Jun. 8, 2004
KEK-PS review

Neutrino experiment at J-PARC

T2K

Tokai-to-Kamioka long baseline neutrino experiment
Takashi Kobayashi
Institute for Particle and Nuclear Studies (IPNS)High Energy Accelerator Research Organization (KEK)

Contents
1. Introduction
2. T2K experiment
3. Physics Sensitivities
4. Possible future extensions
5. Current status of preparation
6. Summary
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

1Introduction• Evidences of ν oscillation in atm ν & {solar ν +reactor ν}– Finite masses– Large mixings!

• Still many mysteries in neutrino physics– Why so light?
– Why so differently mix from quark sector?
– How many (sterile) neutrinos?
– Absolute mass?/ hierarchy?
– Majorana? Dirac?
– CPV?

• Understanding properties of neutrino will provide clue towardphysics beyond the standard model– GUT (Seesaw model,..)– Leptogenesis– Extra dimensions.…

• Full exploration of whole structure of neutrino masses andmixing is a critical step
T.Kobayashi (KEK)

KEK-PS ReviewJun. 8, 2004

2

Neutrino mixing
If neutrino have finite mass, weak and mass eigenstates can differν l = ΣU li ν i
Weakmi: 3 masses, ∆mij: 2 differences

Mass eigenstates

Maki-Nakagawa-Sakata Matrix sij=sinθij, cij=cosθij U e1 U e 2 U e 3  3 mixing angles and 1 CPV phaseU = U µ1 U µ 2 U µ 3 Unknown 2 parametersU τ 1 Uτ 2 Uτ 3 00   1 0 0   c13 0 s13  c12 s12 0   1
   =  − s12 c12 0  ⋅  0 c23 s23  ⋅  0 1 0  ⋅  01 0
 0 0 − s  0 0 e − iδ   − s
01c2323     13 0 c13 

sin22θ12∼0.8(Solar)
T.Kobayashi (KEK)sin22θ23~1Reactor(Atm ν)Long baseline
experiments
KEK-PS Review
Jun. 8, 20043

What can be measured in LBL exp.
Oscillation probabilities2∆m122 << ∆m23
≈ ∆m132 = ∆matm

m3∆matm2
m2
m12∆mij2 = m 2j − mi2¾νµ disappearance: θ23
Pνµ → νµ≈ 1 − cos θ ⋅ sin 2θ ⋅ sin (1 . 27 ∆ m4

2132223atm~1L / Eν)Same¾ νe appearance: θ13(2Pνµ → ν e ≈ sin 2 θ 23 ⋅ sin 2 2 θ 13 ⋅ sin 2 1 . 27 ∆ m atm L / E ν~0.5¾ δ: CP in νe appearance)

sin22θµe2∆m12
sin 2θ12⋅ sin δA CP =≈⋅P(ν µ → ν e ) + P(ν µ → ν e ) 4Eν sin θ13

P( ν µ → ν e ) − P( ν µ → ν e )T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

4Current knowledge of ∆m232, θ23 and θ13
θ13

θ23-1

10

K2K(90%CL)∆m2 (eV2)-2

10K2K(‘02)

-3

10SK
FC+PC+up-µSK atm.ν
allowed (90%CL) CHOOZ(90%CL)-4
1000.1

0.2

0.3

0.4

0.5

sin22θµe~0.5sin22θ13
Small!! Only upper limit
T.Kobayashi (KEK)

KEK-PS Review

Nearly maxmal!
Jun. 8, 2004

5

Next goals of LBL experiments• Establish framework of 3 flavor mixing (or findsomething new)
– Discovery of νe appearance (θ13>0?)• At the same ∆m2 as νµ disapp. ÆFirm evidence of 3gen. mix.
• Open possibility to search for CPV (θany=0 Æ No CPV)

– Precision measurements of ocs. params.
• Really sin22θ23=1?? (disappearance)• Test exotic models (decay, extra dimensions,….)– Confirmation of νµÆντ• NC measurement• Sign of ∆m2• Search for CPV in lepton sector– Give hint on Matter/Anti-matter asymmetry in the universe
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

