T2K実験の現状
2010年2月9日
柴田政宏 (KEK)
For the T2K collaboration

Outline
1. Introduction
Motivation, setup, sensitivity of the T2K experiment● Neutrino facility and detectors●

2. Neutrino facility commissioning
3. Prospect of θ13 search
4. Summary2

1. Introduction

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Physics motivation●

To understand neutrino mixing●Discovery of finite θ13 through νe appearance–θ13≠0 → CP violation measurement in the future

Could be a hint to understand how matter dominateduniverse was madePrecise measurement of θ23 and Δm223 through νμdisappearance– θ23 is maximal mixing?
●●0ν e   1
  
 ν µ  =  0 cos θ 23
 ν   0 − sin θ23 τ  sin θ 23 cos θ 23 0 cos θ 130
 − sin θ e − iδ13

0 sin θ 13e − iδ 10
0cos θ 13  cos θ 12
 − sin θ 12
0
sin θ 12cos θ 1200  ν 1   0  ν 2 1   ν 3 4Tokai to Kamioka experiment (T2K)●Long base line (295 km) neutrino oscillation experiment with- high power (MW class) proton beam of J-PARC Main Ring
- world largest water Cherenkov neutrino detector (Super-Kamiokande)
5- off axis beam to achieve narrow energy band and low backgroundCollaboration of the T2K experiment~ 400 members from 12 Countries
Japan, US, Canada, France, UK,
Switzerland, Poland, Korea, Russia, Spain,Italy, Germany

6Setup of the T2K experiment

Off axis beam (2.5°)● Peak energy ~600MeV● Narrow energy spectrum● Expected event● 1700 CC-interaction/22.5kt/3000h(30GeV, 750kW, no oscillation)● νcontaminatione●●0.4% @ peak energy

7Neutrino energy reconstruction●●Interaction with nucleon in detector material is utilized.
Neutrino energy is derived from Charge Current Quasi Elastic
scattering (CCQE).
CCQE

CC-inelasticp

Neutral Current (NC)νe appearance●Signal●●e- from CCQE interaction

Background●●Intrinsic νe in νμ beam
π0 misidentification as e(from NC1π interaction)

Sensitivity of θ13

2222 1.27Δm 31 LP ν μ  ν e ≈sin 2θ13 sin 2θ23 sin
ECHOOZsin22θ13＜0.13(Δm2=2.8×10-3)@ 90% C.L.

sin22θ13 = 0.1# of events in 0.35~0.85 [GeV]
Signal … 143Beam νe BG … 16
BG from νµ … 10

T2K goalsin22θ13～0.006 @ 90% C.L.
(Δm2=2.4×10-3,10% sys. error)

CHOO

Z

ex
cluded8×1021 POT@30GeV
10Δm2=2.4×10-3,10% sys. error

2Sensitivity of θ23 and Δm 23

21.27Δm2
223 LP ν μ  ν μ ≈1−sin 2θ 23 sinECurrent value
sin22θ23 ＞ 0.92 @ 90% C.L. (SK)|Δm223| = 2.43±0.13×10-3 eV2@ 68% C.L. (MINOS)

T2K goalδ(sin22θ23)＜0.01
δ(Δm223)＜10-4eV2@ 90% C.L.


8×1021 POT@30GeV

δ(Δm223)＜10-4eV2
δ(sin22θ23)＜0.01(stat. error only)

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Neutrino facility
andNeutrino detectors

12181MeV Linac

J-PARC Facility(KEK/JAEA）
South to North

3 GeV RCS
(Rapid CyclingSynchrotron)

Neutrino Beams(to Kamioka)

Materials and Life
Experimental Facility
MR(MainRing)

CY2007 Beams
JFY2008 Beams
JFY2009 Beams

Slow Extraction
Exp. Facility13
Bird’s eye photo in January of 2008

Neutrino facility
HornNeutrino monitor building

to Kamioka

TargetπνpNear detector (ND280)

Primary proton beam line

Beam dump

Target station
Decay volume14

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Proton beam monitors
Intensity monitor: current transformer (CT)
Position monitor: electro static monitor (ESM)
Profile monitor:
segmented secondary emission monitor (SSEM)
optical transition radiation monitor (OTR)Beam loss monitor (BLM): ionization chamber


ESM

CTOTR

SSEM

BLM

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Muon monitor●●Muon monitor measuresdirection, profile and intensityof muons produced withneutrinos.
Muon monitor is an array ofion chambers and Si PIN
photodiodes installed
downstream of the beam
dump.

