NOON2004 Feb.11-15 Recent K2K Results Tokyo · Recent K2K Results Takanobu Ishii (KEK IPNS) for the...
Transcript of NOON2004 Feb.11-15 Recent K2K Results Tokyo · Recent K2K Results Takanobu Ishii (KEK IPNS) for the...
Recent K2K ResultsTakanobu Ishii (KEK IPNS)
for the K2K collaboration
NOON2004 Feb.11-15Tokyo
K2K Collaboration• JAPAN: High Energy Accelerator Research Organization (KEK)
Institute for Cosmic Ray Research (ICRR), University of TokyoKobe University / Kyoto University
Niigata University / Okayama University Tokyo University of Science / Tohoku University
• KOREA: Chonnam National UniversityDongshin University / Korea University
Seoul National University• U.S.A.: Boston University / University of California, Irvine
University of Hawaii, ManoaMassachusetts Institute of Technology
State University of New York at Stony BrookUniversity of Washington at Seattle
• POLAND: Warsaw University / Solton Institute
Since 2002• JAPAN: Hiroshima University, Osaka University
• CANADA: TRIUMF / University of British Columbia• EUROPE: Rome / Saclay / Barcelona / Valencia / Geneva
• RUSSIA: INR-Moscow
Contents
1. Introduction2. Beam and Detectors3. Data accumulation (K2K-I + K2K-II)4. Oscillation analysis (K2K-I)5. Search for νe appearance (K2K-I)6. New near detector (SCIBAR)7. Summary
1. Introduction• K2K is the first accelerator-based long-baseline neutrino
oscillation experiment to investigate the neutrino oscillation observed in atmospheric neutrinos.
KKEKEK--12GeV PS12GeV PS
SuperSuper--KKamiokandeamiokande
~1%50 %νe /νµ
> 2・10-3 eV210-1 ~10-4eV2∆m2
~ 1.3GeV0.1~100GeVEν
250km(fix.)10~104kmL
K2KAtm.-ν
P(νµ→νX) =
sin22θ・ sin2(1.27∆m2L/EEνν)
L=250 kmL=250 km
•• Do Do ννµ µ events decrease ?events decrease ?•• Is Is EEνν spectrum distorted ?spectrum distorted ?
•• Does Does ννee appear ?appear ?
2. Beam and Detectors
PS: 12GeV proton1.1µsec spill/2.2sec6x1012protons/spill
P ion Monitor
200m
p+Al π+ µ+ + νµe++νe (1.3%) +νµ (0.5%)
Near Detectors
Pion Monitor
MuonMonitor
Neutrino Beam Production
Muon range detector
K2KK2K--II From Mar.1999 ~ Jul.2001Near neutrino detectorsNear neutrino detectors
39m
41.4
mSuperSuper--KamiokandeKamiokande II
Outer detector
Inner detector
1885 8” PMTs
11146 20” PMTs
K2KK2K--IIaIIaAfter the successful resume of the experiment After the successful resume of the experiment Dec.21,2002~Dec.21,2002~
SuperSuper--KamiokandeKamiokande IIIIInner detector
~5200 PMTs with FRP+Acrylic coverRemove Lead Glass detectorto explore lower energy region
NNear neutrino detectorsear neutrino detectors
SciBar detector
K2KK2K--IIbIIbUpgraded near neutrino detectorsUpgraded near neutrino detectors
Oct.3,2003~Oct.3,2003~
Detectors
MRD
1KT
Delivered P.O.T. Delivered P.O.T. (since March 1999)
12/21
5~6x1012 (ppp)
1/16
10/76/23
1999 2000 2001
20032003
K2KK2K--II
20022002
K2KK2K--IIII12/23
8.4x10199.5x1019Total
1.3x10191.5x1019K2K-IIb(-Dec.’03)
2.3x10192.4x1019K2K-IIa
4.8x10195.6x1019K2K-I
AnalysisDelivered
3. Data Accumulation
Neutrino Direction Measured by MRDNeutrino direction isStable within 1 mrad.
99 2000 2001 2003
+- 1 mrad.