6

“T2K” (Tokai-to-Kamioka)
neutrino experiment
LOI: http://neutrino.kek.jp/jhfnu

νµ beam of ~1GeV
Super-K: 50 kton
Water Cherenkov

KamiokaJAERI(Tokai-mura)
0.75 MW 50 GeV PS~Mt “HyperKamiokande”

4MW 50GeV PS

Approved exp (x102 of K2K)zνµ→ νx disappearancezνµ→ νe appearancezNC measurement
T.Kobayashi (KEK)

Future Extension
zCP violation
z proton decay

KEK-PS Review

Jun. 8, 2004

7

Mile stones in the past
• 1999.4 : JHFν working group formed(ICRR/KEK/Kyoto/Kobe/Tohoku/TRIUMF)• 2001.4: Neutrino Facility Const. G. formed officially inKEK• 2002.12 : LOI submitted to J-PARC office• 2003.5 :International collaboration formed(Spokesperson: K.Nishikawa)• 2003.12: J-PARC NEUTRINO FACILITY APPROVED.
– 5 years budget(Apr.2004 ~ Mar.2009)– Total of 16.0Byen (~160M$)• 2004.4: Neutrino beam construction started!!
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

8WW International Collaboration
Country/Institute

1.Japan（9inst's）

1 ICRR, U. Tokyo
2 KEK
3 Tohoku U.
4 Hiroshima U.
5 Kyoto U.
6 Kobe U.
7 Osaka City U.
8 U. Tokyo
9 Miyagi U. of Education

2.US（14inst's）

1 UCI
2 SUNY-SB
3 U. Rochester
4 U. Pennsylvania
5 Boston U.
6 CSU, Dominguez Hills
7 BNL
8 UCB/LBL
9 U. Hawaii
10 ANL11 MIT
12 LSU
13 LANL
14 U. Washington

3.Korea（8inst's）

1 Seoul National U.
2 Chonnam National U.
3 Dongshin U.
4 Kangwon U.
5 Kyungpook National U.
6 KyungSang National U.
7 SungKyunKwan U.
8 Yonsei U.

T.Kobayashi (KEK)#ofcollabor
ators

45
13126
3
3
322
138
5
5
544
3
3
2
2
1
1
1
1
1102
2
1
1
1
1
11

4.Poland（1inst's）

1 Warsaw U.

5.Spain

1（2inst's）

1 U. Barcelona
2 U. Valencia

6.Switzerland（1inst's）

22（1inst's）

4（4inst's）

7

1 INR

48.Italy
1 U. Roma
2 U. Bari
3 U. Napoli
4 U. Padova

9.France3211（1inst's）

5（6inst's）

20

1 CEA Saclay

10.Canada

5

1 TRIUMF
2 U. Alberta
3 York U.
4 U. Toronto
5 U. Victoria
6 U. Regina

11.China1232
111（1inst's）

1 IHEP(Inst. Of High Energy Phys.)12.UK（4inst's）

1 RAL
2 Imperial College London
3 Queen Mary Westfield College London
4 U. Liverpool

••
••

523

1 U. Geneva

7.Russia

1447
1213Formed in May 200312 countries, 52 institutions
148 collaborators (not incl. students)
Spokesperson: K.Nishikawa (Kyoto U.)

KEK-PS Review

Jun. 8, 2004

9

Neutrino facility in J-PARC“Conventional” beamp+X Æ π+ + X’
νµ+µ+Components¾ Primary proton beam line
¾ Normal conducting magnets¾ Superconducting arc¾ Proton beam monitors¾ Target/Horn system¾ Decay pipe (130m)¾ Cover OA angle 2~3 deg.

¾ Beam dump
¾ muon monitors¾ Near neutrino detector @ 280m from trg.
¾ Medium detector (@~2km) not approved yet
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

10Off-axis beam

Far Det.

