1. J-PARC neutrino experiment (T2K) and future
Takasumi Maruyama (KEK)
On behalf of T2K collaboration
and
LAr R&D group

2. Particles and interactions
Strong interaction
Particles which make material
Intermediate particles u c t g
Electro-magnetic
interaction
Quarks; make nucleon (nuclear) γ d s b νe νμ ντ W+ W- Z
Lepton; company of electron e μ τ
Weak
interaction H ? ?
Particles which
gives mass
Higgs particle(s)

3. Particles and interactions
Strong interaction
Particles which make material
Intermediate particles u c t g
Electro-magnetic
interaction
Quarks; make nucleon (nuclear) γ d s b νe νμ ντ W+ W- Z
Lepton; company of electron e μ τ
Weak
interaction H ? ?
Particles which
gives mass
Higgs particle(s)

4. Neutrino Oscillationsνμ ντ
Neutrino Oscillations
Happens only if neutrinos have ”mass” (once no one believed
there is mass. I.e. standard model had no mass.)
Oscillate to other neutrino generations
Oscillation probability is based on the ”energy” and ”distance”
Accelerator neutrino is dominated by nm (except for a few %)
nm – nt and nm – ne oscillations has been well studied during this
12 years, but not well studied nt – ne oscillation
nt – ne oscillation could provide hints of asymmetry between
matter and anti-matter in our universe.

5. J-PARC and T2K experiment
T2K experiment (starts from April-2009)
J-PARC accelerator and neutrino beam-line makes nm beam
directed to super-Kamiokande which is apart from Tokai by 295km.
Super-Kamiokande can study how to oscillate neutrinos, especially
nm – ne oscillation. (nm – nt – ne oscillation gives the first and third
generation oscillation probability)
If there is large oscillation, it opens the way to search for matter
dominant universe.

6. J-PARC Slow Extracted Beam Facility Materials and Life Science
Experimental Facility
Hadron Beam Facility
Neutrino to Kamiokande
Nuclear Transmutation
Main Ring
(30 GeV, 0.3 Hz,
0.75 MW→ 1.66 MW)
Linac
180→400 MeV
Rapid Cycling Synchrotron
(3GeV, 25 Hz, 1MW)
J-PARC = Japan Proton Accelerator Research Complex
Joint Project between KEK and JAEA

7. Neutrino Oscillation Experimentalists determine;
Disappearance measurement
Flux w/o
oscillation
Experimentalists determine;
Neutrino Energy En (GeV) , travel distance L(km)
Measurement parameter;
Oscillation amplitude q23, delta m squared Dm232 q
Survival probability
Dm232
Compare energy
spectrum between
w/ and w/o
oscillation 2
Neutrino Energy En (GeV)
Appearance of electron neutrinos provide unmeasured mixing angle q13 and hints for matter-antimatter asymmetry.

8. How to make neutrino beam　(Bend accelerated 30GeV protons and hit them to target. Pions are made around target are focused with magnetic horns)
Building for neutrino monitor
Magnetic horns (3horns)
target
p+p->X+π
Stop all charged
particles w/ absorber
and soil.
protons
π-> μ＋ν
UA1 magnet donated
From CERN installed
Bend protons from acc. to target
Absorber for
charged particles
Target station 8
Pions decay volume

9. T2K Physics Run begins in 2010 (until June)
~100kW
~50kW
 Beam Power
Delivered POT: 3.35×1019 (3.28×1019 for physics)
Continuous ~50kW level
Trial up to 100kW successful.

10. Off-axis detectors inside UA1 magnet
T2K-ND280 detector system
On-axis detector
“INGRID”
Off-axis detectors inside UA1 magnet
We will visit here!! (this afternoon)
some of you will see neutrino events here on 16-Feb.

11. Near detectors
Near detectors are set inside Tokai in order to measure the neutrino properties (energy, rate,) before oscillation.
For disappearance, nm rate and energy measurements are important.
For appearance, ne rate and energy meas. are crucial.
First on-axis detector
(INGRID) event.

12. Near Detector Neutrino Measurements
dE/dx by TPC (positive)
Neutrino interaction
proton
electron
MIP (m/p)
ICHEP talk by Flor de Maria Blaszczyk
Neutrino event rate
( INGRID)
Neutrino event timing
( INGRID)
June 26th
Jan. 23rd
ICHEP T.Nakaya (Kyoto) --

13. 40m diameter, 40m height 50kt water is contained.
Super Kamiokande
50,000ton
Water Cherenkov
40m diameter, 40m height
50kt water is contained.
~10000PMTs, 40% photo-
coverage.
Cherenkov
Charged
particle

14. Electron-like and muon-like events
e-like
m-like e m

15. First T2K event candidate in Super-Kamiokande
First physics result (w/ 3.1x1019 POT) will come soon!!
Continuous operation provided > 1x1020 POT (proton on target) recently. (achieved ~135kW)

