1. Results from K2K and status of T2K
Yuichi Oyama (KEK)
Sep

2. Overview of the K2K experiment
First long-baseline neutrino oscillation experiment. ( ) ●
Confirmation of nm-nt oscillation reported by Super-Kamiokande using artificial neutrino beam. ●
Muon neutrino beam generated at KEK is shot toward the Super-Kamiokande detector, which is 250km away from KEK ●
Search for neutrino oscillations in the parameter region Dm2 > 2×10-3 eV2 is possible. It covers the parameter regions suggested by the atmospheric neutrino anomaly. ●

3. K2K neutrino beamline in KEK
TRISTAN RING
(B-factory)
12GeV PS
Primary Beam-line P
12GeV/c proton beam
1.1msec beam duration
Al Target
2.2sec accelerator cycle
Intensity 5~6x1012 ppp
Decay pipe
(200m)
Total 1020 p.o.t.
p+ -> m+ + nm
Muon Pit
Front Detectors nm
To Kamioka

4. Property of the neutrino beam
The mean energy is about 1.3GeV and the peak energy is about 1.0GeV. ●
Almost pure muon neutrino beam. ne/nm ratio is about 1%. ●
The direction of the beam is adjusted within 1mrad. ●
Nearly the same energy spectrum and flux within 3 mrad. ●
It covers the size of SK; ~50m/250km = 0.2mrad.
Neutrino flux at SK (250km downstream) is 1.3x106n/cm2 for 1020p.o.t. and ~170 events are expected in the 22.5kton of fiducial volume in the case of null oscillation. ●
profile at SK 1 3 2
3mrad
n/cm2 (x106)
distance (km)
SK(0.2mrad)
spectrum at SK 1 2 3 4 5
Neutrino energy (GeV)
n/cm2 /0.1GeV(x106)

5. K2K Front Detectors at 300m from the target
(a)1kt water Cherenkov detector (1kt)
An 1/50 miniature of SK detector. Direct comparison with SK data
(b)Fine-Grained Detector (FGD)
Consists of 4 detector elements.
Precise measurement of neutrino beam property.

6. Study of the Neutrino beam in the Front Detectors
Data recorded in the Front Detectors are used to study properties of the neutrino beam. ●
Fine-Grained detector
1kt detector
The beam direction, stability of the beam intensity, energy spectrum, ne/nm ratio well agree with expectations. ●
The excellent agreements between data and expectations in KEK site ensure the reliability of the expected beam at SK site. ●

7. Summary of data-taking in K2K
First neutrino beam: January 27, 1999 ●
Physics run: Jun 4, 1999 – Jul 12, 2001 (K2K-I) ●
Super-Kamiokande accident
Jan 17, 2003 – Nov 6, 2004 (K2K-II) ●
Total physics run: days　( ) ●
Total spill numbers: x106 spill ●
Total POT for analysis: x1018 p.o.t. (47.9x x1018)
Year
protons/pulse
(x1012) 5
Total POT
(x1018)
100
Delivered Protons on Target (POT)

8. time correlation with the neutrino beam
Neutrino events in Super-Kamiokande
Selection
Evis > 30 MeV and no signal in the outer detector ●
Events within 1.5msec time window are selected because neutrino beam width is 1.1msec and accuracy of the absolute time determination by GPS is 0.2msec.
History of event accumulation ●
# of events
time correlation with the neutrino beam
Number of events
GPS
Kamioka
KEK
1.5ms
Results
P.O.T. (x1018)
Number of events in the fiducial volume is 112. ●
Expected atmospheric neutrino background is 2.5x10-3 events.
The rate of the neutrino events is uniform. ●

9. A typical K2K neutrino event in Super-Kamiokande
The event seems to be quasi-elastic scattering interaction; ●
nm + n m- + p
Neutrino energy can be calculated from muon energy and opening angle from KEK direction. ●
mNEm - mm2/2
En =
mN - Em + Pmcosqm-KEK

10. nm-nt oscillation analysis for K2K data1 2 3 4 5 En
P(nm nm)
Neutrino Survival probability
(1)We observed 112 neutrino
events where the expectation is 155.9　　　 .　Number of neutrino events is considerably smaller than expectation.
Dm2=3.0x10-3eV2, sin22q=1.0, L=250km
+13.6
-15.6
(2)Neutrino energy distribution is
data
calculated from 58 single ring m-like events.
No oscillation
Best fit
The result shows a clear discrepancy in GeV range. It reflects energy dependence of neutrino survival probability
Number of neutrino events
No oscillation
(normalized to data)
If null oscillation is assumed, such poor agreements happen with a probability of 0.003%.
Neutrino energy (GeV)

