Measuring  13 with Reactors Stuart Freedman University of California at Berkeley SLAC Seminar September 29, 2003

I am going to argue that -- the fastest and cheapest way to determine the value of Sin 2 2  13 is to measure two big things and subtract the results. - = How to Weigh Dumbo’s Magic Feather  13

Neutrino LANDscape

Constraints from most recent Experiments

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

Slide Courtesy of B. Kayser What do we know and how do we know it

Is it important to measure  13 ?

Testimonials L. Wofenstein S. Glashow B. KayserS. Bilenky A Smirnov

Measuring  13 Accelerator Experiments appearance experiment measurement of   e and   e yields  13,  CP baseline O( 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/r 2 baseline O(1 km), no matter effects e e e decay pipe horn absorber target p detector ++ ++ ++

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

Basic Idea for a Disappearance Experiment ?

Reactor Detector 1Detector 2 d2d2 d1d1 Experimental Design

First Direct Detection of the Neutrino Reines and Cowan 1956  e n e+e+ 2.2MeV Scintillator

Inverse Beta Decay Cross Section and Spectrum

Neutrino Spectra from Principal Reactor Isotopes 235 U fission

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

CHOOZ

KamLAND

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

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

Diablo Canyon Power Station

No degeneracies No matter effects Practically no correlations E = E e + m n -m p E prompt = E kin + 2m e scintillator e detectors e + p  e + + n coincidence signal prompt e + annihilation delayed n capture (in  s) disappearance experiment look for rate deviations from 1/r 2 and spectral distortions observation of oscillation signature with 2 or multiple detectors baseline O(1 km), no matter effects e < 1 km e, ,  ~ km

Overburden Essential for Reducing Cosmic Ray Backgrounds

~60,000 ~10,000 Statistical error:  stat ~ 0.5% for L = 300t-yr ~250,000 Detector Event Rate/Year Statistical Precision Dominated by the Far Detector

2 or 3 detectors in km tunnel Diablo Canyon Variable Baseline

Ge Issues - folding may have damaged rock matrix - steep topography causes landslide risk - tunnel orientation and key block failure - seismic hazards and hydrology Geology I II IIIa IIIb

liquid scintillator buffer oil muon veto passive shield Detector Concept 5 m 1.6 m Variable baseline to control systematics and demonstrate oscillations (if |  13 | > 0) acrylic vessel

Movable Detectors 5 m ~12 m Modular, movable detectors Volume scalable V fiducial ~ t/detector km

Kashiwazaki:  13 Experiment in Japan - 7 nuclear reactors, World’s largest power station near far Kashiwazaki-Kariwa Nuclear Power Station

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

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

% 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 % Systematic Uncertainties E > 2.6 MeV

Systematics Reactor Flux near/far ratio, choice of detector location Best experiment to date: CHOOZ Target Volume & well defined fiducial volume Backgrounds external active and passive shielding for correlated backgrounds Detector Efficiency built near and far detector of same design calibrate relative detector efficiency  variable baseline may be necessary Ref: Apollonio et al., hep-ex/ Total  syst ~ 1-1.5%  rel eff ≤ 1%  target ~ 0.3%  n bkgd < 1%  flux < 0.2%  acc < 0.5%.

MC Studies Normalization: 10k events at 10km ‘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 at LBNL

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/

statistics Statistics Systematics Correlations Degeneracies Ref: Huber et al., hep-ph/

Expected Constraints on  13 Experiment sin 2 (2  13 )  13 When? CHOOZ< 0.11< 10 NUMI Off- Axis (5 yr)< < JPARC-nu (5 yr)< < MINOS< 0.06< ICARUS (5 yr)< 0.04< OPERA (5 yr)< 0.06< KR2DET (Russia)< 0.016< 3.6? Kashiwazaki (Japan)< 0.026< 4.6[2008] Penly/Cruas (France)< 0.025< 4.5[2010] Diablo Canyon (US)< < 2.9[2009] Upper limits correspond to 90% C.L.