Future Reactor Neutrino Experiments

1
Future Reactor Neutrino Experiments
Novel Neutrino Oscillation Experiments for
Measuring the Last Undetermined Neutrino Mixing
Angle ?13
Karsten M. Heeger Lawrence Berkeley National
Laboratory
2
Recent Discoveries in Neutrino Physics
Non-accelerator experiments have changed our
understanding of neutrinos
3
UMNSP - Neutrino Mixing Matrix
Present and Future Measurements
Solar
?12 30.3
large
Atmospheric
?23 45
maximal
small at best
Chooz SK
tan2 ?13 lt 0.03 at 90 CL
No good ad hoc model to predict ?13. If ?13 lt
10-3 ?12, perhaps a symmetry?
4
Neutrino Oscillation Parameters
Except for LSND, ?mij2 measured and confirmed.
5
?13 and CP
How large is Ue3?
solar ? present
0??? experiments future
atmospheric ? present
reactor and accelerator ? future
6
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
7
Measuring ?13
Method 1 Accelerator Experiments
appearance experiment measurement of ?? ? ?e
and ?? ? ?e yields ?13,?CP baseline O(100
-1000 km), matter effects present
Method 2 Reactor Neutrino Oscillation
Experiment disappearance experiment
but observation of oscillation signature with 2
or multiple detectors look for deviations from
1/r2 baseline O(1 km), no matter effects
8
Reactor Neutrino Measurement of ?13 - Basic Idea
Pee, (4 MeV)
?e flux
?13?
atmospheric frequency dominant last term
negligible for and
9
Concept of a Reactor Neutrino Measurement of ?13
?e,?,?
?e
O(km)
FAR
NEAR
2-3 detectors, possibly with variable baseline
10
Reactor Neutrino Measurement of ?13
Present Reactor Experiments
Absolute Flux and Spectrum
11
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
12
Baseline Optimization for Detector Placement (II)
Advantages of FAR-FAR Configuration Oscillation
signature in ratio of spectra. Avoid power
plant boundaries at 1km. 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.
13
Kr2Det Reactor ?13 Experiment at Krasnoyarsk
Unique Feature - underground reactor -
existing infrastructure
Detector locations determined by infrastructure
Reactor
Ref Marteyamov et al, hep-ex/0211070
14
Kr2Det Reactor ?13 Experiment at Krasnoyarsk
Energy (MeV)
Ref Marteyamov et al., hep-ex/0211070.
15
Kashiwazaki Proposal for Reactor ?13 Experiment
in Japan
Kashiwazaki - 7 nuclear power stations, Worlds
most powerful reactors - requires
construction of underground shaft for detectors
far
near
near
Kashiwazaki-Kariwa Nuclear Power Station
16
Kashiwazaki Proposal for Reactor ?13 Experiment
in Japan
far
near
near
70 m
70 m
200-300 m
6 m shaft hole, 200-300 m depth
17
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
18
Diablo Canyon - An Ideal Site?
19
Diablo Canyon - An Ideal Site
1500 ft
nuclear reactor
Powerful Two reactors (3.1 3.1 GW Eth) on the
California coast Overburden Horizontal tunnel
could give 800 mwe shielding! Infrastructure
Construction roads. Controlled access.
20
An Ideal Oscillation Experiment with Variable
Baseline? Possible layout of 2 or 3 detectors
at Diablo Canyon
FAR distance 1.5-2.5 km
Diablo Canyon plant boundary
NEAR distance 0.5-1 km
Reactor separation 100 m
Tunnel excavation required
21
An Ideal Oscillation Experiment with Variable
Baseline? Possible layout of 2 or 3 detectors
at Diablo Canyon
FAR distance 1.5-2.5 km
Diablo Canyon plant boundary
NEAR distance 0.5-1 km
Reactor separation 100 m
Tunnel excavation required
22
Neutrino Detectors at Diablo Canyon - NEAR
Space constrained by hills and plant
infrastructure Best overburden to the North
East of power plant
1 km
0.5 km
reactor
23
Neutrino Detectors at Diablo Canyon - FAR
2 neutrino detectors, railroad-car size in
tunnels at (variable) distance of NEAR/FAR I
0.5-1 km FAR II 1.5-3 km
Possible location Crowbar Canyon Parallel to
Diablo Canyon Existing road access Possibility
for good overburden Tunnels in radial direction
from reactor
Crowbar Canyon parallel to Diablo Canyon
24
Movable Detector Concept for Diablo Canyon ?13
Project
liquid scintillator detector active muon
veto Vfiducial 80-100 t
Modular, movable detectors Volume scalable
smaller ?faster larger ? more sensitive
25
Detector and Shielding Concept
Active muon tracker passive
shielding movable, inner liquid scintillator
detector

N S? Bcor Bacc
26
Detector and Shielding Concept
Movable Detector? Variable baseline to control
systematics and demonstrate oscillation
effect (if ?13 found to be gt 0) Non-trivial for
medium-size (100 t), low-background detector

Engineering Study fixed muon veto movable
inner detector
27
Dominant Experimental Systematics
Consider 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
28
Flux Systematics with Multiple Reactor Cores
Neutrino flux at detector I from reactors A and B
Indivual reactor flux contributions and
systematics cancel exactly if Condition I
1/r2 fall-off of reactor flux the same for
all detectors. Condition 2 Survival
probabilities are approximately the same

• Approximate flux cancellation possible at other
  locations

Relative Error Between Detector 1 and
2 rate shape Relative flux error (1) lt
0.6 lt 0.01 Reactor core separation (100 m) lt
0.14 lt 0.1 Finite detector length (10 m) lt
0.2 lt 0.1

• Shape analysis largely insensitive to flux
  systematics.
• Distortions are robust signature of
  oscillations.

Systematic effect due to baseline difference
?baseline ? 0.2
29
Sensitivity to sin22?13 at 90 CL
?cal relative near/far energy calibration
?norm relative near/far flux normalization
Reactor I 12 t, 7 GWth, 5 yrs
Reactor II 250 t, 7 GWth, 5 yrs
Chooz 5 t, 8.4 GWth, 1.5 yrs
fit to spectral shape
Ref Huber et al., hep-ph/0303232
Reactor-I limit depends on ?norm (flux
normalization) Reactor-II limit essentially
independent of ?norm
statistical error only
30
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
31
Past and Present Reactor Neutrino Experiments
32
Future Diablo Canyon Experiment
33
50 Years of Scientific Discoveries at Reactors
1956 Discovery of neutrinos in the US First
detection of reactor neutrinos
1990s Reactor neutrino flux measure-ments in US
and Europe
1995 Nobel Prize to Fred Reines at UC Irvine
2002 Discovery of massive neutrinos and
oscillations
50 years of discoveries
KamLAND, Japan
Next Step Understanding the role of neutrinos in
the early Universe. Why is there matter and not
antimatter?
Diablo Canyon?
34
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.
http//theta13.lbl.gov/