16. Super-K(Far detector) neutrino events
LE: Low energy triggered events
OD: Outer detector events
FC: Fully contained events FC OD LE FC
Clean beam timing structure confirmed in FC events
Twenty-two FC events observed by Mid. May in 2010
Non-beam BG estimated to be <10-3evts

17. Accelerator experiment
Neutrinos can be measured more than once
Relative change of rate and spectrum
Effect of oscillation depend only on neutrino energy (fixed distance)
Beam energy can be chosen
Type of detector
Neutrino energy determination method can be chosen

18. A next-generation experiment
Build 100kt level liquid Argon detector .
For example, one good site candidate is Okinoshima to build. It is apart from Tokai by 658km away.
We need to (upgraded) intense neutrino beam as well.
This kind of long
base-line might provide
good hints for neutrino
CP violation term.
(matter and anti-matter
asymmetry term)
Okinoshima
From Tokai
~658km
A.Bueno et al

19. u c d s t b νe νμ ντ e μ τ u c d s t b νe νμ ντ e μ τ
Asymmetry between matter and antimatter ~ CP violation in lepton sector~ u c d s t b νe νμ ντ e μ τ
matter
Lepton; company of electrons
Quark; company makes nucleons u c d s t b νe νμ ντ e μ τ
Antimatter
(anti-leptons)
(anti-quarks)
Particles (matter) and Anti-particles (anti-matter)
Particles must have their anti-particles. (normally, they have opposite charges)
If there are same physics between quarks and anti-quarks, there should same amount of the matter and anti-matter in our universe. (but anti-matter is quite small)
　If there is different property between neutrinos and anti-neutrinos, it could explain the matter dominant universe, which is made in earlier universe age. By the way, famous quark/anti-quark asymmetry (Kobayashi-Maskawa) cannot cover all.

20. ne  nm oscillation probability
dcp provides diff
between n and
anti-n
To see d
　meas. n and
anti-n diff.
or.
　meas. n energy
spectrum
Interference term
plays important
role!!
A.Bueno et al
NP08 on Mar

21. nm  ne oscillation probability (on E/L)
dCP=0
dCP=90
dCP=270
Oscillation probability
Dm312 = 2.5x10-3 eV2
sin22q13 = 0.1
No matter effects
1st Oscillation
Maximum
E/L~1.27Dm2*2/p
(E/L)
2nd Oscillation
Maximum
E/L~1.27Dm2*2/3p
Oscillation
Minimum
E/L~1.27Dm2/p
A.Bueno et al
NP08 on Mar

22. Why liquid Argon detector?
Revival “bubble chamber” with latest technology
Tracking detector:
Measure precise event topology
Can measure low momentum particles.
Can measure local dE/dx
PID with dE/dx and track length (range)
Distinguish electron from pi-zero. (eff %, while rejection factor is 1000)
Full sampling, wide solid angle (4p), same material
Good energy resolution
65 cm e-
50 cm p
MC νe CC, Eν=0.730 GeV
240 cm p μ-
90 cm
MC single π0, E=0.5 GeV
MC νμ CC, Eν=1.73 GeV
One of the best detectors which has good performance for neutrino phys.

23. Spectra for ne CC events45
Shaded is beam ne background, while histogram shows the osc’d signal.
dcp effects are seen in 1st and 2nd osc. Maxima.
(perfect resolution case) 25
0 deg
90 deg 4 4 60 40
180 deg
270 deg
A.Bueno et al 4
NP08 on Mar 4

24. Allowed regions This is perfect energy spectrum case
Cases at dcp=0,90,180,270 and sin22q13=0.1,0.05,0.03 are overlaid.
Each point has 67,95,99.7% C.L contours
Perfect resolution case
A.Bueno et al
NP08 on Mar

25. Image of ~100kt LAr and important R&D components
Liquid phase
Single stage GEM
Readout
Gas phase
Test for long drift distance of ionized electrons using cylindrical cryostat
Double phase detector readout using both liquid and gas Argon phases (with GEM/LEM)
Electronic
racks
Charge readout plane
GasAr
E ≈ 3 kV/cm
Extraction grid
E-field
LAr
20m
E≈ 1 kV/cm
Field shaping
electrodes
80m
　Very high purity of LAr is needed. (t(ms)=300/ppb,
e.g: 1/e at ~5cm of 10ppb with 1kV/cm)
Drift velocity is slower with lower voltage,
and it affects more attenuation in LAr.
　To provide better S/N, GAr is used, too.
Cathode (- HV)
High Voltage up to ~MV

26. Concept of the LAr TPC Ionization selectron signal ~5x104e/cm MIP
Liquid Ar
1 kV/cm
Gas Argon
5kV/cm
GEM
readout
Ionization selectron signal
~5x104e/cm MIP
3D track reconstruction as a TPC
drift velocity is ~mm/μs with ~kV/cm electric field
LAr purity affects the attenuation of the drift electrons.
No amplification inside LAr
Diffusion of the drift electrons is
about 3mm after 20m drift
Double phase
Ionization electrons
Scintillation light
Cherenkov light
Charged particle
Electric
Field
nm charged current event
ドリフト速度:
P10 50 mm/micros
純Ar: 1-5 mm/micros
ne charged current event
A. Bueno, et.al.,, hep-ph/

