Stokstad, Heeger NSD, May 1, 2003
Reactor Neutrino Measurement of 13
Measuring the Last Undetermined Neutrino Mixing Angle 13
Searching for Subdominant Oscillations in e ,
Stokstad, Heeger NSD, May 1, 2003
13 and CP Violation
?
Neutrino Mixing Matrix
13 is key parameter for oscillation phenomenology since 12 and 23 are both large
13 determines whether CP violation is accessible
CP proportional to 13
13 is key parameter for oscillation phenomenology since 12 and 23 are both large
13 determines whether CP violation is accessible
CP proportional to 13
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U =
Ue1 Ue2 Ue3
Uμ1 Uμ 2 U μ 3
Uτ1 Uτ 2 Uτ 3
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
=
cosθ12 sinθ12 0
−sinθ12 cosθ12 0
0 0 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟×
cosθ13 0 e−iδ CP sinθ13
0 1 0
−e iδCP sinθ13 0 cosθ13
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟×
1 0 0
0 cosθ23 sinθ23
0 −sinθ23 cosθ23
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟×
1 0 0
0 e iα / 2 0
0 0 e iα / 2+iβ
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
atmospheric present
solar present
reactor and accelerator future
0 experimentsfuture
Stokstad, Heeger NSD, May 1, 2003
Reactor Neutrino Measurement of 13
Detector 1
Detector 2
Searching for Subdominant Oscillations in e ,
to measure the last yet undetermined
neutrino mixing angle, 13
P νe → νe( )≈sin4θ13+cos4θ13 1−sin2(2θ12) ⋅sin2 Δm122 L
4Eν
⎛
⎝ ⎜
⎞
⎠ ⎟
⎧ ⎨ ⎩
⎫ ⎬ ⎭
13 oscillation signature
Stokstad, Heeger NSD, May 1, 2003
Sensitivity and Complementarity of 13 Experiments
Reactor 13 experiment
No matter effect
Correlations are small, no degeneracies
Independent of solar osc. parameters 12,m212
sin2213 sensitivity limit
m213 dependence
Tru
e va
lue
of
m2
31
(eV
2)
Sensitivity to sin2213
10-110-3 10-2
Ref: Huber et al., hep-ph/0303232
13 sensitivity of reactor experiments comparable to JHF-SK
Stokstad, Heeger NSD, May 1, 2003
Movable detectors?
Does a site like this exist?
Site Requirements
1. A reactor, or multiple-reactor complex
2. Sites for 2-3 detectors at distances of 1-5 km from reactor
3. Detector overburden for reduction of cosmic ray background• Man-made overburden or• Underground site in a mine (good overburden)• Underground site in tunnels (movable detectors)
A 13 Reactor Experiment in the US ?
Stokstad, Heeger NSD, May 1, 2003
• Powerful: Two reactors (3.1+3.1 GW Eth) on the California coast• Overburden: Horizontal tunnel could give 800 mwe shielding!• Infrastructure: Roads built for heavy machinery. Controlled access. • Scientific Collaborations: existing collaborations between PG&E and marine scientists, biologists, and geologists with site access.
Diablo Canyon Site
1500 ft
600 ft
Stokstad, Heeger NSD, May 1, 2003
~ 600-800 mwe
FAR II: distance 2-2.5 km
FAR I: distance 1.5-2 km
NEAR: distance~ 0.5 km
Tunnel excavation required
further studies necessary
An Ideal Oscillation Experiment with Variable Baseline?
Possible layout of 2 or 3 detectors at Diablo Canyontunnels
~ 400 mwe
Stokstad, Heeger NSD, May 1, 2003
Schematic of Movable Detector
• Modular, movable liquid scintillator detector to control systematics• active muon veto• Vfiducial ~ 80-100 t
Stokstad, Heeger NSD, May 1, 2003
Summary: Reactor Measurement of 13
• Measurement of fundamental neutrino mixing angle with discovery opportunity and long-term impact.
• Reactor experiment gives clean measurement of sin2213.
• Sensitivity of sin2213 < 0.005 comparable to next-generation accelerator experiments.
• A timely 13 measurement will define the future of accelerator physics.
• Reactor results will be on a timescale that complements off-axis results
• Further design studies and site evaluation necessary.
http://theta13.lbl.gov/