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Measuring q 13 with Reactors Stuart Freedman University of California at Berkeley SLAC Seminar September 29, 2003. q 13. How to Weigh Dumbo’s Magic Feather. I am going to argue that 
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Measuring q13 with Reactors
Stuart Freedman
University of California at Berkeley
SLAC Seminar September 29, 2003
q13
How to Weigh Dumbo’s Magic Feather
I am going to argue that 
the fastest and cheapest way to determine the value of Sin22q13 is to measure two big things and subtract the results.

=
Neutrino LANDscape
Constraints from most recent Experiments
UMNSP Matrix
12 ~ 30°
tan2 13 < 0.03 at 90% CL
23 ~ 45°
Mass Hierarchy
What do we know and how do we know it
Slide Courtesy of B. Kayser
Is it important to measure q13?
L. Wofenstein
B. Kayser
S. Bilenky
S. Glashow
A Smirnov
Testimonials
absorber
decay pipe
detector
p
target
horn
+
+
+
e
e
e
Accelerator Experiments
• appearance experiment
• measurement of e and e yields 13,CP
• baseline O(100 1000 km), matter effects present
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
Figuring out CP for leptons
Minakata and Nunokawa, hepph/0108085
Basic Idea for a Disappearance Experiment
?
d2
d1
Detector 2
Detector 1
Reactor
Experimental Design
First Direct Detection of the Neutrino
Scintillator
ne
e+
n
2.2MeV
n
m
Reines and Cowan 1956
Inverse Beta Decay Cross Section and Spectrum
235U fission
Neutrino Spectra from Principal Reactor Isotopes
20 m
KamLAND
4 m
Chooz
1m
Long Baseline Reactor Neutrino Experiments
Poltergeist
CHOOZ
CHOOZ
KamLAND
KamLAND
Inverse Beta Decay Signal from KamLAND
from 12C(n, g )
tcap = 188 +/ 23 msec
q13 at a US nuclear power plant?
Site Requirements
• powerful reactors
• overburden
• controlled access
Diablo Canyon Power Station
scintillator e detectors
e + p e+ + n
coincidence signal
prompt e+ annihilation
delayed n capture (in s)
e,,
~ 1.52.5km
e
< 1 km
• disappearance experiment
• look for rate deviations from 1/r2 and spectral distortions
• observation of oscillation signature with 2 or multiple detectors
• baseline O(1 km), no matter effects
Overburden Essential for Reducing Cosmic Ray Backgrounds
Detector Event Rate/Year
~250,000
~60,000
~10,000
Statistical error: stat ~ 0.5%for L = 300tyr
Statistical Precision Dominated by the Far Detector
Diablo Canyon
Variable Baseline
2 or 3 detectors in 11.5 km tunnel
IIIb
IIIa
Ge
Geology
II
I
muon veto
acrylic vessel
5 m
liquid scintillator
buffer oil
1.6 m
passive shield
Variable baseline to control systematics and demonstrate oscillations (if 13 > 0)
6
10
5 m
Movable Detectors
12 km
~12 m
• Modular, movable detectors
• Volume scalable
• Vfiducial ~ 50100 t/detector
 7 nuclear reactors, World’s largest power station
far
near
near
KashiwazakiKariwa
Nuclear Power Station
far
near
near
70 m
70 m
200300 m
6 m shaft hole, 200300 m depth
~20000 ev/year
~1.5 x 106 ev/year
Features
 underground reactor
 existing infrastructure
Detector locations constrained by existing infrastructure
Reactor
Ref: Marteyamov et al, hepex/0211070
Systematic Uncertainties
%
Total LS mass2.1
Fiducial mass ratio4.1
Energy threshold2.1
Tagging efficiency2.1
Live time0.07
Reactor power2.0
Fuel composition1.0
Time lag0.28
e spectra2.5
Cross section0.2
Total uncertainty6.4 %
E > 2.6 MeV
.
flux < 0.2%
rel eff ≤ 1%
target ~ 0.3%
acc < 0.5%
nbkgd< 1%
Best experiment to date: CHOOZ
Ref: Apollonio et al., hepex/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 &• well defined fiducial volume
Backgrounds • external active and passive shielding for correlated backgrounds
Total syst ~ 11.5%
Optimization at
LBNL
‘nearfar’ L1 = 1 km
L2 = 3 km
‘farfar’ L1=6 km
L2=7.8 km
Normalization:
10k events at 10km
Oscillation Parameters:
sin2213 = 0.14
m2= 2.5 x 103 eV2
Sensitivity to sin2213at 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
Chooz5 t, 8.4 GWth, 1.5 yrs
fit to spectral shape
Ref: Huber et al., hepph/0303232
ReactorI: limit depends on norm (flux normalization)
ReactorII: limit essentially independent of norm
statistical error only
Ref: Huber et al., hepph/0303232
statistics
Statistics
Systematics
Correlations
Degeneracies
Upper limits correspond to 90% C.L.