Indication of electron
neutrino appearance
in the T2K experiment
Yoshihisa OBAYASHI for the T2K collaboration
July 20th, 2011
Kamioka Observatory, Institute for Cosmic Ray Research, Univ. of Tokyo

2011年7月20日水曜日

1

2011年7月20日水曜日

2

Neutrino Oscillation
Flavor Eigenstate (νe,νμ,ντ) ≠ Mass Eigenstate (ν1,ν2,ν3)%"# ( % cos+ sin + (% " i (α,β = Flavor states' * ='' **i,j = Mass states"& $ ) & ,sin + cos+ )&" j )Probability that να observed as νβ after traveling L:
2

2

1.27"m (eV )L(km)P(! " ! ! # ) = sin (2$ )sin ()!
E! (GeV )222Δm2 =|mi2-mj2|

2

1.27"m (eV )L(km)! ! # ) = sin (2$ )sin ()! E! (GeV )
!
2

2

#

!"
0
2011年7月20日水曜日

!#

#

!"

!"

!
3

Three Flavour Oscillation

UPMNS=

Oscillation between three neutrino flavors are represented
by three mixing angle (θ12,θ23,θ13), two mass differences2
2(Δm 12, Δm 23) and CP phase δ.
2011年7月20日水曜日

4Current Status of Experimental Knowledge
θ12 = 34° ± 3°
Δm122~8×10-5eV2
solar ν, reactor ν|Ue3|2

θ23 = 45° ± 5°Δm232~2.5×10-3eV2
atmospheric ν, accelerator νθ13 < 11°
reactor ν, accelerator ν
Last Unknown mixing angle θ13
sin2(2θ13)<0.15 @90%CL
by CHOOZ, MINOS
2011年7月20日水曜日

normalinverted

Mass Hierarchy (m3 >? <? m1,m2),
CP phase δ:
UNKNOWN.
5

Physics Motivation of νe appearance★ discovery of νμ → νe
Direct detection of neutrino flavor
mixing in “appearance” mode then Determine

θ13

P(νμ→νe) =2
2
22
sin 2θ13 sin θ23 sin (1.27Δm 31 L/E) + ...
(Δm223 ~ Δm231)
Cf: In Reactor experiment,P(νe→νx) =sin22θ13 sin2(1.27Δm231 L/E) + ...

Open a possibility to measure
CP violation in lepton sector in future
CP odd term in P(νμ→νe)sinθ12sinθ13sinθ23sinδ
2011年7月20日水曜日

6

T2K(Tokai-to-Kamioka)
experiment
T2K (Tokai to Kamioka) experiment

!"#実験

市川温
%&'$()*$!



High intensity QP beam from J-PARC MR to Super-Kamiokande @
295km
T2K
Main Goals:

Discovery
Determine T13→ νe oscillation Æ(νe appearance)★ DiscoveryofofQνeμ appearance
Last unknown mixing angle
Precision
measurementofinνlepton
μ disappearance★
Openpossibility
to explore CPV
sector

2011年7月20日水曜日

7

T2K Collaboration

!"#実

市川
%&'$()*

International collaboration(~500 members, 59 institutes, 12 countries）
2011年7月20日水曜日

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2011年7月20日水曜日

9

Overview of this talk
1. Introduction of T2K experiment
2. Search for νe appearance with 1.43 x 1020 protons on target (p.o.t)- Analysis overview- νe selection- The expected number of events at Far detector- Systematic uncertainty- Results
3. Conclusion

2011年7月20日水曜日

10

Experimental Setupptarget/Horn

Decay volume!

Muon
detector

Near
Detector
off-axis (2.5°)

proton0m

2011年7月20日水曜日

on-axisπ→μν

30GeV protons
from J-PARC MR!"

Far Detector(Super-K)

118
110 m

280 m

295 km11

J-PARC Neutrino beam facility
Horn1 Installation!

!"#$%&&%'(")#*++,,-,-)(").%"/)01#$/)

Muon Monitor

Horn

Beam monitors

Si array+ IC array

Super-Conducting
Magnets
intensity, position
profile3 Horns w/ 250kA

to Super-K

νμNear detector

μ+

+

!

3(%#345#/)26%/&+>*&5?*<.:/><
DecayVolume Target(at 280m from target)!"#$%&'()*+,"#-.//0&+#1"#!)2%//)

30GeV
MR

Beam Dump
2011年7月20日水曜日

110m length

Graphite,-.2'/#7089%2#:%/;
Φ26 x
Helium cooling
900 mm longproton beam
12

Run 2

Run 1
145kW

50kW

Run 1 (Jan. ʼ10 - June ʼ10)
- 3.23 x 1019 p.o.t. for analysis- 50kW stable beam operation# of bunch : 6 → 8
rep. rate : 3.64s→ 3.2s → 3.04s

proton per pulse

accumulated # of protons

Total # of protons used for analysis

Run 2 (Nov. ʼ10 - Mar. ʼ11)
- 11.08 x 1019 p.o.t. for analysis- ~145kW beam operation

Total # of protons used for this analysis is 1.43 x 1020 pot
2% of T2Kʼs final goal and x 5 exposure of the previous report
2011年7月20日水曜日

13

Far Detector(Super-K)
target/Hornpproton!"!

