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SUMMARY OF θ13 MEASUREMENTS AND PROSPECTS
AAP 2012 meeting, Honolulu Jelena Maricic University of Hawaii October 4, 2012
Executive Summary
Summary of θ13 measurements from reactors 2011-2012 Daya Bay θ13 ~8.7° (~8 σ zero exclusion)
RENO
θ13 ~9.8° (~6 σ zero exclusion)
Double Chooz
θ13 ~9.6° (~3 σ zero exclusion)
Summary of θ13 measurements from beams MINOS T2K
2CP 23
213
213
213
213
213
for δ =0, sin (2θ )=1,
sin (2θ ) = 0.053 at best fit
0.01 < sin (2θ ) < 0.12 at 90% C.L.
sin (2θ ) = 0.094 at best fit
0.03 < sin (2θ ) < 0
normal hierarcy:
inv
.19 at 90% C.L.
sin
erted hierarc
(2θ )
y:
= 0 excluded at 96% C.L.
θ13 ~7° (NH) θ13 ~9° (IH)
θ13 ~9° (NH) θ13 ~10° (IH)
~2 σ zero exclusion
~3 σ zero exclusion
Summary of θ13 measurements
Global fit from Daya Bay, RENO, Double Chooz and T2K:
1
2
3
4
Nσ
Fogli, Lisi, Marrone, Montanino, Palazzo, Rotunno: hep-ph/1205.5254 (2012)
Sin2 θ13 = 0.0241 ± 0.0025 (NH) Sin2 θ13 = 0.0244 ± 0.0025 (IH)
θ13 = 8.9°± 0.9° (~10% relative uncertainty)
Prospects
θ13 measured to be non zero with > 7σ C.L.
In the next 3 years expected to be known with 5% uncertainty
Going from the unknown to the best measured neutrino mixing angle: 2003-2012 But there is more to this measurement…
Outline
Introduction
Review of the experiments
Results of measurement θ13
Prospects
Material adopted from presentations from NOW2012 and ISNP 2012, from members of MINOS, T2K, Double Chooz, Daya Bay and RENO
Introduction
Starting point in 2003: CHOOZ
Last non-measured neutrino mixing angle!
Only the upper limit on the value of angle θ13
was set!
CHOOZ experiment constraint:
(νe → νe disappearance exp)
@∆m2atm = 2.3 10-3 eV2
sin2(2θ13) < 0.15
(90% C.L)
CHOOZ experiment R = 1.01 ± 2.8%(stat)±2.7%(syst)
νe → νx
M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374 M. Apollonio et. al., Eur.Phys.J. C27 (2003) 331-374
θ13 < 11°
θ13 central to fundamental questions CP-violation phase and mass hierarchy
12 12 13 13
12 12 23 23
13 13 23 23
cos sin 0 cos 0 sin 1 0 0sin cos 0 0 1 0 0 cos sin
0 0 1 sin 0 cos 0 sin cos
CP
CP
i
i
eU
e
δ
δ
θ θ θ θθ θ θ θ
θ θ θ θ
− = − × ×
− −
“Solar” θ12 ~ 30° “Atmospheric” θ23 ~ 45° (SK + MINOS)
“Little mixing angle” θ13 < 11° (circa 2011)
(CHOOZ)
Value of θ13 directly influences prospects of
measuring CP violation phase in the weak sector!
θ13 impacts measurements on ~few 100 m scale and above Interesting for nuclear reactor monitoring with neutrinos
Δm221=(7.50+0.19
-0.20)×10-5 eV2
(KamLAND) Δm2
32=(2.32+0.12-0.08)×10-3 eV2
(MINOS)
Hints on θ13 from global fits in 2005/2008
Fogli, Lisi, Marrone, Palazzo, Rotunno: hep-ph/0806.2649v2 (2008)
sin2θ 13 = 0.9+2.3−0.9 × 10−2
Fogli, Lisi, Marrone, Palazzo: hep-ph/0506083 (2005)
sin2 θ 13 = 0.016 ± 0.010
θ13 ~ 5°
θ13 ~ 7°
Large uncertainty and low non-zero exclusion level.