-100-80-60-40-20
020406080
100
prof
ile c
ente
r x
(cm
)
-100-80-60-40-20
020406080
prof
ile c
ente
r y
(cm
)
integrated day (1 data point / 5 days)
Neutrino flux MC
Spectrum Stability
Muon energy spectrum stability
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3
99Nov
00Jan
00Feb
00Mar
00May
00June
01Jan
01Feb
01Mar
01Apr
01May
01June
01July
03Jan
03Feb
03Mar
03apr
03May
03June
03Oct
03Nov
Eµ (GeV)
arbi
trar
y un
it
Muon angle distribution stability
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60 70 80 90
99Nov
00Jan
00Feb
00Mar
00May
00June
01Jan
01Feb
01Mar
01Apr
01May
01June
01July
03Jan
03Feb
03Mar
03apr
03May
03June
03Oct
03Nov
θµ (deg.)
arbi
trar
y un
it
Neutrino spectrum was measured by the Pion monitor at the beginning.Spectrum stability is confirmed by the measurements of energy and angle of muons produced in the CC interactions by MRD.
1
10
10 2
10 3
-500 -250 0 250 500
FC
∆(T) µs
even
ts
∆(T) µs
even
ts
0
5
10
15
20
-5 0 5
SK Event Selection
Tspill TSK
GPS
TSpill: Abs. time of spill startTSK: Abs. time of SK eventTOF: 0.83ms (KEK to Kamioka)
sec3.1TOF2.0 µ≤−−≡∆≤− SpillSK TTT
No Decay-eHE Trig.
FC: fully contained (No activity in Outer Detector) FV: 22.5kt Fiducial Volume
Expected Atm. ν BG ~2x10-3 within 1.5µs.
1.5µs
±500µsec
±5µsec
FCFV
72 events
Jun.’99 – Apr.’036.4 x 1019 proton on target
∆T (µsec)
K2K-I + part of K2K-II
Super-Kamiokande Events(Jun.1999~Apr.2003)
FC 22.5kt
POT vs events
KS probability = 64.3%
CT *1018 POT
even
ts
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60
K2KK2K--IIII+16events+16events
K2KK2K--II56events56events
ct diff
FC 22.5kt
mean slope = 1.14/1018POT
fitted slope = 1.17 ± 0.16/1018POT
log likelyhood
CT diff *1018 POT
10-3
10-2
10-1
1
10
0 0.5 1 1.5 2 2.5 3 3.5 4
Event-gap distribution
Spectrum Measurements @ ND
4. Oscillation Analysis (K2K-I)
• 1KT : Pµ<1.5GeV/c, 4π acceptance– 1-ring µ-like(1Rµ) fully contained
in Fid.25ton(FC) : 22,476ev.• SciFi : Pµ>1GeV/c, θµ<60deg.
– 1-track µ-like : 5963ev.– 2-track QE-like (∆θp<25deg.) : 764ev.– 2-track nonQE-like (∆θp>30deg.) : 1288ev.
• PIMON– π (p,θ) distribution ⇒ Neutrino Spectrum (>1GeV)
Fitting ParametersEν : 8 bins, nonQE/QE ratio
SciFi 2 track cos(∆ΘP) distribution
0
100
200
300
400
500
600
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
Data
MC
(CCQE) <25o>30o
cos(∆ΘP)
ν
µ
Pexp.
Pobs.
∆ΘP
Published in PRL 90 (2003) 041801-1
Measured spectrum @ near site
Eν (GeV)
0
1000
2000
3000
0 0.5 1 1.5 2
0
1000
2000
3000
4000
5000
0 50 100 150
Data
MC
MC(QE)
(a)
Pµ [GeV/c]
even
ts / 0
.1 G
eV
/c
(b)
θµ [deg.]
