to the point where we can perform a CC analysis and demonstrate good agreement between data and MC. Beam is stable, with steadily increasing power. Installation of P0D Ecal and barrel Ecal, completing ND280, will enable more complete and detailed analyses in the near future.