27. Strategy toward huge detector (Japan)
250L detector
100 cm
40 cm
　We prepare for several steps toward 100kt
10L (test of double phase readout) -> under testing
250L (test for charged particles’ (mainly K) response of LAr TPC at J-PARC) -> We achieved in 2010 fall
ton detector -> under discussion
40~1000ton
detector
　Until 250L, we achieved to operate the detector.
20 m
80 m
100ｋｔ detector

28. Purpose of 250L Test-beam with well-defined charged particles
Test of the detector response.
Using J-PARC K1.1BR beamline on October 2010 to understand the K+ response mainly (with proton decay momentum region).
Test of double phase detector with the size of ~0.4m x 0.8m readout.
to optimize the detector for neutrino/proton decay physics. (gain of LEM, ~10, is enough, i.e. easier than dark matter search.)

29. Slow Extraction Exp. Facility Materials and Life Experimental Facility
J-PARC Accelerator
and Experimental
Facility
3 GeV Synchrotron
Linac
South to North
MR (Main Ring Synchrotron) 30GeV 0.75MW
Slow Extraction Exp. Facility
Materials and Life Experimental Facility
Neutrino Beams　(to Kamioka)
以上、加速器の現状を述べましたが、それでは，この施設を用いてどんな研究を展開するのかという話題に移りたいと思います。
この写真はさっきの写真とよく似ておりますが、実験室がよく見えるように、逆方向の南から北方向を眺めたものです。
本年度末には、物質生命科学実験施設とハドロン実験施設において実験が始まります。そして、来年度早々には、ニュートリノビームを神岡の方に送ることにしております。
実験室としては３つありますので、それぞれでどんな科学が展開されるのかをザッと眺めたいと思います。
Bird’s eye photo in January of 2008

30. Hadron Hall
Brand-new
K1.1BR
beamline
LAr
250L

31. Beam counter layout (PID)
0.8GeV/c K/p ratio (max.) ~ 1/4
a few K+/spill(=6s) (max.)
beam profile
s(x)~8cm, s(y)~6cm
Degrader (Lead Glass)
Beam
Hodoscope
MWPC2
MWPC1
TOF2
Gas
Cherenkov
TOF1
BDC
Fitch
Cherenkov
K, p beam
BDC = Beam defining counter

32. Event display (GEANT4) K+ from proton decay events has ~350MeV/c
Range is ~15cm in LAr. -> we can measure properties well.
Secondary particles from K+ was not fully contained, but can be used for the analysis.
K -> μ + n
TPC
K+ -> e+ + n + p0
TPC
K+ -> m + n (BR; 63.5%)
K+ -> p+ + p0 (BR; 20.7%)
K+ -> p0 + e+ + ne (BR: 5.1%)

33. PID performance using dE/dx info.
Top: dE/dx in each pitch (K, p, m) as a function of the distance from the particle stopped point.
Bottom; Likelihood distributions of K, p and m using probability density function of dE/dx in each pitch (top). Good separation, but tails have to be checked.
Kaon
Kaon
Pion
Pion
Muon
Muon
Kaon
Pion
Muon
Likelihood using dE/dX

34. Setup of Oct-2010 test-beam
Fiducial mass
170kg
Total LAr mass
~400kg
Field cage dimension
42cm x 42cm x 78cm
Fiducial volume
40cm x 40cm x 76cm
Typical Drift Field
~225V / cm
Maximum drift voltage
12kV (same feed-through as 10L)
Readout method
single phase (temporary)
Number of readout channels
76 strips (1cm)
drift
PMT
Double phase component is under production at CERN. (Unfortunately, not in time for test-beam.)
76 strips (1cm) anode

35. Charged particle test-beam
@J-PARC (Oct/23-31)
View from cathode side
(see 1cm strip anode at far side)

36. The “text-book” event (=cm) pion positron proton ~40cm
All are 0.8GeV/c
PID by local dE/dx and range (even by eye)
(=cm)

37. Event gallery ~600 MeV/c K+ (800+degrader) 200MeV/c pion
800MeV/c proton
800MeV/c positron
Performance of PID is under analyzing

38. Summary
T2K experiment, which aims to measure the final unknown oscillation amplitude (i.e. mixing angle) q13, starts from 2009-April.
We are accumulating the candidate events at Super-Kamiokande. We will have good physics results soon.
In next generation experiment, we’d like to quest the CP violation of lepton sector. (with huge liquid Argon TPC and intense beam)

39. Supplements

40. Three Flavor Mixing in Lepton Sector
mass eigenstates
Weak eigenstates m1 ne m2 nm nt m3
cij = cosqij, sij=sinqij
q12, q23, q13
+ d (+2 Majorana phase)
Dm122, Dm232, Dm132