Results from K2K and status of T2K

Crimea2005@Yalta

Yuichi Oyama (KEK)

Sep-11-2005

Overview of the K2K experiment●

●

●

First long-baseline neutrino oscillation experiment. (1999-2004)

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 m2 > 2×10-3 eV2 is possible. It covers the parameter regions suggested by the atmospheric neutrino anomaly.

● Confirmation of - oscillation reported by Super-Kamiokande using artificial neutrino beam.

PPrimary Primary Beam-lineBeam-line

12GeV/c proton beam12GeV/c proton beamAl TargetAl Target

Front DetectorsFront Detectors

Dec

ay p

ipe

Dec

ay p

ipe

(200

m)

(200

m)

TRISTAN RING TRISTAN RING (B-factory)

(B-factory)

Muon PitMuon Pit

K2K neutrino beamline in KEK

1.11.1sec beam durationsec beam duration2.2sec accelerator cycle2.2sec accelerator cycle

12GeV PS12GeV PS

Intensity 5~6x10Intensity 5~6x101212 ppp ppp

To KamiokaTo Kamioka

-> -> + +

Total 10Total 102020 p.o.t. p.o.t.

profile at SK

00

1

31 2

3mrad

/cm

2 (x

106 )

distance (km)

SK(0.2mrad)

spectrum at SK

0 1 2 3 4 5Neutrino energy (GeV)

/cm

2 /0

.1G

eV(x

106 )

0

5

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. e/ ratio is about 1%.

● 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 1.3x106/cm2 for 1020p.o.t.

and ~170 events are expected in the 22.5kton of fiducial volume in the case of null oscillation.

● The direction of the beam is adjusted within 1mrad.

　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.

Study of the Neutrino beam in the Front Detectors

1kt detectorFine-Grained detector

● The excellent agreements between data and expectations in KEK site ensure the reliability of the expected beam at SK site.

● Data recorded in the Front Detectors are used to study properties of the neutrino beam.

● The beam direction, stability of the beam intensity, energy spectrum, e/ ratio well agree with expectations.

1999 2000 2001 2002 2003 2004Year

prot

ons/

puls

e(x

1012

)

0

5

Tot

al P

OT

(x10

18)

0

100Delivered Protons on Target (POT)

Summary of data-taking in K2K● First neutrino beam: January 27, 1999● Physics run: Jun 4, 1999 – Jul 12, 2001 (K2K-I)

● Total physics run: 442.8 days 　 (233.7+209.1)

● Total POT for analysis: 92.2x1018 p.o.t. (47.9x1018 + 44.3x1018)

● Total spill numbers: 17.4x106 spill

Jan 17, 2003 – Nov 6, 2004 (K2K-II)

Super-Kamiokande accident

1.5sGPS

KamiokaKEK

Neutrino events in Super-Kamiokande

● Evis > 30 MeV and no signal in the outer detector

Number of events in the fiducial volume is 112.●

Expected atmospheric neutrino background is 2.5x10-3 events.

Events within 1.5sec time window are selected because neutrino beam width is 1.1sec and accuracy of the absolute time determination by GPS is 0.2sec.

●

The rate of the neutrino events is uniform.●

Selection

ResultsN

um

be

r o

f ev

en

ts

History of event accumulation

P.O.T. (x1018)

# of eventstime correlation with the neutrino beam

　A typical K2K neutrino event in Super-Kamiokande

n

p

The event seems to be quasi-elastic scattering interaction;

●

Neutrino energy can be calculated from muon energy and opening angle from KEK direction.

●

mNE - m2/2

E = mN - E + Pcos-KEK

events where the expectation is 155.9 　　　 . 　 Number of neutrino events is considerably smaller than expectation.

0 1 2 3 4 50

1

E

P

)

+13.6-15.6

(1)We observed 112 neutrino

(2)Neutrino energy distribution is

-oscillation analysis for K2K data

calculated from 58 single ring -like events.The result shows a clear discrepancy in 0.5-1.0GeV range. It reflects energy dependence of neutrino survival probability

If null oscillation is assumed, such poor agreements happen with a probability of 0.003%.