Eν (GeV)

Off-axis beam : intense & narrow-band
beam
BNL E889 Design Report(1995)
0°
1

2°
3°

#
on-axisDecay volume
Oscillation Prob.＠!m2=3x10-3eV2

OA2°
OA2.5°OA3°
OA2.5°
OA2°
OA3°

OA0°

0

0

2

2.5°

5

8

Pπ(GeV)

Beam energy at oscillation max.
(based on Δm223 & L=295km)
Eν ~ 0.6 GeV→ T2K off-axis angle is 2.5°
(maximize physics sensitivity)

Small νe component (0.5%@peak)
Small high energy tail→ small background

Accurate and stable beam pointing is important(Keep the peak energy stable)
2011年7月20日水曜日

14

Monitor beam direction and intensity

Near Neutrino Detectorptarget/Horn

Decay volume!

Muon
detector

Near
Detector
off-axis (2.5°)

proton!"Off-axis

on-axis

π→μν
0m

118
110 m

280 m

295 km(to keep the peak energy at SK stable δE<2%)• Muon monitor- monitor spill-by-spill•On-axis INGRID- monitor actual ν beam day-by-day- detector coverage is 10m x 10m

14m

On-axisStability of beam direction should be <1mrad

2011年7月20日水曜日

Far Detector
Near(Super-K)
Detectors

ν beam17.5m
September 22nd, 2006

NNN2

15

Stability of beam direction should be <1mrad(to keep the peak energy at SK stable δE<2%)ν beam stability
3URILOHFHQWHU>FP@

Stability of ν beam direction (INGRID)

Stability of ν interaction rate normalizedby # of protons (INGRID)

68;FHQWHU<FHQWHU
PUDG

INGRID ν int. rate stabilityRun 1+2 / Run 1 < 1%




1'

-DQ

)HE 0DU



$SU

0D\

-XQ

'HF

0
 DU)HEν beam dir. stability < 1mrad
Stability of beam direction (Muon monitor)

2011年7月20日水曜日

Beam dir. stability < 1mrad

17

Off-axis Near Detector (ND280)• 0.2 T UA1 magnet• Fine Grained Detector (FGD)- scintillator bars target (water target in FGD2)- 1.6ton fiducial mass for analysis!"#$%&'()%#"*+&,$-"../%"+*&0%3(&456&789(#"2(• Time Projection Chambers (TPC)- better than 10% dE/dx resolution
momentum resolution at 1GeV/c- 10%
ND280 event displays: ! candidates:/#;&</#%=>?*"@A&+1&4+#+*%+B&C+#;&?*
1+#&%3(&456&E+../F+#/%"+*

ND280 off-axis event gallery
Energy Loss (keV/cm)

νμ CC events rate measurement
dE/dx official plots
in present analysis
5

muons
electrons
pions
protons

4.5
4

14
12

3

TPC2

TPC1

16

!µ"

νμ

8

2
1.5

6

1

4

dE/dx (TPC: data)

sand muon + DIS candidate200

2011年7月20日水曜日

400

600

800

1000

1200

1400

1600

1800

2000

p (MeV/c)

2
0

TPC3

!µ

10

2.5

0

Event display (data)

18

3.5

0.5

3

!
FGD1

µ"

FGD2

quasi-elastic candidate18

body kinematics)



Un-oscillated QP
P
QP
neutron22.5kt fid. vol.
(2m from wall)
Etotal=~4.5MeV
energy threshold
SK-I: April 1996~
Water Cherenkov detector w/ fiducial
SK-IV is runningvolume 22.5kton (Total 50kton)

Far detector (Super-K)

Ikeno-yama

Tlproton•SK
IV w/ Dead-time less DAQ• Phasesystem since September 2008
PMT: ~11100(SK-II)!" (SK-I,III,IV), ~5200 •T2K event trigger by accelerator beamD) PMT: 1885
timing1km

Kamioka-cho, Gifu (2700mwe)
Univ. of Tokyo
Japan
3km
2km 
MC

011/3/11

Mozumi

15

Atotsu3• atmospheric ν samples as control
17

XIV International Workshop on Neutrino Telescopes (2011)39.3 m42
m
C Scientific American

17samples to study detector performance.

11,129 x 20inch PMTs (inner detector, ID)
2011年7月20日水曜日

19

GPS Timing Synchronization
and Beam Event Selection• “REALTIME” beam event selection has been applied.
• GPS Timing Accuracy < 150ns
2011年7月20日水曜日

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Electron-like andmuon-like event at SK

C nCν e latioumsiSuper-Kamiokande IV

Run 999999 Sub 0 Event 209
10-02-17:16:23:39

Inner: 3136 hits, 6453 pe
Outer: 3 hits, 2 pe
Trigger: 0x03

D_wall: 1218.7 cm

e-like, p = 701.5 MeV/c

Charge(pe)>26.7
23.3-26.7
20.2-23.3
17.3-20.2
14.7-17.3
12.2-14.7
10.0-12.2
8.0-10.0
6.2- 8.0
4.7- 6.2
3.3- 4.7
2.2- 3.3
1.3- 2.2
0.7- 1.3
0.2- 0.7< 0.2

Particle identification using
ring shape & opening angle

e-like1300
0 mu-edecays

1040
780
520
260
0
0

500

1000

1500

2000

Times (ns)atmospheric ν data
MCSuper-Kamiokande IV

C nCν μ latiousim

Run 999999 Sub 0 Event 454
10-02-15:01:25:39

Inner: 2208 hits, 9333 pe
Outer: 10 hits, 9 pe
Trigger: 0x03

D_wall: 1479.4 cm
mu-like, p = 1154.7 MeV/c

Charge(pe)>26.7
23.3-26.7
20.2-23.3
17.3-20.2
14.7-17.3
12.2-14.7
10.0-12.2
8.0-10.0
6.2- 8.0
4.7- 6.2
3.3- 4.7
2.2- 3.3
1.3- 2.2
0.7- 1.3
0.2- 0.7< 0.2

