T2K neutrino oscillation resultsweb.mit.edu/panic11/talks/monday/PARALLEL-1E/1...–Neutrino energy...
Transcript of T2K neutrino oscillation resultsweb.mit.edu/panic11/talks/monday/PARALLEL-1E/1...–Neutrino energy...
T2K neutrino oscillation results
K. Okumura (ICRR Univ. of Tokyo) for T2K collaboration
The 19th Particles and Nuclei International Conference (PANIC 11)
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Contents Introduction ne appearance result nm disappearance result
T2K Collaboration
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International collaboration
(~500 members, 59 institutes, 12 countries)
CanadaU. AlbertaU. B. ColumbiaU. ReginaU. TorontoTRIUMFU. VictoriaYork U.
FranceCEA SaclayIPN LyonLLR E. Poly.LPNHE Paris
GermanyU. Aachen
ItalyINFN, U. BariINFN, U. NapoliINFN, U. PadovaINFN, U. Roma
JapanICRR KamiokaICRR RCCNKEKKobe U.Kyoto U.Miyagi U. Edu.Osaka City U.U. Tokyo
PolandA. Soltan, WarsawH.Niewodniczanski,CracowU. Silesia,KatowiceT. U. WarsawU. WarsawU. Wroclaw
RussiaINR
S KoreaChonnam N. U.U. DongshinSeoul N. U.
SpainIFIC, ValenciaU. A. Barcelona
SwitzerlandETH ZurichU. BernU. Geneva
UKImperial C. L.Lancaster U.Liverpool U.Queen Mary U. L.Oxford U.Sheffield U.STFC/RALSTFC/DaresburyWarwick U.
USABoston U.B.N.L.Colorado S. U.U. ColoradoDuke U.U. C. IrvineLouisiana S. U.U. PittsburghU. RochesterStony Brook U.U. Washington
T2K physics goals
Search for nmne appearance by non-zero q13
– Last unknown mixing angle important for CP phase and mass hierarchy observation
– ~20 times better sensitivity than CHOOZ limit (sin2(2q13)<0.15) expected
Precise measurement of Dm232 and sin2(2q23 )
via nm disappearance
– Expected sensitivity w/ full T2K datasetd(Dm23
2) ~ 1×10-4 eV2, d(sin22q23) ~ 1% (90% C.L.)
~20 times betterthan CHOOZ
2 2 2 2
13 23 13( ) sin 2 sin sin 1.27e
LP m
Emn n q q
D
2 2 2
23 231 sin 2 sin 1.27L
P mE
m mn n q
D
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T2K exp’d sensitivityw/ 3.75 MW x 107 s(90%C.L.)
p
120m0m 280m 295 km
off-axis
Muon monitor
J-PARC 30 GeV
Proton beamSuper-Kamiokande
Near detectors
Decay volume
p nmm
Off-axis (2.5 ˚) nm beam – Intense, low energy narrow-band
– Peak En tuned for oscillation max. ( ~0.6 GeV)
– Reduce BG from high energy tail
– Small ne fraction (~1%)
Muon monitor
T2K overview
Muon monitor– Monitor intensity and profile
spill-by-spill
On-axis detector (INGRID)– Monitor n beam day-by-day
– Detector coverage is 10m x 10m
OA2.5 ˚
INGRID
ND280
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p
120m0m 280m 295 km
off-axis
Muon monitor
J-PARC 30 GeV
Proton beamSuper-Kamiokande
Near detectors
Decay volume
p nmm
Off-axis detector (ND280)– Predict interaction rate w/o oscillation
– 0.2 T UA1 magnet
– Fine grained detector (FGD)
full active for n int. w/ FV 1.6 ton – Time projection chamber (TPC)
Particle ID by dE/dx in gas
Far detector (Super-Kamiokande)– Water Cherenkov detector w/ FV 22.5 kton
– Excellent particle ID for m / e particle with ~99% efficiency
μ-like
e-like
Super-K detector
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m39.3 m
ND280
dE/dx (TPC: data)
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Simulation events
Top view of detector
nm
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Delivered protons for analysis RUN1 (Jan. 2010 ~ Jun. 2010) 3.23 x 1019 p.o.t. achieved in ~50 kW runningRUN2 (Nov. 2010 ~ Mar. 2011) 11.09 x 1019 p.o.t. achieved in ~145 kW running
RUN1+RUN2 total 1.43 x 1020 p.o.t. (2% of final goal)
Stable operation of n beam during this periodDirection stability well within 1mrad. by m mon. and INGRID (dEn<2%)INGRID day-by-day interaction rate is stable
Clear peak of SK events around beam trigger timinglow background (3x10-3% exp’d in FV)
Beam data for analysis
Beam timing of SK events
2 atm n events(1.9 ev exp’d)
n beam dir. stability < 1mrad
Stability of beam direction (Muon monitor)
Stability of n interaction rate normalized by # of protons (INGRID)
Stability of n beam direction (INGRID)
Beam dir. stability < 1mrad
clear bunch structure Run1 Run2
Poster by V. Galymov
ne appearance analysis
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Analysis strategy and selection criteria
Selection Criteria
Beam timing, fully-contained, fiducial volume
Single-ring electron like
Visible energy > 100 MeV
No delayed electron signal
p0 invariant mass (Minv) < 105 MeV/c2
Reconstructed n energy (Enrec) < 1250 MeV/c2
Select single-electron events by oscillated ne CCQE interactions
Main background: intrinsic ne , NC p0 production
Compare # of selected events and expectation at sin2(2q13)=0
Signal (ne CCQE) BG (NC p0 )
Invariant mass cut Reconst. n energy
8Selection criteria are fixed before data analysis
Expected # of events at Super-K
(Dm232 =2.4x10-3 eV2, sin2(2q23)=1.0, dCP=0)
Beam nm CC background
Beam ne CC background
NC background
Oscillated nmne
(solar term)
Total
# of Events 0.03 0.76 0.61 0.09 1.49
Expected number of events at sin2(2q13)=0
exp 1.5 0.3 ( .) eventsSKN syst
,
,
expData
ND
MC
ND
S
MC
SK K
R
RN N
m
m
Expected SK events by Monte Carlo simulation
Calculated by F, s, e, and osc. probability
Summed for beam-nm , ne , anti-nm , and oscillated nmne
Normalization by ND nm event rate
Measurement of # of inclusive nμ charged-current events in ND280
ND280 ne/nm measurement consistent with predicted flux
, , 0.047
0.0371.036 0.028( .) (det . .) 0.038( .)Data MC
ND NDR R stat syst physm m
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ND280 talk by B. Berger2E-3 16:40 today
ne candidate events
All six events by visual examination are consistent with ne CC events
visible energy : 1049 MeV
# of decay-e : 0
p0 Inv. mass : 0.04 MeV/c2
Recon. energy : 1120.9 MeV
6 candidate events observed after all cuts
Null hypothesis (q13=0): 1.5 ±0.3 (syst.) Up fluctuation probability, p-value = 0.7%
corresponding to 2.5 s
Invariant mass Reconst. n energy
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Vertex distribution
out of FV in bottom
Vertex distribution along beam dir.
