Status of the T 2 K experiment K

Status of the T 2 K experiment K. Matsuoka (Kyoto Univ. ) for the T 2 K collaboration Contents Physics motivations (neutrino oscillation) Concept of the T 2 K experiment Beam commissioning results XLVth Rencontres de Moriond

The T 2 K (Tokai-to-Kamioka) experiment 50 -kt water cherenkov 2 30 -Ge. V 750 -k. W proton beam Tokai Kamioka 295 km J-PARC(*1) Super-K(*2) Kamioka 2. 5˚ nm beam Tokai Ø Search for nm ne (ne appearance) Ø Precise measurement of nm nx (nm disappearance) *1 Japan Proton Accelerator Research Complex *2 The Super-KAMIOKANDE detector. See Yamada-san’s talk

T 2 K collaboration 12 countries (Canada, France, Germany, Italy, Japan, Korea, Poland, Russia, Spain, Switzerland, UK, USA) ~500 collaborators from 62 institutions 3

Neutrino oscillation 4 Neutrino changes its flavor while propagating in vacuum/matter. Neutrinos have masses = Evidence for physics beyond the Std. Model. Flavor eigenstates ne nm nt Atmospheric & accelerator q 23 = 37˚ ~ 45˚ Dm 23 ≈ 2. 4 x 2 10– 3 Mass eigenstates m 1 Reactor & accelerator e. V 2 m 3 Solar & reactor q 13 < 10˚ by CHOOZ m 2 q 12 ≈ 34. 4˚± 1. 3˚ Dm 122 ≈ 8 x 10– 5 e. V 2 Mass hierarchy (m 1 < m 2 < m 3 or m 3 < m 1 < m 2)? Size of the mixing angle q 13? Size of the CP phase d? … Ability to measure CP violation depends on sinq 13. Important to measure q 13.

Concept of T 2 K Probability 5 Ø Probability of nm nx (q 23, Dm 232) ~0. 5 CC-QE(*) events to measure En Off-axis beam configuration Dm 322 = 2. 8 x 10– 3 e. V 2 L = 295 km sin 22 q 295 km Ø Probability of nm ne (q 13) < 0. 13 D m 2 CC-QE nl p ql l Adjust En to ones around the oscillation max. Reduce high energy ns’ B. G. from non CC-QE. High statistics J-PARC + Super-K + off-axis beam Expected event rate in Super-K: ~700 CC interactions (for 750 k. W x 107 sec) Far-to-near flux extrapolation Off-axis beam nm p q m Measure n flux, energy and flavor both at the near (ND 280) and the far (Super-K) detectors. * CC-QE: Charged Current Quasi-Elastic

Measurement of nm nx Nnnull = R x Fn. ND x snwater Nnobs R(Far/Near) Extrapolation by MC Measurement by Super-K which is experimentally verified by NA 61(*) Fn. ND 6 Uncertainty is reduced by • ND 280 for Fn. ND and snwater • Beam monitoring for R P ( n m n x) Measurement by ND 280 MC MC Target 0 m D m 2 MC sin 22 q = 1. 0 Dm 2 = 2. 7 x 10– 3 e. V 2 (8. 3 x 1021 POT @ 30 Ge. V) ND 280 ~280 m Super-K 295 km * See Nicolas’ talk Accurate prediction of Nnnull is important to measure q 23 and Dm 322 precisely.

Search for nm ne ne signal 1 -ring e-like event (CC-QE) Background Beam ne contamination 7 Sharp edge Super-K event display Fussy ring m e CC-QE mis-PID probability: ~1% (~0. 4% of nm at nm spectrum peak energy) Mis-reconstructed NC(*1) p 0 event(*2) (mainly from high E ns reduced by the off-axis beam) Measurement by Super-K Expected num. of events p 0 in 0. 35 -0. 85 Ge. V sin 22 q 13 MC Signal 143 14 Beam ne BG Nnobs 0. 1 16 16 BG from nm 10 10 0. 01 (sin 22 q 13 < 0. 13 by CHOOZ) nm N p 0 N nm g g *1 NC: Neutral Current *2 See Joshua’s talk