μ-like860
0 mu-edecays

688
516
344
172
0
0

500

1000

Times (ns)2011年7月20日水曜日

1500

2000

Probability that μ is mis-identified
as electron is ~1%
21

Search	  for	  νe	
  appearance

2011年7月20日水曜日

22

Analysis overview
1. Apply νe selection criteria to the events at far detector (SK)
2. Compare # of observed events and # of expected events→ search for νe appearance

Contents in this section✤ νe selection✤ The expected number of events at Far detector✤ Systematic uncertainty✤ Results
2011年7月20日水曜日

23✤ νe selection✤ The expected number of events at Far detector✤ Systematic uncertainty✤ Results

2011年7月20日水曜日

24

T2K Signal & Background for νe appearance

νe
sim CCulationSuper-Kamiokande IV•

Run 999999 Sub 0 Event 209
10-02-17:16:23:39

Signal = single electron event- oscillated ν interaction :νeOuter: 3 hits, 2 pe
Trigger: 0x03
D_wall: 1218.7 cm
e-like, p = 701.5 MeV/c

Charge(pe)eνμInner: 3136 hits, 6453 pe

e

>26.7
23.3-26.7
20.2-23.3
17.3-20.2
14.7-17.3
12.2-14.7
10.0-12.2
8.0-10.0
6.2- 8.0
4.7- 6.2
3.3- 4.7
2.2- 3.3
1.3- 2.2
0.7- 1.3
0.2- 0.7
< 0.2

e
1300
0 mu-edecays

1040
780

p

520
260
0
0

500

1000

1500

2000

Times (ns)

CCQE : νe + n → e + p(dominant process at T2K beam energy)

Super-Kamiokande IV
Run 999999 Sub 0 Event 458!

10-02-15:01:36:54
Inner: 3366 hits, 8116 pe0!
"#Outer: 7 hits, 5 pe

Trigger: 0x03

D_wall: 1443.6 cm

e-like, p = 898.6 MeV/c• Background- π from NC interaction- intrinsic ν in the beam (from μ, K
0edecays)Charge(pe)small opening
angle

!

>26.7
23.3-26.7
20.2-23.3
17.3-20.2
14.7-17.3
12.2-14.7
10.0-12.2
8.0-10.0
6.2- 8.0
4.7- 6.2
3.3- 4.7
2.2- 3.3
1.3- 2.2
0.7- 1.3
0.2- 0.7
< 0.2

π0→γγ

NC
sim 1π 0
ula
tio
n

1400
0 mu-edecays

1120
840
560
280
0
0

500

1000

1500

2000

Times (ns)2011年7月20日水曜日

25

νe selection at far detector (SK)The selection criteria were optimized for initial running condition
7 selection cuts

The selection criteria were fixed before data taking started to avoid bias

1. T2K beam timing & Fully contained (FC)(synchronized the beam timing, no activities in the OD)
2. In fiducial volume (FV)
(distance btw recon. vertex and wall > 200 cm)
3. Single electron(# of ring is one & e-like)
4. Visible energy > 100 MeV
5. No decay electron observed(no delayed electron signal)
6. Reconstructed invariant mass (Minv) < 105 MeV/c2
7. Reconstructed neutrino energy (Erec) < 1250 MeV
2011年7月20日水曜日

26

1.Beam timing and FC cut• Events in the T2K beam timing synchronized

OD
FV
ID

by GPS

Clear beam structure !

10

10

LE: low energy events
OD: hits at Outer Detector
3 FC: No hit at Outer Detector

LE

OD

2

FC

10

BG (atmν)
expectation 1.9

1

Number of events / 40nsec

Number of events / 20!sec

relative event timing to the spill timing

10

5

0

-500

-250

0

6T0 (!sec)

250

500

Run 1
Run 2

15

-1000 01000 2000 3000 4000 5000

6T0 (nsec)

ΔT0 = TGPS@SK - TGPS@J-PARC - TOF(~985μsec)
2011年7月20日水曜日

27

!7J(L(J-D%C@M?(2"!J:(,86J(J"J?(L(C-@(,86J(J"C?OD(L(@(!"#$"%

2. Fiducial volume cut
FV(distance between
recon.
vertex&''()*$*(+,-(.,/-(01(and wall > 200cm)(((((((((((((((((((((((2345(6.#7*'89"):
;1<(=+8,>?@0"!<(ABCDE@/7;!

2011年7月20日水曜日;!

01(#",/*'")(NO(%(C-@ID;1<(=+8,>?@0"!<(FGFBCHC@/7

;!

28

Data
Osc. ie CC
i!+i! CC
ie CC
NC

40

(MC w/
sin22θ13 = 0.1)

20

0Number of events

Number of events

3. Single electron cut (# of ring is one & e-like)

10

2

3

4

Number of rings

2011年7月20日水曜日*5

μ-likee-like
5

0

1

Data
Osc. ie CC
i!+i! CC
ie CC
NC
(MC w/
sin22θ13 = 0.1)

-10

0

10

PID parameter29

4. Visible energy > 100 MeV(visible energy = electron-equivalent energy
deposited in ID)

4

e

Data
Osc. ie CC
i!+i! CC
ie CC
NC

3

T2K MCsin22θ13 = 0.1

2

this cut rejects 14% of
NC, 30% of νμ CC bkg.
98% of signal remains
with this cut

1

0

0

1000

2000

Visible energy (MeV)2011年7月20日水曜日* Reject events with muons or pions
which are invisible or
mis-identified as electron mis-id
as e(νμ events orμ
CC non-QE events)