(ref.: BNL-E889 Proposal)
Horns Decay Pipe

θTargetDecay Kinematics
Eν2Eν =mπ − mµ22( Eπ − pπ cosθ )θ=0°
θ=1.0°

1

θ=2.0°

05Osc. Prob.=sin2(1.27∆m2L/Eν)osc.max.

WBB w/ intentionally misaligned
beam line from det. axis

∆m2=3x10-3eV2
L=295km

νµ~2°

OA1°
OA2°
OA3°

Eπ～3000 CC int./22.5kt/yr
νe: 1.0% (0.2% @ peak);
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

Eν11

Detector complex
Not approved!

pπ0m

ν

140m

280m

2 km

• Muon monitors @ ~140m– Fast (spill-by-spill)monitoring of beam
direction/intensity• First Front detector @280m– Intensity, Direction,Spectrum, ν interaction• Second Front Detector @~2km (not approved)• Far detector @ 295km– Super-Kamiokande(50kt)
T.Kobayashi (KEK)
KEK-PS Review

295 kmNeutrino spectra at diff. distx 10 31.5km

1800

1600

1400

295km

1200

1000

800

600

0.28km

400

200

000.5

11.522.5

33.5

44.55Eν (GeV)

dominant
syst. in K2K
Jun. 8, 2004

12Concept of Near Neutrino Detector• Off-axis (~2o)

Neutron shield– νµ and νe neutrino
fluxes and thespectra.
– ν interaction study(CC-QE, non-QE,π0, )– KaonContributions

16m
SKSK direction
FGDMRD

36m

Grid µ profile

Extruded Scintillator

2°– Beam direction
1m – Beam stability– (Spectrum)?

µIron~14m

lator
gh holes.)

1m

3m

3m

20mΦ
T.Kobayashi (KEK)• On-axis (0o)1ν beam5m
3°WaveKEK-PS Review

1m

The detector design
is just started
Jun. 8, 2004

13

（April 1996 commissioned）

Far detector: Super-Kamiokande

50,000 ton water Cherenkov detector (22.5 kton fiducial volume)

41.4m

Optically separated INNER and OUTER detector

40m
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

14

Eν reconstruction in water Cherenkov
Assume CC Quasi Elastic (QE) reactionl (µ, e)νµ + n → l + pνπ(El , pl)Eν =mN Eµ − mµ2 2mN − Eµ + pµ cosθ µp
SK MCInelastic BG
σ~80MeV

ccQEccQE

cc-inelastic

T.Kobayashibeam(KEK) energyEν(reconstruct) – Eν (True) (MeV)KEK-PS Review

Jun. 8, 2004

15

nonQEw/o osc.

δ(∆m232 )# of events (arb. unit)

Fully contained ,1-ring, µ-likesampleδ(sin22θ23)

Measurement of sin22θ23 , ∆m223
νµ disappearance

OAB-3oOAB-2o∆m2 = 3.0 x 10-3 eV2True ∆m232 (eV2)

T.Kobayashi (KEK)

KEK-PS Review

δ(sin22θ)~0.012) ~<1×10-4δ(∆mJun. 8, 200416

sin22θ13 from νe appearance
Off axis 2 deg, 5 years∆m2CHOOZ excluded

at35

Expected
Signal+BG
2sin 2θ13=0.10
sin22θ23=1.0∆m2=0.003eV230Total BG

25

BG from νµ+antiνµ20

Off axis 2 deg, 5 years

15

114.6 signal/ 24.9 BG

10Sin22θ

513>0.0060sin22θ

00.5

113

1.5

2

2.5 3 3.5 4 4.5 5
Reconstructed Eν(GeV)

2-ring merged to 1-ring

γSignalνe + n → e + p(Eµ , pµ)νT.Kobayashi (KEK)

