Measuring  13 with Reactors Stuart Freedman HEPAP July 24, 2003 Bethesda Reactor Detector 1Detector 2 d2d2 d1d1

 12 ~ 30°  23 ~ 45°tan 2  13 < 0.03 at 90% CL MNSP Matrix Mass Hierarchy

Minakata and Nunokawa, hep-ph/ Figuring out CP for leptons

? 1/r 2 P ee, (4 MeV) e flux The Basic Idea

First Direct Detection of the Neutrino Reines and Cowan 1956  e+e+ n E  = 2200 keV e E  = 511 keV

Neutrino Spectra from Principal Reactor Isotopes

Inverse Beta Decay Cross Section and Spectrum

from 12 C(n,  )  cap = 188 +/- 23  sec Inverse Beta Decay Signal from KamLAND

1m Poltergeist Chooz 4 m KamLAND 20 m Long Baseline Reactor Neutrino Experiments

CHOOZ

KamLAND

detector 1 Future  13 Reactor Experiment detector 2 Ratio of Spectra Energy (MeV) Two Detector Reactor Experiment Spectral Ratio

Sensitivity to sin 2 2  13 at 90% CL Reactor-I: limit depends on  norm (flux normalization) Reactor-II: limit essentially independent of  norm statistical error only fit to spectral shape  cal relative near/far energy calibration  norm relative near/far flux normalization Reactor I 12 t, 7 GW th, 5 yrs Reactor II 250 t, 7 GW th, 5 yrs Chooz 5 t, 8.4 GW th, 1.5 yrs Ref: Huber et al., hep-ph/

Sensitivity to sin 2 2  13 Ref: Huber et al., hep-ph/ sin 2 2  13 < 90 CL within reach of reactor  13 experiments Knowing  13 is useful for the “intelligent design” of a CP experiments Reactor Neutrino Measurement of  13 No matter effect Correlations are small, no degeneracies Independent of solar parameters  12,  m 21 2 We need accelerators and reactors--Reactors first!

Huber et al hep-ph/

Ref: Marteyamov et al, hep-ex/ Reactor Detector locations constrained by existing infrastructure Features - underground reactor - existing infrastructure ~20000 ev/year ~1.5 x 10 6 ev/year Kr2Det: Reactor  13 Experiment at Krasnoyarsk

L near = 115 m, L far =1000 m, N far = 16000/yr Ratio of Spectra Ref: Marteyamov et al., hep-ex/ Energy (MeV)

Kashiwazaki - 7 nuclear power stations, World’s most powerful reactors - requires construction of underground shaft for detectors near far Kashiwazaki-Kariwa Nuclear Power Station Proposal for Reactor  13 Experiment in Japan

near far 70 m m 6 m shaft, m depth Kashiwazaki: Proposal for Reactor  13 Experiment in Japan

 13 at a US nuclear power plant? Site Requirements powerful reactors overburden controlled access

Berkeley 230 miles Pasadena 200 miles

Powerful: Two reactors ( GW E th ) Overburden: Horizontal tunnel could give 800 mwe shielding Infrastructure: Construction roads. Controlled access. Close to wineries. Diablo Canyon Nuclear Power Plant 1500 ft 2 underground detectors

Detector Concept

~60,000 ~10,000 Statistical error:  stat ~ 0.5% for L = 300t-yr ~250,000 Detector Event Rate/Year Requirements: Overburden and Large Detectors

Neutrino Detectors at Diablo Canyon Possible location Crowbar Canyon Parallel to Diablo Canyon Existing road access Possibility for good overburden Tunnels in radial direction from reactor 2 neutrino detectors, railroad-car size in tunnels at (variable) distance of NEAR/FAR I: km FAR II:1.5-3 km Crowbar Canyon parallel to Diablo Canyon FAR: ~ mwe NEAR: ~ mwe Overburden

MC Studies ‘far-far’ L 1 =6 km L 2 =7.8 km ‘near-far’ L 1 = 1 km L 2 = 3 km Oscillation Parameters: sin 2 2  13 = 0.14  m 2 = 2.5 x eV 2 Optimization

Timescale and Size of a  13 Reactor Project Moderate Scale ( < $50M ) Medium-size, low-energy experiment Little R&D necessary (KamLAND, SNO, CHOOZ) Construction time ~ 2-3 yrs Start in 2007/2008? The Particle Physics Roadmap (in the US)  m 2 23,  23 Reactor  13  13  CP Reactor results will define the future of CP searches in the lepton sector and complement accelerator experiments

Conclusions Top priorities in neutrino physics include pinning down MNS matrix elements and discovering CP violation. We will need a number of experiments to resolve ambiguities from matter effects and correlations. Reactor experiments and accelerator experiments are complementary. Reactor experiments have the potential of being faster, cheaper and better for establishing the value of  13. Executing a reactor experiment at an appropriate site should be put on a fast track.