Chamber

Silicon16

Near detector (ND280)
Off axis detector
On axis detector● measure direction andintensity of neutrino beam
● Off axis detector● measure flux and energy
spectrum of neutrino beam
● measure ν contaminatione●●measure cross section ofneutrino-nucleon interaction

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On axis detector

On axis detector (INGRID)
16 modules cover 10m×10mregion.
●10m

Each module consists of 9iron targets, 11 scintillator
planes and veto planes.
●10mThe scintillator planeconsists of scintillator, WLS
fiber and MPPC.
●

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Off axis detector
P0D●High statistics π0 measurement● Tracker (TPC + FGD)
● Charged particle tracking●FGD also measures π0●ECAL●Measure π0 with P0D and FGD● Photon veto
● SMRD● Measure range of muons● Veto from outside●Downstream
ECAL

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Far detector (Super-Kamiokande)●

50 kt water Cherenkov detector
with 13,031 photo-multipliers(fiducial volume: 22.5 kt)●New electronics installed insummer of 2008 (SK-IV)
Stable and dead time less DAQ●
Wide charge dynamic range
DAQ has been stable and detector
calibrations have been performed●●●

SK is ready for T2K physics run

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Far detector (Super-Kamiokande)e from μ decay●

50 kt water Cherenkov detector
with 13,031 photo-multipliers(fiducial volume: 22.5 kt)●

no dead time

New electronics installed insummer of 2008 (SK-IV)
Stable and dead time less DAQ●
Wide charge dynamic range
DAQ has been stable and detector
calibrations have been performed●●~1000p.e.
●atm-ν event

SK is ready for T2K physics run

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2. Neutrino facility commissioning22

First year of the T2K experiment●April Commissioning started
First neutrino production●MayCommissioning●June~October●NovemberCommissioning resumed
First event in INGRID
Off axis detector became ready for beam

●DecemberCommissioning
First event in off axis detector

Summer shutdown
Horn2, 3 installed
All INGRID modules installed

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First beam commissioning
2009.4.23

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First beam commissioning
2009.4.23 (first shot)
Proton profile monitor(SSEM)

Muon monitor

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First neutrino event in INGRID

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First neutrino event in INGRID

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First neutrino event in off axis detector

ν beamNot operated

Not fully operated

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Achievements of commissioning(by the end of 2009)●

Basic functionality of beam monitors was confirmed.

●

Near detector observed neutrino events.

●

Proton beam orbit was tuned within 2mm. No significant beamloss was observed.

●

Integrated proton number: 3.9×1016 (20 days operation)●

Max. power: 20kW (continuous), 50kW (one shot operation)●●Beam stability was checked through 30 min. continuous
operation.
(intensity < 1%, position @ most downstream < 0.2mm,direction @ mumon < 1mrad, beam width @ target < 9%)Focusing effect of the electromagnetic horns was confirmed.
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Orbit tuning of proton beamline●No significant beam loss was observed.

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Integrated proton number & max. intensity

50kW

20kW
10kW

Integrated proton number: 3.92±0.04×1016● Max. intensity: 20kW (continuous), 50kW (single shot)●

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Focusing effect of horn×7.1×2.1

SiICPreliminary

Preliminary

Current [kA] Peak [pC]Sigma [cm]Current [kA] Peak [pC]

Sigma [cm]3201551

82

320

38.5

90250467

95

250

13.2

103021910906.312532

3. Prospect of θ13 search●●Aiming to search θ13 withbetter sensitivity than CHOOZ
using data of 2010 physics run
with 100kW × 107 s operation.
The goal is to discover θ13 with
3.75MW × 107 s physics run.
(3.75MW × 107 s = 8×1021
POT@30GeV)

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4. Summary●●

T2K is an accelerator based long base line neutrino oscillation
experiment aiming to conclude neutrino mixing.
●Discovery of νe appearance●

Precise measurement of νμ disappearance

Neutrino facility started operation from April 2009.
Functionality of the facility was confirmed.
●
Neutrino events were observed in the near detector.
Preparation for physics run is progressing.
●

●

●

●

We aim to start data taking from March of 2010 and search θ13with sensitivity better than CHOOZ in 2010.
Our goal is discovery of θ13 with 3.75MW×107s physics run.

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