3000

Number of events

Number of events /(100 MeV)

* Reject low energy events, such as
NC background and decay
electrons from invisibleμmuon decays

5. No decay electron observed(no delayed electron signal)e

DataOsc. ie CC
i!+i! CC
ie CC
NC

10

T2K MCsin22θ13 = 0.1

this cut rejects
85% of νμ CC bkg.
90% of signal remains
with this cut

5

0

0

1

2

3

4

*5

Number of decay-e
30Super-Kamiokande IV

6. Reconstructedinvariant mass (Minv) < 105 MeV/c2

Run 999999 Sub 0 Event 458
Inner: 3366 hits, 8116 pe
Outer: 7 hits, 5 pe0!
"#
Trigger: 0x03

D_wall: 1443.6 cm
e-like, p = 898.6 MeV/c

Charge(pe)* Suppress NC π0 backgroundNumber of events /(15 MeV/c2)

Forced to find 2nd ring by using expected lightpattern under the 2 e-like rings assumption, andthen reconstruct invariant mass of these 2 e-like
rings

5

!

10-02-15:01:36:54

small opening
angle

!

>26.7
23.3-26.7
20.2-23.3
17.3-20.2
14.7-17.3
12.2-14.7
10.0-12.2
8.0-10.0
6.2- 8.0
4.7- 6.2
3.3- 4.7
2.2- 3.3
1.3- 2.2
0.7- 1.3
0.2- 0.7
< 0.2

π0→γγ

NC
sim 1π 0
ula
tio
n

1400
0 mu-edecays

1120
840
560
280

Data
Osc. ie CC
i!+i! CC
ie CC
NC

4

0
0

500

1000

1500

2000

Times (ns)T2K MC3

sin22θ13 = 0.1

this cut rejects 71% of
NC background
91% of signal remains
with this cut

2
1
0

0

100

200

2

300

Invariant mass (MeV/c )2011年7月20日水曜日

31

7. Reconstructed energy (Erec) < 1250 MeV* Reject intrinsic beam νe backgrounds at high energyν* Signal (νμ→νe) has a sharp peak at Eν~600MeV

e(pl,θl)p

Number of events /(250 MeV)

reconstruct energy assuming CCQE
DataOsc. ie CC
i!+i! CC
ie CC
NC

3

T2K MCsin22θ13 = 0.1

2

this cut rejects 36%
of beam νe bkg.
98% of signal remains
with this cut

1

0

0

1000

2000

Erec =

mn El − m2l /2 − (m2n − m2p )/2
mn − El + pl cos θl(with additional correction for nuclear potential)

After all the selection criteria
background rejection :>99% for νμ CC,
77 % for beam νe CC,
99 % for NCνμ→νe CC signal eff. : 66 %3000

Reconstructed i energy (MeV)2011年7月20日水曜日

32✤ νe selection✤ The expected number of events at Far detector✤ Systematic uncertainty✤ Results

2011年7月20日水曜日

33

Expected # of events at Far detector
exp
NSK

=

µ, Data
RN D

×

MC
NSK
µ, M CRN D

ND νμ event rate
Measurement of the number of inclusive νμ charged-current events in
ND per p.o.t. using data collected in Run 1 (2.88 x 1019 p.o.t.)
Stability of the beam event rate is confirmed by INGRID measurement
INGRID ν int. rate stability Run 1+2 / Run 1 < 1%

F/N ratio for νe signal event
MCNSKνe sig.
µ, M C
RN
D
2011年7月20日水曜日=

�(flux ) x (osc. prob.) x (x-section) x (efficiency) x (det. mass)ΦSKνµ (Eν ) · Pνµ →νe (Eν ) · σ(Eν ) · �SK (Eν ) dEν
M SK�· N D · POTSK
M
ND
Φνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν

34

Neutrino flux prediction
T2K Neutrino beam simulation basedon Hadron production measurements

actual beam profile &position(beam monitors meas.)graphitetarget

π, K

�

ΦSK
νµ (Eν ) · Pνµ →νe (Eν ) · σ(Eν ) · �SK (Eν ) dEν�ΦNDνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν

horn focusing,
decay is simulated
by GEANT3

μ(e)

ν

SK

ND

proton beam

2011年7月20日水曜日

35

Neutrino flux prediction
T2K Neutrino beam simulation basedon Hadron production measurements

actual beam profile &position(beam monitors meas.)graphitetarget

π, K

�

ΦSK
νµ (Eν ) · Pνµ →νe (Eν ) · σ(Eν ) · �SK (Eν ) dEν�ΦNDνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEννhorn focusing,
decay is simulated
by GEANT3

μ(e)

SK

ND

proton beam

Hadron production in 30GeV proton + C• Use CERN NA61/SHINE pion measurement(large acceptance: >95% coverage of ν parent pions)• Kaon, pion outside NA61 acceptance, other interactionin the target were based on FLUKA simulation• Secondary interaction x-sections outside the target were based on
experimental data
2011年7月20日水曜日

35

Predicted Neutrino Flux at SK

2011年7月20日水曜日

36

νμ interaction rates at near detector•

Measure # of inclusive νμ charged current interaction (NDataND)
Event display (data)
TPC1

Select events
which have FGD hits andμ-like tracks reconstructedin TPC

μ

TPC2

νμ

TPC3

νμ
FGD1

FGD2

High purity : 90% νμ Charged Current int. (50% CCQE)

2011年7月20日水曜日

37

ND Measurement of muon momentum ininclusive νμ CC events (νμ + N → μ+ + X)
p.o.t. normalized

data is consistent with
MC based on the NA61 andν interaction simulation (w/o tuning)

Resultsµ, Data
RN D= 1529events / 2.9 × 1019 p.o.t.