Neutrino energy (GeV)

Nu

mb

er

of

ne

utr

ino

ev

ents

data

No oscillation

Best fit

No oscillation(normalized to data)

m2=3.0x10-3eV2, sin22=1.0, L=250km

Neutrino Survival probability

Constraints on-oscillation

The best fit parameters are (m2,sin22)=(2.76x10-3eV2, 1.0).●

The expectation of the total SK events is 107.7, where data is 112.

m2 ranges (1.88~3.48)x10-3eV2 for sin22=1.0@90%C.L.●

●

m2

(eV

2)

10-1

10-2

10-3

10-4

0 0.2 0.4 0.6 0.8 1sin22

Agreement with the SK atmospheric neutrino results is excellent.

SK atmospheric neutrino(90%C.L.)

Shape of oscillation contours by two experiments are different.

SK atmospheric neutrino data is high statistics (~10000 events), but poor L and E determination. Sensitive to sin22.

K2K data is low statistics (~100 events), but L is constant and good E determination. 　　　Sensitive to m2.

They play complementary roles in determination of the oscillation parameters.

T2K experiment

295km

KEK

KamiokaTokai

● Next generation long-baseline neutrino-oscillation experiment;

● 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.

J-PARC in JAERI

Letter of Intent : hep-ex/0106019

from Tokai to Kamioka

The name of the entire project. It includes

JAERI : Japan Atomic Energy Research Institute.

Tokai : the name of the village where JAERI is located.

What is J-PARC, JAERI, Tokai, T2K…..

J-PARC : Japan Proton Accelerator Research Complex.

The host institute of J-PARC

J-PARC in JAERI, Tokai

To SK

400MeV Linac

3GeV PS

50GeV PS

Pacific Ocean

Decay Volume

Target

High Energy Physics, Nuclear Physics, Life Science, Material Science, Nuclear Technology. Accelerators consist of 400MeV Linac, 3GeV PS and 50GeV PS.

● J-PARC is under construction since 2001.

● T2K experiment was officially approved in December 2003. The construction started in April 2004, and the experiment will start in 2009.

JHF : Japan Hadron Facility. 50GeV Proton Synchrotron

T2K = JHF = J-PARC : Name of the neutrino experiment.

K2K T2K

Eproton (GeV) 12 50

Beam Power (kW) 5.2 750

Protons per second 3x1012 1x1014

p

140m0m 280m 2 km 295 km

on-axis

off-axis

T2K Beamline and Detectors

● Muon monitors @ ~140m downstream

First near detectors@ ~280m downstream (boundary of the JAERI site)

Second near detectors@ ~2km downstream

Far detector@ 295km downstream (Super-Kamiokande)

●

●

●

Detectors

Beamline

Off Axis beam

● The center of the beam direction is adjusted to be 2o ~ 3o off from the SK direction.

“x100 high intensity” and “Off axis beam” and “2km detector”

Comparison of the proton beam

Neutrino cross section

quasi-elastic scattering

Requirements for Neutrino Energy

+ n + p

Neutrino energy is calculated from quasi-elastic scattering events;

The oscillation probability is maximum for E = 0.5~1.0 GeV

0 1 2 3 4 50

1

E

P

)

m2=2.5x10-3eV2, sin22=1.0, L=295km

Neutrino Survival probability

Other neutrino interactions are background to select quasi-elastic scattering.

by simple 2-body kinematics.

Neutrinos of E=0.5~1.0GeV are desired from 3 reasons.

Fraction of quasi-elastic scattering is smaller for high energy neutrinos.

(1)

(2)

Water Cherenkov detector has better performance for single ring events.

(3)

OA3°

OA0°OA2°

OA2.5°

Off Axis Beam

Arb

itra

ry U

nit

E (GeV)

Off Axis Angle 2.0o 2.1o 2.4o 3.0o

Epeak(GeV) 0.782 0.756 0.656 0.520

m232(x10-3eV2) 3.28 3.17 2.75 2.18

beamline

SK

●

●

How to adjust neutrino energy to 0.5~1.0GeV

Oscillation study is most effective if neutrino peak energy is adjusted to the oscillation maximum; Epeak = Eoscmax.

