Reactor Neutrino Measurement of 13

1
Reactor Neutrino Measurement of ?13
Karsten M. Heeger Lawrence Berkeley National
Laboratory
2
Neutrino Oscillation Parameters
Except for LSND, ?mij2 measured and confirmed.
3
?13 and CP Violation
UMNSP Neutrino Mixing Matrix
atmospheric, K2K
reactor and accelerator
SNO, solar SK, KamLAND
0???
tan2 ?13 lt 0.03 at 90 CL
?23 45
?12 30
small at best
maximal
large
?13 yet to be measured determines
accessibility to CP phase
No good ad hoc model to predict ?13. If ?13 lt
10-3 ?12, perhaps a symmetry?
4
Why Are Neutrino Oscillation Measurements
Important?
Physics at high mass scales, physics of flavor,
and unification Why are neutrino masses so
small? Why are the mixing angles large,
maximal, and small? Is there CP violation, T
violation, or CPT violation in the lepton sector?
Central Questions in Neutrino Oscillation Physics
The Role of ?13
1. What is the ?e coupling of ?3 ? How large is
?13? ?13 an opportunity for discovery
2. What are ?13, ?m231, ?CP, ?12, ?m221, ?23,
?m232? ?13 breaks correlation, helps with
determination of parameters
3. What is the ? mass pattern?
4. Is there CP ? ?13 defines the future of
accelerator ? experiments
5
Reactor Neutrino Measurement of ?13 - Basic Idea
Pee, (4 MeV)
?e flux
?13?
atmospheric frequency dominant last term
negligible for and
6
Concept of a Reactor Neutrino Measurement of ?13
No degeneracies No matter effects
Practically no correlations E? Ee
mn-mp Eprompt Ekin 2me
7
Reactor Neutrino Measurement of ?13
Present Reactor Experiments
Absolute Flux and Spectrum
8
Baseline Optimization for Detector Placement
I. Undistorted vs Distorted Spectrum Optimize FAR
detector with respect to NEAR NEAR - FAR 0.1
km (fixed) 1.7 km
9
Baseline Sensitivity to ?matm2
Detector baselines sensitive to ?matm2.
Need option to adjust baseline once we have
precision measurement ?matm2 . Region of
interest for current ?matm2 region Lfar1.5 -
3 km. Optimize baseline to see oscillation
signature in ratio of spectra.
10
A ?13 Reactor Experiment in the US ?
Site Criteria powerful reactor overburden
(gt 300 mwe) underground tunnels or detector
halls controlled access to site
? Variable/flexible baseline for optimization to
?m2atm and to demonstrate subdominant oscillation
effect ? Optimization of experiment specific to
site. Site selection critical
11
Diablo Canyon - An Ideal Site?
12
Diablo Canyon An Oscillation Experiment with
Variable Baseline?
2 or 3 detectors in 1 km tunnel tunnel
excavation required
13
IIIb
IIIa
Ge
Geology
II
I

• Issues
• folding may have damaged rock matrix
• - steep topography causes landslide risk
• tunnel orientation and key block failure
• seismic hazards and hydrology

14
Tunnel with Multiple Detector Rooms and Movable
Detectors
1-2 km
12 m
Modular, movable detectors Volume scalable
Vfiducial 50-100 t/detector
15
Detector Concept
muon veto
acrylic vessel
5 m
liquid scintillator
buffer oil
1.6 m
passive shield
Movable Detector? Variable baseline to control
systematics and demonstrate oscillation
effect (if ?13 found to be gt 0)
16
Sites in France

• Penly
• In Haute-normandie (north coast)

h115 meters
1.5 km
0.5 km

• Cruas
• In Ardèche (close to the Rhône)

17
Momentum in France
V3
V2
V1
20 tons
Gd
Penly
Cruas

• Muon Veto
• V1 Gd loaded scintillator
• V2 Unloaded scintillator
• V3 Non-scintillating Buffer

_at_?m2atm2.10-3 eV2 sin22?13lt0.025 (90
C.L) 20 t , 3 years
Laboratories involved PCC, Collège de France
CEA/Saclay Activities site evaluations,
phenomenology, Detector simulation
18
Experimental Systematics
Best experiment to date CHOOZ
Ref Apollonio et al., hep-ex/0301017
Reactor Flux near/far ratio, choice of
detector location
Detector Efficiency built near and far detector
of same design calibrate relative
detector efficiency ? variable
baseline may be necessary
Target Volume no fiducial volume cut
Backgrounds external active and passive
shielding for correlated backgrounds
Note list not comprehensive
Total ?syst 1-1.5
19
Past and Present Reactor Neutrino Experiments
20
Future Diablo Canyon Experiment
21
Sensitivity and Complementarity of ?13 Experiments
Sensitivity to sin22?13
Reactor Neutrino Measurement of ?13 No matter
effect Correlations are small, no
degeneracies Insensitive to solar parameters
?12,?m212
Ref Huber et al., hep-ph/0303232
sin22?13 lt 0.01-0.02 _at_ 90 C.L. within reach of
reactor ?13 experiments
10-3
10-2
10-1
22
Future Constraints on ?13
Upper limits correspond to 90 C.L.
23
Parameter Degeneracy
Complementarity of reactor neutrino measurements
of ?13
hep-ph/0211111
observable effect of CP violation scales with ?13
24
Summary Reactor Measurement of ?13
Reactor neutrino oscillation experiment is
promising option to measure ?13. Novel reactor
oscillation experiment gives clean measurement of
sin22?13, no degeneracies, no matter effects. 2
or 3 detectors variable baseline largely
independent of absolute reactor flux and
systematics Sensitivity of sin22?13 0.01
comparable to next-generation accelerator
experiments. Complementary to long-baseline
program. Allows combined analysis of reactor and
superbeam experiments. Negotiations with US
power plants underway. Diablo Canyon is an
attractive possibility.
Moderate Scale (40M) Cost driven by tunnel
excavation Little RD necessary (KamLAND,
SNO, CHOOZ) Construction time 2-3
yrs Start in 2007/2008?
http//theta13.lbl.gov/
25
(No Transcript)