11. Constraints on nm-nt oscillation
Dm2 ranges (1.88~3.48)x10-3eV2 for ●
The best fit parameters are (Dm2,sin22q)=(2.76x10-3eV2, 1.0). ●
The expectation of the total SK events is 107.7, where data is 112.
Agreement with the SK atmospheric neutrino results is excellent. ●
Dm2 (eV2)
10-1
10-2
10-3
10-4
0.2
0.4
0.6
0.8 1
sin22q
Shape of oscillation contours by two experiments are different.
SK atmospheric neutrino data is high statistics (~10000 events), but poor L and En determination. Sensitive to sin22q.
K2K data is low statistics (~100 events), but L is constant and good En determination. 　　　Sensitive to Dm2.
SK atmospheric neutrino
(90%C.L.)
They play complementary roles in determination of the oscillation parameters.

12. T2K experiment 295km J-PARC in JAERI
KEK
Kamioka
Tokai
J-PARC in JAERI
Next generation long-baseline neutrino-oscillation experiment; ●
from Tokai to Kamioka
High intensity neutrino beam from JHF 50GeV Proton Synchrotron in J-PARC is shot toward the Super-Kamiokande detector 295km away. ●
Nominal beam intensity is about 100 times larger than K2K. ●
Letter of Intent : hep-ex/

13. What is J-PARC, JAERI, Tokai, T2K…..
J-PARC : Japan Proton Accelerator Research Complex.
J-PARC in JAERI, Tokai
To SK
400MeV Linac
3GeV PS
50GeV PS
Pacific Ocean
Decay Volume
Target
The name of the entire project. It includes
High Energy Physics, Nuclear Physics, Life Science, Material Science, Nuclear Technology. Accelerators consist of 400MeV Linac, GeV PS and 50GeV PS.
JAERI : Japan Atomic Energy Research Institute.
The host institute of J-PARC
Tokai : the name of the village where JAERI is located.
JHF : Japan Hadron Facility. 50GeV Proton Synchrotron
T2K = JHFn = J-PARC n : Name of the neutrino experiment.
J-PARC is under construction since 2001. ●
T2K experiment was officially approved in December The construction started in April 2004, and the experiment will start in 2009. ●

14. T2K Beamline and Detectorsp n
140m 0m
280m
2 km
295 km
on-axis
off-axis
Comparison of the proton beam
Beamline
The center of the beam direction is adjusted to be 2o ~ 3o off from the SK direction.
K2K
T2K
Eproton (GeV) 12 50
Beam Power (kW)
5.2
750
Protons per second
3x1012
1x1014 ●
Off Axis beam
Detectors
Muon ~140m downstream ●
First near ~280m downstream (boundary of the JAERI site) ●
Second near ~2km downstream ●
Far 295km downstream (Super-Kamiokande) ●
“x100 high intensity” and “Off axis beam” and “2km detector”

15. Requirements for Neutrino Energy
Neutrinos of En=0.5~1.0GeV are desired from 3 reasons. 1 2 3 4 5 En
P(nm nm)
(1)
The oscillation probability is maximum for En = 0.5~1.0 GeV
Neutrino Survival probability
Dm2=2.5x10-3eV2, sin22q=1.0, L=295km
(2)
Neutrino energy is calculated from quasi-elastic scattering events;
nm + n
m + p
Neutrino cross section
quasi-elastic scattering
by simple 2-body kinematics.
Other neutrino interactions are background to select quasi-elastic scattering.
Fraction of quasi-elastic scattering is smaller for high energy neutrinos.
(3)
Water Cherenkov detector has better performance for single ring events.

16. Off-axis beam How to adjust neutrino energy to 0.5~1.0GeV q OA2.5°●
The center of the beam direction is adjusted to be 2o ~ 3o off from the SK direction. Although neutrino intensity at SK is lower, the peak energy is low and high energy neutrinos are suppressed.
Neutrino energy spectrum is quasi-monochromatic.
OA3°
OA0°
OA2°
OA2.5°
Off Axis Beam
Arbitrary Unit
En (GeV) q
beamline SK
Oscillation study is most effective if neutrino peak energy is adjusted to the oscillation maximum; Epeak = Eoscmax. ●
Off Axis Angle
2.0o
2.1o
2.4o
3.0o
Epeak(GeV)
0.782
0.756
0.656
0.520
Dm232(x10-3eV2)
3.28
3.17
2.75
2.18
Dm232 is calculated from Dm232=pEoscmax/2.54L
Present Dm232 from other experiments is Dm232 ~ (2~3)x10-3eV2
The problem is the oscillation maximum has still large uncertainty. ●