The problem is the oscillation maximum has still large uncertainty.

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.

Off-axis beam

Present m232 from other experiments ism23

2 ~ (2~3)x10-3eV2

Neutrino energy spectrum is quasi-monochromatic.

●

m232

is calculated from m232=Eoscmax/2.54L

2.0o

Beam eye3.0o2.5o2.0o

SKHK

SK

~10km

HK

Tunability of the beam direction and shape of the decay pipe

●

To satisfy this condition, the cross section of the decay pipe is rectangular, and the height of the pipe is larger in downstream.

●

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.

Map in KamiokaSide view of decay pipe

Keep a tunability of the beam direction and wait other experiments.●

Cross section of decay pipe

We will fix the beam direction after knowing the MINOS results in 2008 summer conferences.

● ●

2kmtarget

●

SK●

2km detector

2km detectorA water Cherenkov detector is definitely needed as a front detector.

Neutrino beam intensity is too high. The event rate is 60 events/spill/1kt at the 280m detector site. 110m of neutrino production point must be viewed as “point like” for reliable flux extrapolation to SK.

Construct a water Cherenkov detector at an appropriate distance.

Muon range counter

Water Cherenkov

Fine grained detector

(1)

(2)

However…., we have two difficulties.

(Not approved yet)

m232

and 23 were determined by atmospheric/K2K neutrino oscillation.●

Remaining unknown parameters are 13 and .●

(3)Observation of after a beam intensity upgrade (0.75MW ->4MW)

If neutrinos have mass, the flavor eigenstates are mixtures of the mass eigenstates. The neutrino mass matrix, U, has 6 parameters.

1

2

3

e

= U

●

1 CP violation phase,

2 square mass differences (m122, m23

2), 3 mixing angles (12,23,13)

m122

and 12 were determined by solar/reactor neutrino oscillation.●

m122

~ (6~8)x10-5eV2, sin2212 ~ 0.8

m232

~ (2~3)x10-3eV2, sin2223 0.9

Neutrino mass matrix and physics goal of T2K

~>

(1)First observation of finite 13 from e- oscillation

(2)Precise measurements of m232 and 23 from -oscillation

Complete understanding of neutrino mass matrix

and construction of Hyper-Kamiokande.

Measurement of 13 by e appearance●

P(e) ~ sin223sin2213sin2(1.27m232L/E)

m232 ~ (2~3)x10-3eV2

13 can be determined by observing e appearance.

sin223~0.5

13 is expected to be small because it is the mixing angle between 1st and 3rd generation. Present upper limit is sin2213 ~ 0.1 (CHOOZ).

the samem2 as atm. oscillation)

Small e appearance signal must be searched for.

Beam intensity is 100 times higher and ~100 e signals are expected. “Neutrino energy cut” can be applied because neutrino energy is quasi-monochromatic.

●

Only 1 Single ring e-like events remains after e/ particle ID algorithm and 0 2 rejection.

Preliminary results from K2K

We expect 1.63 background (NC and beam e) and 1~2 oscillation signal for parameters around the CHOOZ limit. The limit is sin22e (~sin2213/2) < 0.18 for m2=2.5x10-3eV2.No impact on present limit. Obviously, statistics is too small.

Prospects in T2K

Sensitive to sin2213 > 0.006 region.

●

●

m232

and 23 were already measured by Super-Kamiokande/K2K.●

More precise determination of oscillation parameters is attained from precise measurement of neutrino survival probability as a function of neutrino energy.