Global fit from KamLAND in March 2011
KamLAND collaboration: hep-ex/1009.4771
sin2 θ 13 = 0.020 ± 0.016
θ13 ~ 8°
Large uncertainty and low non-zero exclusion level.
Review of θ13 experiments
θ13 Measurement Strategies
Use muon neutrinos from accelerator: appearance search for electron neutrinos MINOS T2K
Use electron antineutrinos from nuclear reactor: disappearance search CHOOZ Double Chooz Daya Bay RENO
θ13 and Beam Experiments
MINOS
T2K
T2K uses off-axis beams to achieve: -Increased flux near oscillation max -Reduced high energy NC bkg
νµ
νµ
νe
νe
θ13 and Reactor Experiments
Reactor Near Detector Far Detector
( ) [ ][ ]
∆−=→
MeVm27.1sin2sin1
2312
132
ν
θννE
LmP ee
Eν ~ 4 MeV
(Flux)L2
L ~1.5km
< 14%
No Oscillations
Oscillated
νe νe
High precision measurement required: systematic error ~0.5%
θ13 & Beam Experiments Appearance probability :
dependences in sin(2θ13), sin(θ23), sign(∆m231), δ-CP phase in [0,2π]
θ13 & Reactor Experiments • <Eν> ~ a few MeV only disappearance experiments sin2(2θ13) measurement independent of δ-CP
• P(νe→ νe) = 1 - sin2(2θ13)sin2(∆m231L/4E) + O(∆m2
21/∆m231)
weak dependence in ∆m221
• a few MeV νe + short baselines negligible matter effects (O[10-4] )
sin2(2θ13) measurement independent of sign(∆m213)
Results of measurement θ13 with beams
MINOS Experiment
735 km νµ
MINOS - Main Injector Neutrino Oscillation Search
Two functionally identical detectors to reduce systematics
Near Detector • 1 km from target • 94 m underground, 225 mwe • Measures the energy spectrum and beam composition
Far Detector • 735 km from target • 700 m underground, 2070 mwe • Re-measures the neutrino beam
composition Near Detector
980 tons Far Detector
5,400 tons
Steel/scintillator tracking calorimeters • Alternate orthogonal orientation planes • Steel absorber 2.54 cm thick • Scintillator strips 4.1 cm wide, 1.0 cm thick • 1 GeV muons penetrate 28 layers • Longitudinal sampling = 1.4 radiation lengths • Optical WLS fiber readout to multi-anode PMTs
Detector Technology
Multi-anode PMT
Extruded PS scint. 4.1 x 1 cm
WLS fiber
Clear Fiber cables
2.54 cm Fe
U V planes +/- 450
Magnetized • <B> = 1.3T • Muon energy from
range/curvature • Distinguish μ+ from μ-
tracks
Neutrino Interactions in Detectors tr
ansv
erse
dire
ctio
n
ν e-
µ-
beam direction color scale represents energy deposition
νµ Charged Current νx Neutral Current νe Charged Current
long μ track & possible hadronic activity at vertex
short with compact EM shower profile
short with diffuse shower
120 GeV protons
Focusing Horns
2 m
675 m 15 m 30 m
νµ = 91.7%ν µ = 7.0%
νe +ν e =1.3%
Target
Neutrino mode Horns focus π+, K+
Decay Pipe
π-
π+
νμ
νμ
Monte Carlo
Neutrino Mode
Antineutrino Mode
120 GeV protons
Focusing Horns
2 m
675 m 15 m 30 m
νµ = 91.7%ν µ = 7.0%
νe +ν e =1.3%
Target
Neutrino mode Horns focus π+, K+
Decay Pipe
π+
π-
νμ
νμ
Monte Carlo Monte Carlo Antineutrino mode Horns focus π-, K-
ν µ = 39.9%νµ = 58.1%
νe +ν e = 2.0%
( )ν ν
→ ≈ +
2
2
2 2 312
23 13sin ( )sin ( ) sin m LP
E1.267 Δ
θ θμ e
νe Appearance Measurement
( )eν ν
→ ≈ +
2
2
2 2 3123
213sin ( )sin ( ) sin LP
E1.267 Δm
θ θμ
sensitive to neutrino mixing angle θ13, δCP, mass ordering
( ) ( )if 0, eCP eP P µµδ ν ν ν ν≠ → ≠ → In matter, νe CC scattering modifies oscillation probability ~30% in MINOS
10.6×1020 POT (ν mode)
Electron Appearance in FHC and RHC Beam
3.3×1020 ( ν mode) ν mode Expected (LEM>0.7):
69.1 (background, if θ13=0) 26.0 (signal, if sin2(2θ13)=0.1)
Observe:
88 events
ν mode Expected (LEM>0.7):
10.5 (background , if θ13=0)
3.1 (signal, if sin2(2θ13)=0.1)
Observe:
12 events
Library Event Matching (LEM)
2CP 23
213
213
213
213
213
for δ =0, sin (2θ )=1,
sin (2θ ) = 0.053 at best fit
0.01 < sin (2θ ) < 0.12 at 90% C.L.