T 2 K sensitivity 8 30 Ge. V, 8. 3 x 1021 POT, d. CP = 0 M. Diwan, Venice, Mar. 2009 CHOOZ excluded > 10 times d(sin 22 q 23) ≈ 0. 01, d(Dm 232) < 10– 4 e. V 2 0. 0060 @ Dm 232 = 2. 4 x 10– 3 e. V 2 (for a 10% sys. error)

T 2 K neutrino beam 9 M ain Rin g Top view (n beamline) High power beam Target & horns Beam loss has to be held as low as possible. Shift of the proton beam on the target makes a shift of the n beam direction. Beam dump m monitor Necessary to tune and monitor the proton beam. Off-axis beam configuration INGRID ND 280 En spectrum peak shifts according to the n beam direction (DEpeak = 2%/mrad). Necessary to tune and monitor the n beam direction precisely (w/in 1 mrad). Side view p Target & horns 0 p nm m Beam dump m monitor 118 m Slope: ~40 2. 5˚ INGRID Super-K ND 280 ~280 m

Beam commissioning 10 Purpose Check all components (the magnets, beam monitors, horns, DAQ, etc. ) work as expected. Tune the proton beam orbit and the pos. /size at the target. Tune the n beam direction by the muon monitor and INGRID. Establish operation of the n detectors (ND 280 and Super-K). ne appearance search started. 1 st horn only Construction Full horn setup Beam commissioning ~20 k. W ~100 k. W Super-K On-axis detector (INGRID) Off-axis detector (ND 280) Summer 2010 ne search Jan. 2010 Beam commissioning Nov. Jun. Apr. 2009 ~1 k. W Horn 2, 3 installation

Proton beam monitors CT (intensity) x 5 ESM (position) x 21 11 Beam loss monitor x 50 SSEM (profile) x 19 OTR (position & profile) @ target Horizontal beam orbit Before tuning ± 1 mm After tuning OTR x = – 0. 5 mm MR extraction Proton beam orbit was tuned by using the proton beam monitors. Deviation of the orbit from the beam line is less than 1 mm. The beam loss is enough small. Proton beam hits the center of the target. Target

Muon monitor Required precision of the profile center: Better than 11. 8 cm (= 1 mrad) 3 cm 12 Monitor the neutrino beam flux and direction on a shot-by-shot basis by measuring the muon profile. Measures ionization yield by muons at each sensor to reconstruct the profile. Beam direction is a direction from the target to the profile center. 7 x 7 Si PIN photodiodes 25 min. RMS 1. 8 mm 7 x 7 ionization chambers ± 1 mrad m beam RMS 2. 9 mm Silicon PIN photodiodes • No time dependent drift. Silicon x slice • Further beam tuning was ongoing at this time. Muon monitor measures the beam direction stably w/ a precision much better than 1 mrad.

Neutrino beam monitor (INGRID) 13 Monitor the neutrino beam flux and direction w/ ~1 -day statistics by measuring the on-axis neutrino profile. Counts neutrino (CC-QE) events in each module to reconstruct the profile. Required precision of the profile center: Better than 28. 0 cm (= 1 mrad) 5 cm 7 + 7 modules Event rate of each module for 7. 3 x 1015 POT m am ea be nb 1 st event (Nov. 22, 2009) Inc. n events outside the modules m n n events inside the modules p like Fe + scintillator 1 m Side view Dec. 25, 2009 Horizontal modules

Neutrino event in ND 280 14 P 0 D: p 0 Detector NC p 0 rate TPC: Time Projection Chamber PID (d. E/dx) Magnet coils Magnetic field 0. 2 T pl 0. 2 FGD: Fine Grain Detector ql T ECAL: Electromagnetic CALorimeter SMRD: Side Muon Range Detector 01: 57 JST, Feb. 5, 2010 Magnet on (0. 188 T) FGD 1 FGD 2 DSECAL P 0 D 7. 0 m n beam net ( Mag P 0 D 3. 5 m 3. 6 m UA 1 magnet ECALs TPCs FGDs yoke & SMRD Measure Fn. ND and sn ) open n beam TPC 1 TPC 2 TPC 3 Detected the neutrino event w/ the full setup. Calibration of the detectors is ongoing.