●

m232

~ (2~3)x10-3eV2, sin2223 0.9

Prospect for - oscillation

~>

0 1 2 3 4 50

1

EP

) m2=2.5x10-3eV2, sin22=1.0, L=295km

Neutrino Survival probability

m232

can be determined from position of the oscillation maximum Eoscmax;

●

m232

=2.54L

Eoscmax

Eoscmax

From ~ 5% accuracy of Eoscmax measurement, (m23

2 )~0.1x10-3eV2 is possible.● sin2223 can be determined from depth of the dip, or reduction of

the neutrino events. Because of ~10000 event statistics (5years), (sin2223)~0.025 is attainable.

sin

22 2

3

SummaryK2K

● From 92.2x1018 p.o.t., 112 neutrino events are observed in SK, where expectation based on Front detector data is 155.9

Probability of null oscillation is 0.003%m2 ranges (1.88~3.48)x10-3eV2 for sin22=1.0@90%C.L. This result is consistent with Super-Kamiokande

T2K

● Complete understanding of neutrino mass matrix

● Keywords:

~100 x K2K 2km detectorTunable off-axis beam

A distortion of the neutrino energy spectrum is also obvious.

(1999 - 2004)

Only 1 possibleesignal was found. ●

●

+13.6-15.6

It is consistent with NC + beam e background; 1.63.

No impact on the present limit from other experiments.

(2009 - )

(1)First observation of finite 13 if sin2213 0.006.

(2)Precise measurements of m232 and 23

~>

(m232

)~0.1x10-3eV2, (sin2223)~0.025

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Milestones of Super-Kamiokande, K2K and T2K

Today

SK accident

SK-IISK-I

T2K construction

Since Apr. 1996

K2K-IK2K-II

Half recoverFull recover

SK-III

T2K

MINOS

CNGS

Thank you!

Super-Kamiokande● 50kt water Cherenkov detector with 11146 20-inch 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.

●

Super-Kamiokande accident on November 12, 2001

● 6661 inner PMTs and 1017 outer PMTs were broken.

● The implosion of one PMT created shock waves which triggered a chain reaction to destroy the other PMTs.

● Remaining ~5200 PMTs are covered by Acrylic + FRP 　 vessels. The experiment was restarted with about half PMT density in December 2002.

　K2K-I 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.

Trigger counters

Study of the Neutrino beam in the Front Detectors

100cm

1kt detectorFine-Grained detector(K2K-I)

● The excellent agreements between data and expectations in KEK site ensure the reliability of the expected beam at SK site.

● Data recorded in the Front Detectors are used to study properties of the neutrino beam.

● The beam direction, stability of the beam intensity, energy spectrum, e/ ratio well agree with expectations.

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.

Summary of K2K neutrino eventsin Super-Kamiokande

FCFV = Fully Contained, Fiducial Volume

Observed Expected(no oscillation)

All (FCFV)Single Ring

Multi Ring

-like

e-like

112 155.9

9

45

58

67 99.0

56.8

90.8

8.2(tight e-like) (1) (1.63)

total event analysis

energy spectrum

e appearance

●

● “tight e-like cut” requires absence of delayed electron signal from ->e decay, and also rejects possible 0-> 2events by finding second e-like ring forcibly.

MINOS experiment (2004 - )● Long-baseline neutrino-oscillation experiment from Fermilab 120GeV

main injector (0.4MW) to Soudan mine 735km away.

● If 13 is close to CHOOZ limit, ne appearance signal can be found with 3 significance with 3 years of operation.

● With 5 years operation, m232 can be measured with 10% accuracy.

● 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

● In low energy (LE) beam configuration, the peak energy is about 3GeV and ~2500 charged current events are expected in the far detector in 1 year.

Fermilab

Soudan

735km

CNGS project (2006 - )● 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 appearance; <E>=17GeV.

● Two experiments are under preparation.

OPERAEmulsion+Pb sandwich and spectrometer. Total mass is 1700 tons.If m23

2 = 2.4x10-3eV2, 12.8 events are expected in 5 years of operation where background is 0.8.ICARUS

Liquid Ar detector of 5 x 600ton modules.

First 600ton module will be ready by summer 2006, and other two 600ton modules will be completed by end of 2007.

If m232 = 2.5x10-3eV2, 11.9 events are expected in 5 years of

5 module (3000ton) operation, where background is 0.7.

(June 2006 - )

(Summer 2006 - )