even
ts / 1
0o
0
50
100
150
200
250
0 1 2 3
0
100
200
300
400
0 1 2 3
∆θp < 25o(c)
Pµ [GeV/c]
ev
en
ts /
0.2
5 G
eV
/c
∆θp > 30o(d)
Pµ [GeV/c]
ev
en
ts /
0.2
5 G
eV
/c
Eν spectrum1kt 1Rµ Scifi
2trkQE enriched
2trknQE enriched
Pµ (GeV/c)
Pµ (GeV/c)
Pµ (GeV/c)
Allowed region
Results of the Oscillation Analysis (K2KResults of the Oscillation Analysis (K2K--I)I)Use both Number of events + Spectrum shape
(June ’99 – July ’01) (Nov. ’99 – July ’01)
Null oscillation probability: less than 1%.∆m2=1.5~3.9 x 10-3 eV2 @sin22θ=1(90%CL)
68%90%99%
80.1+6.2-5.4 exp56obs⇔
0
1
2
3
4
5
6
7
8
9
10
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5Eν
rec
Even
ts
Normalized by area
reconstructed Eν
Expectationw/o oscillation
Best FitBest fitpoint2.8x10-3
5. Search for νe Appearance in K2K-I
0
5
10
15
-10 0 10
0
5
10
15
-10 -5 0 5 10
PID (pattern)
(a)
PID (opening angle)
(b)
Fully contained – Single ring – e-like(ring pattern and opening angle)
Visible energy>100MeV – Without decay electrons
Ring pattern
Opening angle
To be submitted for publication
data
νµ MC
NC of νµ MCνe MC
Reduction Summary (νµ νe)DATA SET: June’99 – July’01 (4.8×1019POT)
16 18 18 20 28
signal νe MC (CC)sin22θµe=1 ,
∆m2=2.8x10-3eV2
2.0 2.6 2.9 50 80
νµ MC
0.35 1w/o decay-e
beam νe MCDATA
0.41 1Evis>100MeV
0.42 1PID (e-like)0.48 32Single ring0.82 56FCFV
NC:87% CC1π:7% CCmπ:4% CCQE:2%electron candidate: 1 event observed
2.4 events expected.
10-4
10-3
10-2
10-1
0 0.1 0.2 0.3 0.4 0.5
Results of νµ νe Analysis
sin22θµe
∆m2
(eV
2 )K2K(90%CL)
CHOOZ(90%CL)νe disappearance
SK atm.νallowed (90%CL)
6. New Near Detector (SciBar)
• Extruded scintillator with WLS fiber readout
• Neutrino target is scintillator itself• 2.5 x 1.3 x 300 cm3 cell• ~15000 channels• Light yield
7~20p.e./MIP/cm (2 MeV)• Detect 10 cm track• Distinguish proton from pion by
using dE/dxHigh 2-track CC-QE efficiencyLow non-QE backgrounds
ν
Extrudedscintillator(15t)
Multi-anodePMT (64 ch.)
Wave-lengthshifting fiber
EM calorimeter
1.7m
3m
3m
Just constructed in this summer!
SCIBAR Event DisplayRun 4999, Spill 19016, beam trigger
p
µ
CCQE candidate
3track event
SCIBAR is working well since October 2003
Photo-electrons of SciBar scintillators
Light Yield = 16.52±2.31 p.e./MIP/cm@ 40cm from PMT
(SciBar + MRD) track timing distribution
9-micro-bunch structure is observed
7. Summary•K2K-I data set has been analyzed.
•Reduction of νµ flux together with a distortion of the energy spectrum are observed.
•Probability of non-oscillation is less than 1%.•Oscillation parameters are consistent with those suggested by atmospheric neutrinos.
•Appearance of νe has been searched for.•One candidate event is found, which is consistentwith the background.
•Exclude region is set for the νµ νe oscillation.•K2K-II data taking is going on smoothly.
•Event rate is consistent with K2K-I.•New near detector SCIBAR is working well.•Low energy neutrino data is coming.