T 2 K 1 st neutrino event in Super-K 06: 00 JST, Feb. 24, 2010 3 rd ring 2 nd ring 1 st ring [ 1 st ring + 2 nd ring ] Invariant mass: 133. 8 Me. V/c 2 (close to p 0 mass) Momentum: 148. 3 Me. V/c 15

Summary Neutrino oscillation is physics beyond the Std. Model. The T 2 K long baseline neutrino oscillation experiment started searching for the ne appearance. The beam commissioning succeeded; all the components are working as expected. The beam direction can be measured precisely by the muon monitor. The beam line parameters have been fixed. 100 k. W x 107 sec data will be accumulated in 2010. First physics result is expected around summer 2010. 16

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J-PARC Jul. 16, 2009 19 Super-K ND 280 Muon monitor Beam dump TS Main Ring RCS LINAC

Near detectors (ND 280) 20 Measure n beam energy spectrum, flux, flavor and interaction xsec before the n oscillation. Fine Grain Detectors (FGDs) measure neutrino vertices. Scintillator bars (FGD 1), scintillator bars + water (FGD 2) TPCs measure pm to reconstruct En spectrum and d. E/dx for particle ID. Micro. Megas w/ Ar/i. C 4 H 10/CF 4 (95/2/3) gas mixture Side Muon Range Detector (SMRD) measures the range of m. Scintillator planes btw the yokes p 0 detector (P 0 D) measures the rate of NC-p 0 production. TPCs FGDs UA 1 magnet ECALs yoke & SMRD Magnet coils Scintillator bars + lead foil/water T P 0 D Scintillator bars + lead foil Extrapolate the n energy spectrum and flux to Super-K. 3. 5 m 7. 0 m 3. 6 m ECALs measure electrons from FGD and g-rays from p 0. 2

1 st neutrino event in ND 280 21 07: 40 JST, Dec. 19, 2009 Magnet off P 0 D (TPC 1) TPC 2 FGD 1 TPC 3 FGD 2 DSECAL n beam TPC 1 was not taking data Interaction inside P 0 D, with tracks through all central detectors.

Super-KAMIOKANDE detector 50 -kton water Cherenkov detector (fiducial volume: 22. 5 kt). ~11, 000 20 -inch PMTs (inner detector). Good e-like (shower ring) / μ-like separation. CC-QE mis-PID probability: ~1% s. E ~ 80 Me. V (~10%) limited by Fermi motion, δEscale ~ 2%. New electronics & DAQ has been stably running since summer 2008. Improvement of decay-e tagging efficiency. Real-time transfer of T 2 K beam spill information. → Trigger of T 2 K event. CC-QE Inelastic s ~ 80 Me. V 22

Sensitivity to Dm 23 and q 23 23 30 Ge. V, 8. 3 x 1021 POT M. Diwan, Venice, Mar. 2009 d(sin 22 q 23) ≈ 0. 01, d(Dm 232) < 10– 4 e. V 2

Counts / 100 Me. V Sensitivity to Dm 23 and q 23 24 100 k. W x 107 sec Null oscillation case Oscillation case sin 22 q 23 = 1. 0 Dm 232 = 2. 4 x 10– 3 e. V 2 Enrec (Ge. V) d(sin 22 q 23) ≈ 0. 1, d(Dm 232) ≈ 4 x 10– 4 e. V 2 (90% CL) (Statistical error only)

T 2 K sensitivity to q 13 CHOOZ excluded > 10 times 0. 0060 @ Dm 232 = 2. 4 x 10– 3 e. V 2 (for a 10% sys. error) 25 30 Ge. V, 8. 3 x 1021 POT d. CP = 0

T 2 K sensitivity to q 13 26 30 Ge. V, 8. 3 x 1021 POT Dm 232 = 2. 4 x 10– 3 e. V 2

T 2 K sensitivity to q 13 27 100 k. W x 107 sec

Seek for the neutrino CP-violation 29 Atmospheric CP-violating CPV Interference CP-conserving Solar GF: Fermi coupling constant Ne: electron number density For nm ne, d –d and x –x. P(nm ne) ≠ P(nm ne).