sin (2θ ) = 0.094 at best fit
0.03 < sin (2θ ) < 0
normal hierarcy:
inv
.19 at 90% C.L.
sin
erted hierarc
(2θ )
y:
= 0 excluded at 96% C.L.
νe Appearance:ν and ν Combined Contour
● Second generation long-baseline neutrino-oscillation experiment;
● High intensity almost pure νµ beam from Main Ring in J-PARC is shot toward the Super-Kamiokande detector 295km away.
●
from Tokai to Kamioka
● The physics data-taking started in Jan. 2010, and stopped in March 2011 by the earthquake. Resumed almost a year later.
J-PARC in JAEA
Tokai
Tokyo
Kamioka
KEK
T2K experiment
J-PARC in JAEA
Super-Kamiokande J-PARC
Results of measurement θ13 with reactors
Locations
Double Chooz Daya
Bay RENO
Configurations Double Chooz
Daya Bay
300 mwe 115 mwe
1 km 400 m
Reactor Neutrino Detection Signature • Reactors as neutrino sources:
Nν s−1( )= 6NFiss s−1( )≈ 2 ×1011P s−1( )Chooz: P =2x4.25 GWth ⇒Nν~2x1021s-1
Neutrino detection via inverse β decay
Distinctive two-step signature: -prompt event Photons from e+ annihilation Ee = Eν - 0.8 MeV + O(Ee/mn) -delayed event Photons from n capture on dedicated nuclei (Gd) ∆t ~ 30 µs E ~ 8 MeV Gadolinium
Target: Gd doped scintillator 1 g/l Gd in LS
¹ºe + p+ ! e+ + n
The Double Chooz Far Detector Outer Veto (OV) plastic scintillator strips
Outer Steel Shielding 250 t steel (15 cm)
Inner Veto (IV) 90 m3 of scintillator in a steel vessel (10 mm) equipped with 78 PMTs (8 inches)
Buffer 110 m3 of mineral oil in a steel vessel (3 mm) equipped with 390 PMTs (10 inches)
γ-Catcher (GC) 22.3 m3 scintillator in an acrylic vessel (12 mm)
Target 10.3 m3 scintillator doped with 1g/l of Gd compound in an acrylic vessel (8 mm)
~7m
Calibration Glove Box
Daya Bay
θ13 Measurement with DC Far
Interaction Cross-Section
• Recalculations of spectra introduced normalization shift; “anomaly”?
• Th.A. Mueller et al, Phys.Rev. C83(2011) 054615.
