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

€

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

Diablo Canyon - An Ideal Site?

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/

Stokstad, Heeger NSD, May 1, 2003