17. Tunability of the beam direction and shape of the decay pipe
Keep a tunability of the beam direction and wait other experiments. ●
Hyper-Kamiokande (1Mt WC) will be proposed at 10km away from SK The beam direction can be adjusted to 2o ~ 3o off both from SK and HK. ●
To satisfy this condition, the cross section of the decay pipe is rectangular, and the height of the pipe is larger in downstream. ●
Map in Kamioka
Side view of decay pipe SK
2.0o
Beam eye
3.0o
2.5o SK HK
~10km
We will fix the beam direction after knowing the MINOS results in 2008 summer conferences. ● ● HK
Cross section of decay pipe

18. 2km detector 2km detector q
A water Cherenkov detector is definitely needed as a front detector. ●
However…., we have two difficulties.
(1)
Neutrino beam intensity is too high The event rate is 60 events/spill/1kt at the 280m detector site.
(2)
110m of neutrino production point must be viewed as “point like” for reliable flux extrapolation to SK. q SK ●
Construct a water Cherenkov detector at an appropriate distance.
2km detector
Muon range counter
(Not approved yet)
Water Cherenkov
Fine grained detector
2km
target

19. = U Neutrino mass matrix and physics goal of T2K
If neutrinos have mass, the flavor eigenstates are mixtures of the mass eigenstates. The neutrino mass matrix, U, has 6 parameters. ● ne n1
2 square mass differences (Dm122, Dm232), nm n2
= U
3 mixing angles (q12,q23,q13) nt n3
1 CP violation phase, d.
Dm122 and q12 were determined by solar/reactor neutrino oscillation. ●
Dm122 ~ (6~8)x10-5eV2, sin22q12 ~ 0.8
Dm232 and q23 were determined by atmospheric/K2K neutrino oscillation. ●
Dm232 ~ (2~3)x10-3eV2, sin22q ~
>
Remaining unknown parameters are q13 and d. ●
Complete understanding of neutrino mass matrix
(1)First observation of finite q13 from ne-nm oscillation
(2)Precise measurements of Dm232 and q23 from nm-nt oscillation
(3)Observation of d after a beam intensity upgrade (0.75MW ->4MW)
and construction of Hyper-Kamiokande.

20. Measurement of q13 by ne appearance
q13 can be determined by observing ne appearance. ●
P(nm ne) ~ sin2q23sin22q13sin2(1.27Dm232L/En)
sin2q23~0.5
Dm232 ~ (2~3)x10-3eV2
(the same Dm2 as atm. n oscillation)
q13 is expected to be small because it is the mixing angle between 1st and 3rd generation. Present upper limit is sin22q13 ~ 0.1 (CHOOZ).
Small ne appearance signal must be searched for.
Preliminary results from K2K
Only 1 Single ring e-like events remains after e/m particle ID algorithm
and p g rejection. ●
We expect 1.63 background (nmNC and beam ne) and
1~2 oscillation signal for parameters around the CHOOZ limit. ●
The limit is sin22qem (~sin22q13/2) < 0.18 for Dm2=2.5x10-3eV2.
No impact on present limit. Obviously, statistics is too small.
Prospects in T2K
Beam intensity is 100 times higher and ~100 ne signals are expected. “Neutrino energy cut” can be applied because neutrino energy is quasi-monochromatic. ●
Sensitive to sin22q13 > region.

21. Prospect for nm-nt oscillation
Dm232 and q23 were already measured by Super-Kamiokande/K2K. ●
Dm232 ~ (2~3)x10-3eV2, sin22q ~
>
More precise determination of oscillation parameters is attained from precise measurement of neutrino survival probability as a function of neutrino energy. ●
Neutrino Survival probability 1
P(nm nm)
sin22q23
Dm2=2.5x10-3eV2, sin22q=1.0, L=295km 1 2 3 4 5
Eoscmax En
Dm232 can be determined from position of the oscillation maximum Eoscmax; ●
pEoscmax
Dm232 =
2.54L
From ~ 5% accuracy of Eoscmax measurement,
D(Dm232 )~0.1x10-3eV2 is possible.
sin22q23 can be determined from depth of the dip, or reduction of the neutrino events. Because of ~10000 event statistics (5years), D(sin22q23)~0.025 is attainable. ●