µ, Data
RN D+0.044=1.036±
0.028(stat.)−0.037 (det. syst.) ± 0.038(phys. syst.)µ, M C
RN D
2011年7月20日水曜日

38

2
The expected number of events for sin 2θ

13=0

The expected number of events with 1.43 x 1020 p.o.t.

NexpSK tot. = 1.5 events

The expected# of events at
SK

beam
νμ CC

beam
νe CC

NC

0.03

0.8

0.6

Oscillated
νμ→νe

Total

(solar term)

0.1

1.5

# of NC background is calculated byexp
NSK
N C bkg.

2011年7月20日水曜日µ, Data
= RN
×
D

MC
NSK
N C bkg.
µ, M CRN
D39

✤ νe selection criteria✤The expected number of events at Far detector✤ Systematic uncertainty✤ Observation at Far detector & Results

2011年7月20日水曜日

40

exp
Systematic uncertainty on N
error source(1) ν flux(2) ν crosssectionint. crosssection(3) Near detector(4) Far detector(5) Near det. statistics
Total

exp
NSK

µ, Data= RN×
Dfor sin22θ13=0

NexpSK=1.5±0.3
eventsMC
NSKµ, M C
RN
D

�
2011年7月20日水曜日

syst. error±8.5%±14.0%+5.6−5.2 %±14.7%±2.7%+22.8−22.7 %SKΦSK
νµ (νe ) (Eν ) · Posc. (Eν ) · σ(Eν ) · �SK (Eν ) dEν�ΦNDνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν

41

exp
Systematic uncertainty on N
error source(1) ν flux(2) ν crosssectionint. crosssection(3) Near detector(4) Far detector(5) Near det. statistics
Total

exp
NSK

µ, Data= RN×
Dfor sin22θ13=0

NexpSK=1.5±0.3
eventsMC
NSKµ, M C
RN
D

�
2011年7月20日水曜日

syst. error±8.5%±14.0%+5.6−5.2 %±14.7%±2.7%+22.8−22.7 %SKΦSK
νµ (νe ) (Eν ) · Posc. (Eν ) · σ(Eν ) · �SK (Eν ) dEν�ΦNDνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν

41

Neutrino flux uncertainty
Uncertainties in hadronproduction and interaction are
dominant sources
Error source• Pion production�

error source(1) ν flux(2) ν cross section(3) Near detector(4) Far detector(5) Near det. statistics
Total

ΦSK
νµ (νe ) (Eν ) · Posc. (Eν ) · σ(Eν ) · �SK (Eν ) dEν�ΦNDνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν

- NA61 systematic uncertainty in each pion’s (p,θ) bin• Kaon production- Used model (FLUKA) is compared with the data(Eichten et. al.) in eachkaon’s (p,θ) bin• Secondary nucleon production- Used model (FLUKA) is compared withthe experimental data

• Secondary interaction cross section

n,p

π, K

proton- Used model (FLUKA and GCALOR) is compared withgraphite target

the experimental data of interaction x-section (π, K and nucleon)

2011年7月20日水曜日

42

Summary of ν flux uncertainties on NexpSK for sin22θ13=0

Error source
Pion production
Kaon production
Nucleon production
Production x-section
Proton beam position/profile
Beam direction measurement
Target alignment
Horn alignment
Horn abs. current
Total

exp
NSK

µ, Data= RN
×Dµ, M C
RN D

MC
NSK

5.7%
10.0%
5.9%
7.7%
2.2%
2.7%
0.3%
0.6%
0.5%
15.4%

6.2%
11.1%
6.6%
6.9%
0.0%
2.0%
0.0%
0.5%
0.7%
16.1%

MC
NSK
µ, M CRN
D

MC
NSKµ, M CRN
D

2.5%
Hadron7.6%
1.4% production& interaction
0.7%
2.2%
0.7%
0.2%
0.1%
0.3%
8.5%

The uncertainty on NexpSK due to the beam flux syst. is 8.5%

2011年7月20日水曜日

43

Summary of ν flux uncertainties on NexpSK for sin22θ13=0

Error source
Pion production
Kaon production
Nucleon production
Production x-section
Proton beam position/profile
Beam direction measurement
Target alignment
Horn alignment
Horn abs. current
Total

exp
NSK

µ, Data= RN
×Dµ, M C
RN D

MC
NSK

5.7%
10.0%
5.9%
7.7%
2.2%
2.7%
0.3%
0.6%
0.5%
15.4%

6.2%
11.1%
6.6%
6.9%
0.0%
2.0%
0.0%
0.5%
0.7%
16.1%

MC
NSK
µ, M CRN
D

MC
NSKµ, M CRN
D

2.5%
Hadron7.6%
1.4% production& interaction
0.7%
2.2%
0.7%
0.2%
0.1%
0.3%
8.5%

The uncertainty on NexpSK due to the beam flux syst. is 8.5%
Error cancellation works for some beam uncertainties
2011年7月20日水曜日

43

FIG. 2. Beam centering stability as measured by INGRID.