KEK-PS ReviewBG
beam νeπ0π0γ

Jun. 8, 2004

17

Future Extension: Search for CPV2sin 2θ13

JHF-HK CPV Sensitivity
CHOOZ excluded
sin22θ13<0.12@∆m312~3x10-3eV20.14
0.120.1

4MW, 540kt
2yr for νµ6~7yr for νµstat+5%syst.

stat+2%syst.
0.08(signal+BG) stat only
0.06

stat+10%syst.

no BG
0.04
signal stat only
0.02
00T2K 3σ discovery

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1sinδ

3σ CP sensitivity : |δ|>20o for sin22θ13>0.01 with 2% syst.
T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 200418Design and development statusof beam line components

T.Kobayashi (KEK)

KEK-PS Review

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19

Superconducting combined functionmagnet• Both D and Q field in 1 magnet• Reduce cost (40Æ28mags) comp. w/ sep.
func. FODO.
• Larger acceptance• First application in the world•Current：~7000A•Dipole field ：2.6T x 3.3m
•Quadrupole：18.6T/m•Precision: 10-3@5cm•Total 28 mags(14cell)•Quench margin ~70%

T.Kobayashi (KEK)

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Development of Superconducting magnets
Trial coil winding (Dec.2003~)

Trial magnet (Feb.2004)(Plastic collar, Iron yoke)

Cryo.Sci.C. KEK

Schedule• Prototype Test Jun.04• Mass production from 2005
T.Kobayashi (KEK)

KEK-PS Review

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21

Target:Graphite 3cmf x 90cm
Issues• Thermal stress

Target R&D

Hayato, Nakadaira, Ichikawa, ..
Target&Monitor G.(Noumi)

Example of FEM (by T.Nakadaira)

Water cooling– Max. stress 6.8MPa, Safety fact. 3~4
available.

•Cooling– Water or He gas cooling– T=~240deg(~700deg) w/ water(He) cooling.
– 20kW can be removed by direct water cooling••

Radiation effect (size shrink, thermal
conductivity decreases)
And so on,..
Target in water pipe

Helium cooling600~700ºC@center

500ºC@surface

T.Kobayashi (KEK)

KEK-PS Review

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22

Horn system
900472
1400

809
1400

Targetbeam

2000

1st Horn 2nd Horn

2500

100 cm

3rd Hornx 103• Conceptual design (fieldshape optimization) done.
(Ichikawa)• 3 horn system• 320kA pulse current• Water cooled inside• Under engineering design
T.Kobayashi (KEK)

KEK-PS Review

OAB 0.0deg

3000

Perfect horn(accept. 180º)

2500
2000

T2K horn

1500
1000
500001234Jun. 8, 2004

5678

9 10(GeV/c) 23
Eν (GeV)Prototype of 1st horn inner conductor• Preparing fullcurrent (320kA)
operation testusing K2K outerconductor
T.Kobayashi (KEK)Yamanoi,Ichikawa
KEK-PS Review

Jun. 8, 200424

Decay volume

Sakuda3NBT (BT between 3GeV&MLF)
50m under 3NBT will be
constructed in 2004

TargetStation~15m

OA2o
OA3o
Decay Volume ~110m• Cover OAB 2~3deg.

Dump~10m

He vessel wall equipped w/ water piping– Peak Eν ~ 500-800MeV• Helium filled to reduce absorption.
• Water-cooled He vessel insideconcrete shield• 71.4m part of vessel purchased.
• Start construction of crossing part:June 2004

T.Kobayashi (KEK)

KEK-PS Review

Jun. 8, 2004

25

Summary• J-PARC neutrino facility approved!
– 5 years construction (JFY2004~2008)• Expected neutrino beam
– ~3000 CC int./yr @ SK (w/o osc.)– ~0.2% νe contamination• Physics sensitivity of T2K experiment– sin2θ13≤0.006 (90%CL)δ(∆m2)≲3%, δ(sin2θ23)~1%– Could be sensitive to CPV of δ≳20o in the future• Design and R&D of beam line components
are going• First neutrino beam planned in 2009
T.Kobayashi (KEK)

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Jun. 8, 200427