22. Summary
K2K
( )
From 92.2x1018 p.o.t., 112 neutrino events are observed in SK, where expectation based on Front detector data is 155.9 ●
+13.6
-15.6
A distortion of the neutrino energy spectrum is also obvious.
Probability of null oscillation is 0.003% ●
Dm2 ranges (1.88~3.48)x10-3eV2 for This result is consistent with Super-Kamiokande
Only 1 possible ne signal was found. ●
It is consistent with nmNC + beam ne background; 1.63.
No impact on the present limit from other experiments.
T2K
( )
Keywords: ●
~100 x K2K
Tunable off-axis beam
2km detector
Complete understanding of neutrino mass matrix ●
(1)First observation of finite q13 if sin22q ~
>
(2)Precise measurements of Dm232 and q23
D(Dm232 )~0.1x10-3eV2, D(sin22q23)~0.025

23. Milestones of Super-Kamiokande, K2K and T2K
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
SK-I
SK-II
Since Apr. 1996
SK-III
Half recover
SK accident
Full recover
K2K-I
K2K-II
T2K construction
T2K
MINOS
CNGS
Today

24. Thank you!

25. Super-Kamiokande
50kt water Cherenkov detector with inch F PMTs. ●
Located at 1000m underground in Kamioka mine, Japan ●
Operation since April 1996. ●
Discovery of neutrino mass using atmospheric neutrinos. ● ●
Precise study of solar neutrino oscillations.

26. Super-Kamiokande accident on November 12, 2001
The implosion of one PMT created shock waves which triggered a chain reaction to destroy the other PMTs. ● ●
6661 inner PMTs and 1017 outer PMTs were broken.
Remaining ~5200 PMTs are covered by Acrylic + FRP　vessels. The experiment was restarted with about half PMT density in December 2002. ●

27. K2K-I Front Detectors at 300m from the target
Trigger counters
(a)1kt water Cherenkov detector (1kt)
An 1/50 miniature of SK detector. Direct comparison with SK data
(b)Fine-Grained Detector (FGD)
Consists of 4 detector elements.
Precise measurement of neutrino beam property.

28. Study of the Neutrino beam in the Front Detectors
Data recorded in the Front Detectors are used to study properties of the neutrino beam. ●
Fine-Grained detector(K2K-I)
1kt detector
100cm
The beam direction, stability of the beam intensity, energy spectrum, ne/nm ratio well agree with expectations. ●
The excellent agreements between data and expectations in KEK site ensure the reliability of the expected beam at SK site. ●

29. Detector upgrade in K2K-II
For more precise study of neutrino interactions in sub-GeV range, a new detector SciBar has been installed. ●
Full active solid scintillator tracker. ●
14400 channels of 1.3cm x 2.5cm x 3m scintillator bar which contain wavelength shifting fibers inside.
Even short track of less than 4cm can be recognized. ●

30. Summary of K2K neutrino events in Super-Kamiokande
Observed Expected
(no oscillation)
All (FCFV)
112
155.9
total event analysis
Single Ring 67
99.0
m-like 58
90.8
energy spectrum
e-like 9
8.2
(tight e-like)
(1)
(1.63)
ne appearance
Multi Ring 45
56.8
This is for the entire period including both K2K-I and K2K-II.
Again, muon directions was stable within 1mrad.
FCFV = Fully Contained, Fiducial Volume ● ●
“tight e-like cut” requires absence of delayed electron signal from m->e decay, and also rejects possible p0-> 2g events by finding second e-like ring forcibly.

31. MINOS experiment ( )
Long-baseline neutrino-oscillation experiment from Fermilab 120GeV main injector (0.4MW) to Soudan mine 735km away. ● ●
The detectors are “sandwich” of 2.54cm thick steel plane and 1cm thick scintillator in 1.5Tesla toroidal magnets. Total mass are 5.4kt for far detector and 0.98kt for near detector
Fermilab
Soudan
735km ●
In low energy (LE) beam configuration, the peak energy is about 3GeV and ~2500 nm charged current events are expected in the far detector in 1 year.
If q13 is close to CHOOZ limit, ne appearance signal can be found with 3s significance with 3 years of operation. ● ●
With 5 years operation, Dm232 can be measured with 10% accuracy.

32. CNGS project ( )
CERN Neutrino to Gran Sasso. Wide band nm beam from CERN 400GeV SPS is shot toward Gran Sasso laboratory 732km away. ● ●
The neutrino beam is optimized for nt appearance; <En>=17GeV.
Two experiments are under preparation. ●
(June )
OPERA
Emulsion+Pb sandwich and spectrometer. Total mass is 1700 tons.
If Dm232 = 2.4x10-3eV2, 12.8 nt events are expected in 5 years of operation where background is 0.8.
ICARUS
(Summer )
Liquid Ar detector of 5 x 600ton modules.
If Dm232 = 2.5x10-3eV2, 11.9 nt events are expected in 5 years of 5 module (3000ton) operation, where background is 0.7.
First 600ton module will be ready by summer 2006, and other two 600ton modules will be completed by end of 2007.