ν int. cross section uncertainty

error source(1) ν flux(2) ν cross section(3) Near detector(4) Far detector(5) Near det. statistics
Total

coherent pion production (CC coherent π 0 ), and others.
For NC interactions, they are NC 1π 0 , NC coherent π
Evaluate
uncertainty
on F/Nbynorvarying theandothers. Eachreaction is assigned
an ratio
absolute�malization error, see Table I. Uncertainties include variSK
cross
sectionwithinits
uncertainty
Φation of the axial mass by ±0.2 GeV for QE and single νµ (νe ) (Eν ) · Posc. (Eν ) · σ(Eν ) · �SK (Eν ) dEν�pion production events, and ±0.5 GeV for coherent pion
ND
Cross
sectionuncertaintiesareΦνµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν
processes. The CCQE error increases at lower energies
estimated
Data/MCbetween
comparison,to accountforby
diﬀerences
near and far detecCC QE in SciBooNE
comparisonand parameter
torsmodel
nucleartargets. Uncertainties
in intranuclear final
Preliminary
variation
stateinteractions (FSI), implemented with a miroscopic
cascade model [28], introduce an additional error in thesection uncertainty
rates, seeCross
e.g. [29].
relative to the CCQE total x-section

cm2
GeV/c"nucleon-39

d#/dp!0

Process
Systematic error (comment)
CCQE
energy dependent (∼ ±7% at 500 MeV)
CC 1π
30% (Eν < 2 GeV) – 20% (Eν > 2 GeV)
CC coherent π 0100% (upper limit from [30])CC other
30% (Eν < 2 GeV) – 25% (Eν > 2 GeV)
NC 1π 030% (Eν < 1 GeV) – 20% (Eν > 1 GeV)
NC coherent π
30%
NC other π
30%
Final State Int. energy dependent (∼ ±10% at 500 MeV)

1.5

MiniBooNE data
MC (NEUT)

1

0.5

0
0

Uncertaintyof σ(ν )/σ(νμ) = errors±6% for cross-sections.
TABLE I. Assumed esystematic

0.5

1

1.5

p [GeV/c]
Pπ0 (GeV/c)
!0

Error

2011年7月20日水曜日

2 $10

2.5

44

ν int. cross section uncertainty
exp
2
on N SK for sin 2θ13=0

error source(1) ν flux(2) ν cross section(3) Near detector(4) Far detector(5) Near det. statistics
Total

Main ν interaction in each event

Error source
SourceCC QE shape
CC 1π
CC Coherentπ
CC Other
NC 1π 0NC Coherentπ
NC Otherσ(νe )
FSI
Total

exp
syst. error on NSK
3.1%
2.2%
3.1%
4.4%
5.3%
2.3%
2.3%
3.4%
10.1%
14.0%

NC background : NC1π0
Beam νe background : νe CCQE
Signal : νe CCQE
ND CC event : CCQE(50%)
CC1π(23%)

Uncertainty in pionʼs
final state interaction
is dominant

The uncertainty on NexpSK due to the ν x-section syst. is 14% (sin22θ13=0)
2011年7月20日水曜日

45

Far detector uncertainty�SKΦνµ (νe ) (Eν ) · Posc. (Eν ) · σ(Eν ) · �SK (Eν )�error source(1) ν flux(2) ν cross section(3) Near detector(4) Far detector(5) Near det. statistics
Total

dEν

ΦND
νµ (Eν ) · σ(Eν ) · �N D (Eν ) dEν

• Uncertainty due to the SK detector systematics• Evaluate using various control sample

2011年7月20日水曜日

46

2500

0
Uncertainty of NC π rejection
2000
1500
1000

500

Topological control sample of π0
0
-15
-10
-5
0
5
10
15
PID likelihood
made by combining one data electron +one simulated γ
Figure 4: PID likelihood of the primary h-π0 samples along the event selectio
Normalized by number of events

apply T2K νe selection and compare
The MC distribution is normalized to data by entries. The statistical error fro
cut inefficiency
the electron datatheis shown
each bin. Thebetween
cut thresholdcontrol
is indicated by the pi
arrow.
sample data and its MC→ difference is assigned as sys. error
Primary h-/0 Data
Primary h-/0 MC

control sample data

3000

MC

2500
2000
1500
1000
500
0

50

100

Normalized by number of events

150

200
250
300
POLfit inv. mass [MeV]

invariant mass Minv [MeV]0
π efficiency=6.8±0.7(syst.)%Figure 5: POLfit π0 mass for the primary h-π0 samples along the event selectio
2011年7月20日水曜日

The MC distribution is normalized to data by entries. The statistical error fro
the electron data is shown in each bin. The cut threshold is indicated by the pi
47

Uncertainty of νe CCQE selection efficiency
detection efficiency of νe CC (for dominant BG and signal)

atmospheric ν sample

subsample which satisfies all T2K νe selection criteria (signal-like)and sidebands
signal-like(1-ring)signal-like(e-like)sideband-A(μ-like)
PID parametersignal-likesideband-B(multi-ring)

sideband-C

Ring Counting Parameter

Invariant mass

From comparisons btw the atmν data and MC,
we constrain selection efficiency of each cuts.
(syst.)(syst.)(syst.)
2011年7月20日水曜日(syst.)(syst.)(syst.)
48

Particle ID uncertainty study!"#$%!&µ''()*+&,*-./01!2

5;=;'
>?

/&6%7/

atmospheric ν sample

μ control sample selected by decay electrons
Number of Events

Cosmic ray μ sample

6050

i µ CC QE
i i CC non-QE
i e CCNC

40
30

e-like20
10345'6%7/6%8""9':;<;$/=/<
mis-PID:
Data: 0.00±0.16(stat.)%
MC : 0.10±0.10(stat.)%

0
-15

-10

-5

0

5

10
15
PID Likelihood

mis-PID:
Data: 0.54±0.39(stat.)%
MC : 0.20%

The mis-ID fraction and the likelihood are well reproduced.
→PID uncertainty < 1%2011年7月20日水曜日

49

Summary of Far detector systematics uncertaintyMCδNSKνe sig.