Check distribution of events outside FV Check distribution of OD events
No indication of BG contamination
Simulation study of beam-induced BG by mis-ID m, p0 photon, neutron, K from outside of ID
very small (3x10-3) events estimated in FV
final sample
FC events
w/o fiducial cut
Vertex of these six events are located near fiducial volume edge
K-S test of R2 event distribution 3% probability
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outsideof FV
Y-X and Z-R2 plots for final events (w/o FV cut)
fiducial volume
(sin2(2q13)=0.1)
(sin2(2q13)=0.1)
Allowed region of sin22θ13 for δCP
(assuming Δm223=2.4 x 10-3 eV2)
0.03 < sin22θ13 < 0.28
sin22θ13 =0.11
0.04 < sin22θ13 < 0.34
sin22θ13 =0.14
90% C.L. interval and best fit (for Δm223=2.4 x 10-3 eV2, sin2(2q23)=1, δCP=0)
Confidence level intervals for sin22θ13 vs δCP
Feldman-Cousins method was used for constructing confidence interval
Normal Inverted
Published in Phys. Rev. Lett. 107, 041801 (2011)12
nm disappearance analysis
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Event selection
Select for nm CC quasi-elastic events – Beam-timing, fully-contained, FV cut
– Single-ring & PID is muonlike
– Reconst. m momentum > 200 MeV/c
– # of delayed electrons ≤ 1
31 events selected after applying cuts– 104 events expected w/o osc
– Neutrino energy reconstructed (Enrec )
with Pm and qbeam
Pmqbeam
m
beam dir.
Pm and cosqbeam dist. for selected events
A selected single-ring m-like event
EventFraction (%)
w/ osc. w/o osc.
nm CC QE 57.2 79.4nm CC non-QE 30.0 15.7NC 6.0 1.6anti-nm 6.3 3.1ne 0.4 0.1
Expected composition w/ osc.
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nm oscillation fitsOscillation fit performed with 2-flavor oscillation assumption
norm shape sys L L L L 2 2log L
2 = -2logL is defined with # of events (Nsk) and Enrec shape
Two independent fits with same inputsFit A : w/ systematic error fittingFit B : w/o systematic error fitting
Feldman-Cousins prescription is used for constructing confidence interval
2 2 21 sin 2 sin 1.27L
P mE
m mn n q
D
Assigned Nsk syst. errors w/ and w/o oscillation Enrec shape syst. errors w/ oscillation
Estimate ~15% w/ oscillation
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Allowed region in (Dm2, sin22q)
(GeV)
Consistent with MINOS/SK results
Reconstructed n energy
Clear oscillation pattern observed
Nu
mb
er o
f Ev
ents
Rat
io
Dm2 (eV2) sin2(2q)
Fit A 2.1 ~ 3.1 x 10-3 > 0.85
Fit B 2.1 ~ 3.2 x 10-3 > 0.84
90% C.L. allowed region sin22q
Dm
2(e
V2 )
Best-fit (Dm2, sin22q) Fit A (2.6x10-3eV2 , 0.99)Fit B (2.6x10-3eV2 , 0.98)
(Fit A)
(Fit B)
Fit A
Fit B
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Summary
First off-axis experimental ne and nm results from T2K, based on RUN1+2 data (1.43x1020 p.o.t.)
Indication of ne appearance consistent with non-zero q13– Observe 6 ne candidate events when 1.5 ± 0.3 (syst.) BG expected at
sin2(2q13)=0 (p-value = 0.7% equivalent to 2.5 s
– 0.03 (0.04) < sin2(2q13) < 0.28 (0.34) at 90% C.L. for normal (inverted) hierarchy (assuming Dm2
23=2.4 x 10-3 eV2, dCP=0)
New result from nm disappearance analysis– Observe 31 events for single-r muon-like ( 104 events expected w/o osc.)
– 90% C.L. allowed region: 2.1x10-3 < Dm2 < 3.1x10-3 eV2, sin22q > 0.85
– Consistent with other nm oscillation results
Resume J-PARC operation in Dec. 2011 and restart T2K data taking as soon as possible
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