• P. Huber, Phys.Rev. C84 (2011) 024617
( )( )
( )∑=
××=
}2,1{Reactors
,2
exp ,4
),(R
Rf
Rf
Rth
R
p tEtE
tPL
NtEN σ
πε
ν
Reference Spectra + Bugey4 “Anchor”
Normalize to Total Rate Measurement of Bugey4
( )( )
( )∑=
××=
}2,1{Reactors
,2
exp ,4
),(R
Rf
Rf
Rth
R
p tEtE
tPL
NtEN σ
πε
ν
Reduces reactor normalization uncertainty
from 2.70% to 1.76%
Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV
Delayed signal Evis = [6.0, 12.0] MeV
Delayed Coincidence Δt = [2, 100] µsec
Require Δt μ > 1 msec
PMT light noise rejection cuts
• PMT hits approx. homogeneous
• PMT hits approx. coincident in time
Multiplicity conditions:
• No extra events around signal
Background rejection:
• No coincident signal in OV
• Require Δt μ > 500 msec if Eμ > 600 MeV
Plus three irreducible backgrounds:
• Accidentals
• Cosmogenic 9Li
• Fast neutrons/stopping muons
Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV
Delayed signal Evis = [6.0, 12.0] MeV
Delayed Coincidence Δt = [2, 100] µsec
Require Δt μ > 1 msec
PMT light noise rejection cuts
• PMT hits approx. homogeneous
• PMT hits approx. coincident in time
Multiplicity conditions:
• No extra events around signal
Background rejection:
• No coincident signal in OV
• Require Δt μ > 500 msec if Eμ > 600 MeV
Preliminary
Trigger efficiency • Threshold at 400keV (ε=50%) • ε=100% above 700keV
Minimum visible energy of ν signal Prompt
energy cut
Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV
Delayed signal Evis = [6.0, 12.0] MeV
Delayed Coincidence Δt = [2, 100] µsec
Require Δt μ > 1 msec
PMT light noise rejection cuts
• PMT hits approx. homogeneous
• PMT hits approx. coincident in time
Multiplicity conditions:
• No extra events around signal
Background rejection:
• No coincident signal in OV
• Require Δt μ > 500 msec if Eμ > 600 MeV
Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV
Delayed signal Evis = [6.0, 12.0] MeV
Delayed Coincidence Δt = [2, 100] µsec
Require Δt μ > 1 msec
PMT light noise rejection cuts
• PMT hits approx. homogeneous
• PMT hits approx. coincident in time
Multiplicity conditions:
• No extra events around signal
Background rejection:
• No coincident signal in OV
• Require Δt μ > 500 msec if Eμ > 600 MeV
Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV
Delayed signal Evis = [6.0, 12.0] MeV
Delayed Coincidence Δt = [2, 100] µsec
Require Δt μ > 1 msec
PMT light noise rejection cuts
• PMT hits approx. homogeneous
• PMT hits approx. coincident in time
Multiplicity conditions:
• No extra events around signal
Background rejection:
• No coincident signal in OV
• Require Δt μ > 500 msec if Eμ > 600 MeV
Neutrino Candidate Selection Prompt signal Evis = [0.7, 12.2] MeV
Delayed signal Evis = [6.0, 12.0] MeV
Delayed Coincidence Δt = [2, 100] µsec
Require Δt μ > 1 msec
PMT light noise rejection cuts
• PMT hits approx. homogeneous
• PMT hits approx. coincident in time
Multiplicity conditions:
• No extra events around signal
Background rejection:
• No coincident signal in OV
• Require Δt μ > 500 msec if Eμ > 600 MeV
• 41% of 9Li BG is rejected by additional muon veto (~5% live-time loss)
• 28% of fast neutron/stop μ BG is rejected by OV anticoincidence
Candidate Rate Variation
Before 9Li reduction cut, no OV anticoincidence applied
Not background-subtracted Rate consistent with expectation
Cross-check: Reconstructed Vertex Position
Events well-localized within target Note: no spatial cuts applied in candidate selection
Detector Calibration
1. PMT and electronics gain non-linearity calibration
LED light injection system
2. Correct for position dependence
Spallation neutron H captures
3. Correct for time stability Spallation neutron Gd captures
4. Energy scale Radioactive sources deployed
into ν-target and γ-catcher
Energy Calibration
Neutron Detection Efficiency Energy & time window, Gd fraction, spill in/out effects • 252Cf source deployed into ν-target and γ-catcher
Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1
Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1
Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1
Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1
Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1
Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1
Preliminary
Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1
Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1
Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1
Backgrounds Accidentals • Prompt: radiation hit on PMT • Delayed: spallation neutron capture • Prevented by radiopurity & shielding • Measured from off-time windows: 0.261 +/- 0.002 day-1
Cosmogenic 9Li • Prompt: beta emission • Delayed: neutrons from long-lived decays • Measured from Δtμ & spatial muon coincidence: 1.25 +/- 0.54 day-1
Fast-n & Stopping muons • Prompt: proton recoil or muon track • Delayed: neutron capture or muon decay • Measured from high-energy spectrum: 0.67 +/- 0.20 day-1
Red: Best-fit Spectrum Grey: Tagged background events White: IBD Signal
Check Rate vs. Reactor Power
2 events observed in 0.84 days livetime with both reactors off (= 2.2 event/day)
→ Background rate consistent with estimation (2.2 ±0.6 event/day)
Best fit to expected rate: sin22θ13 = 0.19 ± 0.06 BG rate = 2.9 ± 1.1 event/day
arXiv:1207.6632
Summary of Rate Uncertainties
Source Uncertainty w.r.t. signal
Statistics 1.1%
Flux 1.7%
Detector
Energy response 0.3%
1.0%
Edelay containment 0.7%
Gd fraction 0.3%
Δt cut 0.5%
Spill in/out 0.3%
Trigger efficiency <0.1%
Target H 0.3%
Background
Accidental <0.1% 1.6% Fast-n + stop μ 0.5%
9Li 1.4%
Summary of Candidates Both Reactors On One Reactor
Pth < 20% Total
Livetime [days] 139.27 88.66 227.93 IBD Candidates 6088 2161 8249
Prediction Reactor B1 ν 2910.9 774.6 3685.5 Reactor B2 ν 3422.4 1331.7 4754.1
9Li 174.1 110.8 284.9 FN & SM 93.3 59.4 152.7
Accidentals 36.4 23.1 59.5 Total Prediction 6637.1 2299.7 8936.8
Data divided into two integration periods based on reactor power Allows use of changing signal/background ratio in fit
Double Chooz Prompt Spectrum
Data w/ Stat. Error Bars
Best Fit Prediction
(w/ Syst. Errors)
Null Oscillation Prediction
Backgrounds
Rate+Shape: sin22θ13= 0.109 ± 0.030 (stat.) ± 0.025 (syst.) χ2/d.o.f. = 42.1/35 Rate-only: sin22θ13 = 0.170 ± 0.035 (stat.) ± 0.040 (syst.) Frequentist analysis: sin22θ13 = 0 excluded at 99.8% (2.9σ) Presented in arXiv:1207.6632, accepted by PRD
RENO θ13 Measurement
Daya Bay θ13 Measurement
Result
Summary and Prospects
Summary of θ13 measurements from beams MINOS T2K
2CP 23
213
213
213
213
213
for δ =0, sin (2θ )=1,
sin (2θ ) = 0.053 at best fit
0.01 < sin (2θ ) < 0.12 at 90% C.L.
sin (2θ ) = 0.094 at best fit
0.03 < sin (2θ ) < 0
normal hierarcy:
inv
.19 at 90% C.L.
sin
erted hierarc
(2θ )
y:
= 0 excluded at 96% C.L.
θ13 ~7° (NH) θ13 ~9° (IH)
θ13 ~9° (NH) θ13 ~10° (IH)
~2 σ zero exclusion
~3 σ zero exclusion
Summary of θ13 measurements from reactors Daya Bay (June 2012) θ13 ~8.7° (~8 σ zero exclusion)
RENO (June 2012)
θ13 ~9.8° (~6 σ zero exclusion)
Double Chooz
θ13 ~9.6° (~3 σ zero exclusion)
Summary of θ13 measurements
Global fit from Daya Bay, RENO, Double Chooz and T2K:
1
2
3
4
Nσ
Fogli, Lisi, Marrone, Montanino, Palazzo, Rotunno: hep-ph/1205.5254 (2012)
Sin2 θ13 = 0.0241 ± 0.0025 (NH) Sin2 θ13 = 0.0244 ± 0.0025 (IH)
θ13 = 8.9°± 0.9° (~10% relative uncertainty)
Energy Spectra Spectral shape
contains some potentially peculiar features when compared to expectation.
Double Chooz
RENO
Daya Bay sin2(2θ13)=0.12
∆m2atm= 3.0 10-3 eV2
Far/Near ratio simulated
Summary and Prospects Better understanding of spectral shape: hint of new
physics?!?
θ13 measured to be non zero with > 7σ C.L. and 10% uncertainty
In the next 3 years expected to be known with 5% uncertainty
Going from the unknown to the best measured neutrino mixing angle: 2003-2012!