MC
δNSK
bkg. tot.

MCNSK
νe sig.

MC
NSK
bkg. tot.

π0 rejection

-

3.6%

Ring counting

3.9%

8.3%

Electron PID

3.8%

8.0%

Invariant mass cut

5.1%

8.7%

Fiducial volume cut etc.

1.4%

1.4%

Energy scale

0.4%

1.1%

Decay electron finding

0.1%

0.3%

-

1.0%

7.6%

15%

Error source

Muon PID

Total

2011年7月20日水曜日

50

Total Systematic uncertainties
Summary of systematic uncertainties on NexpSK total. for sin22θ13=0 and 0.1
Error source(1) Beam flux(2) ν crosssectionint. crosssection(3) Near detector(4) Far detector(5) Near det. statistics
Total

sin2 2θ13 = 0±8.5%±14.0%+5.6−5.2 %±14.7%±2.7%+22.8−22.7 %

NexpSK tot. = 1.5 ± 0.3
2011年7月20日水曜日

sin2 2θ13 = 0.1±8.5%±10.5%+5.6−5.2 %
±9.4%
±2.7%
+17.6
−17.5 %

cf.
sin22θ13=0:#sig = 0.1 #bkg = 1.4
sin22θ13=0.1:#sig = 4.1 #bkg = 1.3

at sin22θ13=051

Total Systematic uncertainties
Summary of systematic uncertainties on NexpSK total. for sin22θ13=0 and 0.1
Error source(1) Beam flux(2) ν crosssectionint. crosssection(3) Near detector(4) Far detector(5) Near det. statistics
Total

sin2 2θ13 = 0±8.5%±14.0%+5.6−5.2 %±14.7%±2.7%+22.8−22.7 %

sin2 2θ13 = 0.1±8.5%±10.5%+5.6−5.2 %
±9.4%
±2.7%
+17.6
−17.5 %

cf.
sin22θ13=0:#sig = 0.1 #bkg = 1.4
sin22θ13=0.1:#sig = 4.1 #bkg = 1.3(due to small Far det.
uncertainty for signal)

NexpSK tot. = 1.5 ± 0.3
2011年7月20日水曜日

at sin22θ13=051

✤ νe selection✤The expected number of events at Far detector✤ Systematic uncertainty✤ Results

2011年7月20日水曜日

52

Number of events /(250 MeV)

The expected# of events at
SK

Oscillated
νμ→νe

beam
νμ CC

beam
νe CC

NC

0.03

0.8

0.6

Data
Osc. ie CC
i!+i! CC
ie CC
NC

3

T2K MC

Total(solar term)

0.1

1.5

Expected # of events @ θ13=0
Nskexp=1.5±0.3

sin22θ13 = 0.1

2

Observed # of events
obs
Nsk = 6

1

0

0

1000

2000

3000

Reconstructed i energy (MeV)2011年7月20日水曜日

53

νe candidate events

2011年7月20日水曜日

54

2011年7月20日水曜日

55

2011年7月20日水曜日

56

2011年7月20日水曜日

57

2011年7月20日水曜日

58

2011年7月20日水曜日

59

2011年7月20日水曜日

60

Further check
Check several distribution of νe candidate events
Data
Osc. ie CC
i!+i! CC
ie CC
NC

e
θbeam
Beam direction

Number of events

3(MC w/
sin22θ13 = 0.1)

2

1

0

-1

-0.5

0

0.5

1

cos ebeam
2011年7月20日水曜日

61

Vertex distribution of νe candidate events
2000

2000

beam direction

1000

Vertex Z (cm)Vertex Y (cm)

1000

0

0

-1000

-1000

-2000
-2000

-2000

-1000

0

1000

2000

Vertex X (cm)

Events tend to cluster at large R→ Perform several checks. for example

0

1000

2

2000
2

Vertex R (cm )

3000
3
x 10

Event outside FV* Check distribution of events outside FV → no indication of BG contamination* Check distribution of OD events → no indication of BG contamination* A K.S. test on the R2 distribution yields a p-value of 0.03
2011年7月20日水曜日

62

Results for νe appearance search
20
with 1.43 x 10 p.o.t.
The observed number of events is 6
The expected number of events is 1.5 ± 0.3
for sin22θ13=0→ Probability to observe 6 or more events is
0.7%, assuming θ13=0, corresponding to 2.5σ
significance.
2011年7月20日水曜日

63

2
Allowed region of sin 2θ
2
for each Δm

13

23(assuming δCP=0,sin22θ23=1.0)
10-1

10-1

6 m223 < 0|6 m223| (eV2)|6 m223| (eV2)

6 m223 > 0
10-2

10

-3

10-2

10

-3
Best fit to T2K data
68% CL10

90% CL

-4

0

0.2

0.4

0.6

sin22e13

0.8

1

10

-4

0

0.2

0.4

0.6

0.8

1

sin22e13

Feldman-Cousins method was used
2011年7月20日水曜日

64

2
Allowed region of sin 2θ

13for each δCP(assuming Δm223=2.4 x 10-3 eV2)//

6 m223 > 00Best fit to T2K data-//2

6 m223 < 0

//2

bCP

bCP

//2

0

T2K
1.43 !1020 p.o.t.