Supplement
Pion Monitor
Measure Momentum / Angle Dist.of π’s Just after Horn/Target
+Well known π Decay Kinematics+Well Defined Decay Volume Geometry
⇒PredictνμEnergy Spectrum at Near Site
Far Site
νμ Flux Ratio (Far/Near)as a Function of Neutrino Energy
Ring Image Gas Cherenkov Detector(Index of Refraction is Changeable)
To Avoid Severe Proton Beam Background,νμ Energy Information above 1GeV is Available(β of 12GeV Proton ~ β of 2GeV π)
Muon Monitor
Behind beam dumpsensitive to initially high energy µ (>5.5GeV)
Provide fast (spill-by-spill) monitoring of Intensity targeting/horn stabilityProfile beam direction
Segmented Ionization Chamber
Silicon Pad Detector Array
Muon Range Detector (MRD) as a Neutrino Beam Monitor
100 cm
Run 1244 Spill 20799 TRGID 1 99 6 22 17 48 56 0
Nvtx 0
Large area coverage Vertex DistributionMom. and Angle of Inclusiveμ
High Mass 329ton for r<3mHigh Statistics (~ 5/100pulses)
Good Neutrino Beam Monitor(Stability of Direction, Spectrum and Intensity)
Inclusive Muon
Event Vertex
Neutrino/Fe Charged Current(CC) InteractionFe /Drift tube Sandwich(Fe: 10cm×4+20cm×8)
8m
ΔEμ=150MeV
Beam
Horn and Target System
×20 νFlux Enhancement(Above 500MeV)
Two-horn system operated with 250kA.
To get maximum π collection efficiency,target is embedded in the 1st horn.
1 2 3 4 E ν(GeV)0
Neu
trin
o In
tens
ity
250kA
0kA
0
Near Site νμ Spectrum
Inferred Neutrino Energy Spectrum at Far/Near by Pion Monitor
10 >2.521 (GeV)2 >2.5
Far to Nearνμ Flux Ratio
(GeV)
Simulation is Validated by Pion Monitor MeasurementEvaluation of Far/Near Uncertainty is Based on this Measurement
Pion MonitorSimulation
×10-5
0.1
0.2
0.3
0
Far Site νμ Spectrum0 >2.521 (GeV)
Beam Direction Measured by Muon MonitorMuon Center wasStable within 1 mrad.
99 2000 2001 2002-2003
+- 1 mrad.
Profile comparsion(2000:2001:2003)
Comparison(2000:2001:2003)
Energy spectrum Angle distribution
Allowed regions
Both indicate consistent ∆m2 region
10-4
10-3
10-2
0 0.2 0.4 0.6 0.8 1sin22θ
∆m2 (eV
2)
68%90%99%
10-1
%%
Total no. of Events only Spectrum Shape only
excl.
Comparison with the SK Result
10-4
10-3
10-2
10-1
0 0.2 0.4 0.6 0.8 1
sin22θ
∆m2 (
eV2 )
90%confidencelevel
K2K
SK
10-4
10-3
10-2
10-1
0 0.2 0.4 0.6 0.8 1
sin22θ
∆m2 (
eV2 )
Main Systematic Errors (νµ νe)
• Particle ID– shift likelihood distributions in MC
• +11%−11% in νµ BG• +7%−12% in νe appearance signal
• Ring Counting– shift likelihood distributions in MC
• +15%−13% in νµ BG– compare likelihood of atm.ν DATA
and MC• ±6% in νe appearance signal
• NC Cross Section– change NC cross section within
30%• +20%−25% in νµ BG
0
0.2
0.4
0.6
-20 0 20
K2K νµ MCFCFV elike+X
Evis>100MeVw/o decay-e
Single Ring
20-20
π0
multi-ring likelihood
-10
-5
0
5
10
-10 -5 0 5 10
νµ MC
angle PID
patte
rn P
ID
π0 in K2K-SK
2.0(1.7)
1νe
2.6(2.4)
2π0
80.1(7.7)
56FCFV
νµ MC(NC w/ π0)
DATA
π0 : FCFV & 2 e-like ring & 90<mass<190MeV & Evis>100MeV w/o decay-eνe : FCFV & 1 e-like(tight) ring & Evis>100MeV w/o decay-e
check for amount of π0 production
0
100
200
300
0 100 200 300
150MeV
Reconst. Mass = 119MeV
Reconst. Mass (MeV)
νµ MC
Expectation by νµ MCis consistent withobserved 2 events
K2K status• All detectors working stable. • Trying to update result till next May.• SK-II
– Calibration (PMT, energy scale, water parameter etc.) is on going. – Reconstruction algorithm is being corrected from SK-I.
• 1KT– NC π0 measurement– Improvement on calibration and PID.
• SciFi– Developing PID algorithm and improving tracking.– Study neutrino interaction such as MA and NC.
• MRD– Stability check using off-spill events.
νe appearance– Preparing paper. (Result already shown at a past PAC.)