NEAR DETECTOR

DECAY VOLUMETARGET STATION

SUPER-COND. MAGNETSDUMP/MUON MONITOR

10-4

10-3

10-2

10-1

10 -3 10-2 10 -1 1sin22θ13

∆m

2(e

V2

)

Expected 90% sensitivity contour on (∆m132, sin22θ13)

compared with the CHOOZ exclusion plot.

The sensitivities to sin22θ23 and ∆m232

as a function of true ∆m232.

δθ

sin

22

OA2˚

∆m2

10

1

0.002 0.004 0.006 0.002 0.004 0.006

-1

10-2

10-3

10-4

δ∆m

2(e

V2

)

(eV2)∆m2(eV2)

OA3˚

OA2˚

OA3˚

OAB 2degree (5years)

CHOOZ excluted

3 GeV SynchrotronV Synchr

500 GeV SynchrotronGeV Synchrotr

295295kmkmFuture PlanFuture Plan

K2K K2K

250250kmkm

KEK

295kmK2K Current Experiment

Current ExperimentCurrent Experiment250km

Future PlanTOKAIKAMIOKA

A KEK-beam produced Super-Kamiokande event

0

2

4

6

8

10

12

0 1 2 3 4 5

E ν rec

Even

ts

10-4

10-3

10-2

0 0.2 0.4 0.6 0.8 1

sin22θµe

sin22θµe

∆m

2(e

V2)

∆m

2(e

V2)

10-4

10-3

10-2

10-1

0 0.1 0.2 0.3 0.4 0.5

K2K(90%CL)K %

CHOOZ(90%CL)O %

SK atm..allowed (90%CL)d L

K2K-I oscillation analysis plots

(a) Reconstructed Eν distribution for the single ring muon-like samples, overlayed with various MC expectations.

(b) Allowed regions of oscillation parameters in νµ disappearance mode. The best fit point is indicated by the star.

(c) Excluded region of oscillation parameters in νe appearance mode, in comparison with results of the other experiments.

Best fitwith oscillation

Without oscillation(entry normalization)

Normalized to theexpected numberof events (44)

1σ90%C.L.99%C.L.

(a) (b)

(c) Bird's-eye view of the neutrino beam-line at KEK. It provides a 98% purewide-band <Eν>=1.3 GeV muon neutrino beam from the KEK 12 GeV PS.

A near detector system is located 300 m downstream from the target.

Installation of a new near detector module, Sci-Bar,is taking place since January 2003.

J-PARC, Japan Proton Accerelator Research Complex.Neutrino beamline facilities will be constructed at 50 GeV Proton Synchrotron (PS),

which will provide a beam ~100 times more intense than KEK-PS.

Intermediate neutrino detector at 2 km from target

Super-Kamiokande after its recoveryfrom the accident (ICRR, Univ.of Tokyo, 2002/09).

KS probability = 64.3%

1018 POT

even

ts

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60

1999 ~ 2001 2003K2K-I K2K-II

Number of observed events at SKvs number of protons on target (POT).

56 K2K-I events + 16 K2K-II events are plotted.Blue line is averaged rate (1.14 events / 1018 POT).

PPP

111222 GeV PSGeV PSGeV PS

NGNGNGNGGGGGNNNNNNNNGGGGRINRINRIRIRIRIIIRRRRB RB RB RB RKBKBKKBBBBKKKKKKKKEKEKEE NNNNBBBBEKEKEEKEKEKKKKKKKKKKKEKB RINGKEKB RINGKEKB RING

EastEastEastCounter HallCounter HallCounter Hall

NorthNorthNorthCounter HallCounter HallCounter Hall

Primary Beam -linePrimary Beam -linePrimary Beam -line

Muon PitMuon PitMuon Pit

Near DetectorsNear DetectorsNear Detectors

Dec

ay T

unne

l

Dec

ay T

unne

l

Dec

ay T

unne

l(2

00m

)(2

00m

)(2

00m

)

Target StationTarget StationTarget Station

A project involving a next-generation long baseline neutrino oscillation experiment connecting 295 km between J-PARC 50 GeV Proton Synchrotron and Super-Kamiokande is being proposed. It is designed to observe the first signal of νe appearance and to measure a finite θ13 value. A 2̊ ~3̊ off-axis (OA) neutrino beam is being considered. An intermediate neutrino detector will also be constructed at 2 km from the target. The possibility of measuring a CP violation effect using an anti-neutrino beam, after apparatus upgrades in the future, is also being discussed.

Next Generation Long-Baseline Neutrino Oscillation Experiment at J-PARC

Progress of K2K: New Analysis for Phase-I and Successful Start of Phase-II http://neutrino.kek.jp/

http://www-nu.kek.jp/jhfnu/

K2K, the first long-baseline neutrino oscillation experiment in operation, has collected one-half of its planned 1020 protons on target through July 2001 (K2K-I). We have collected 56 events in Super-Kamiokande, compared to the expectation, 80.1+6.2 . We use 29 single-ring muon like events to study the energy spectrum distortion. The probability that these results are caused by statistical fluctuation without neutrino oscillation is less than 1 %. A limit for νe appearance mode has been obtained: sin22θµe < 0.15 at ∆m2= 2.8x10-3 eV2 . The new phase of the experiment, K2K-II, which started after the recovery from the Super-Kamiokande accident, will provide sufficient statistics for further study on neutrino oscillation. As of April 21st, 16 more events have been obtained, compared to the expectation, 26.6+2.3 .-2.6

-5.4

KEKKEK K2K& Next Generation LongBaseline Experiment