-//2

68% CL
90% CL

-/

0

0.1

0.2

0.3

0.4

0.5

sin22e13

0.6

-/

0

0.1

0.2

0.3

0.4

0.5

0.6

sin22e13

90% C.L. interval (assuming Δm223=2.4 x 10-3 eV2, δCP=0)0.03 < sin22θ13 < 0.28
2011年7月20日水曜日

0.04 < sin22θ13 < 0.34
65Comparison withMINOS

In signal-enhanced region(LEM>0.7):
Expected background (θ13=0):49.5 +- 2.8 (syst) +- 7.0 (stat)
Observed data:
62
2011年7月20日水曜日

66

T2K Next steps
Aim to establish νe appearance andto determine the angle θ13
This result is obtained by only 2% exposure of T2K’s goal.

• Plan for re-starting experiment in this calendar year
- Recovery works in progress• Analysis improvement- New analysis methods using ν signal shape (e.g. recon. energy) are underedeveloping- Improve uncertainties in the Super-K for subdominant BG sources,
i.e. π±, π±π0, μπ0 etc.

2011年7月20日水曜日

67

Conclusion• We reported new results from ν → ν oscillation analysis basedμe

on 1.43 x 1020 p.o.t. (2010 Jan. - 2011 Mar.)- Observe 6 candidate events- # of expected events = 1.5 ± 0.3(syst.) (sin 2θ = 0)
- Under null θ hypothesis, prob. of observing 6 or more events is 0.007,
2

13

13

equivalent to 2.5σ significance.

- 0.03 (0.04) < sin 2θ < 0.28 (0.34) at 90% C.L. for normal (inverted)2

13

hierarchy (assuming Δm223=2.4 x 10-3 eV2, δCP=0, sin22θ23=1.0)

Indication of νμ→νe appearanceThis result was published as Phys. Rev. Lett. 107, 041801 (2011)
Reference: arXiv:1106.1238 for the T2K experimental setup.

• Plan for improve the measurement after recovery of theexperiment in this calendar year•

νμ disappearance result with 1.43 x 1020 p.o.t. data will bereported this summer

2011年7月20日水曜日

68

Backup2011年7月20日水曜日

69

Toward full picture of neutrino
masses and mixings
atmospheric ν

Discovery of (θ23, Δm223)
solar, reactor ν→ (θ12, Δm212)→ θ13 in a few year?
If θ13 is really large (sin22θ13~0.1) as indicated by T2K,
we have to think very seriously how to explore last ν’sparameter in the MNS matrix:

δCP
2011年7月20日水曜日

CP odd term in P(νμ→νe)sinθ12sinθ13sinθ23sinδ
77

x20 Larger Target

Quest for CP Violationin lepton sector.

2011年7月20日水曜日~0.6GeV !µ"295km
Higher Intensity

78Compare electron appearance (number
and spectrum) in ν and anti-ν beami mode400b =0b =1/2/b =/b =<1/2/

400

Events/50MeV

Events/50MeV

600

Total BG

200

iµ/iµ BG
0
0

1

200
Total BG100
02

Eirec (GeV)

Events/50MeV

b =1/2/b =/b =<1/2/

50
0
-50
-100

1

2

Eirec (GeV)
b =1/2/b =/b =<1/2/

100
50
0
-50

-100
1

Eirec (GeV)2011年7月20日水曜日

0iµ/iµ BG

150

100

-150
0

b =0
b =1/2/b =/b =<1/2/300

150

Events/50MeV

diff. from
δ=0 case

νe candidates

i mode

2

-150
0

1

2

Eirec (GeV)
79

Sensitivity on δCP
Hyper-K (540kt FV) / 1.5yrs i + 3.5yrs i /1.66MW

1

b [/]

1m
2m
3m
0

T2K @
90%CL
-1
0

0.06 0.08
0.1
0.12
sin22e13
5 years (1.1yrs ν beam and 3.9yrs anti-ν beam )assuming 5% uncertainties for signal, νμ BG, νe BG, and νe/anti-νe.
2011年7月20日水曜日

0.02

0.04

80

CPV discovery potential
CP δ value for which we can exclude CP conserving hypothesis.
1

b [/]

5m
3m

0

>5σ

Hyper-K (540kt FV)
1.5yrs i + 3.5yrs i
1.66MW>5σ
Normal hierarchy

-1 -3
10

2011年7月20日水曜日

10-2

10-1

sin22e13

T2K @90%CL
81Proton Decay
u
u
d

p
20
18
16

- explore quark/lepton unification +!
p!e+!0
e!

X

d

d

!0

Proton mass resolution =3%

14

p!"K+
• 3.3 x 1033 years (Super-K I+II+III @ 90%C.L.)! 2 x 1034 years (0.54 Mton x 10yrs @ 90% CL)

12
10
8
6
4
2
0
750

• 1.0 x 1034 years (Super-K I+II+II @ 90% C.L.)! 1 x 1035 years (0.54Mton x 10yrs @ 90% CL)

800

850

900

950

1000 1050 1100

proton invariant mass (MeV/c2)

Hyper-K

Hyper-K

2011年7月20日水曜日

82

Pre

r
a
n
il mi

n
g
i
s
e
D
y
8’’ and 13’’ HPDs available in 2012! Hamamatsu will release in 2012

Hyper-K Base-Design!
•
•
•
•
•

Hiroyuki Sekiya NNN10 Dec 15 2010@Toyama

20” PMT w/ cover

1Mton total volume, twin cavity!
0.54Mton fiducial volume!
Inner (D43m x L250m) x 2!
Outer Detector >2m!
Photo coverage 20% (1/2 x SK)• Base-design to be
optimized!
• Geological survey ofthe site is going on!
• Qualitative studies on
physics potential !

2011年7月20日水曜日

18

FEM analysis(Factor of safety)

83