Karsten Heeger, LBNL INPAC, October 3, 2003 Reactor Neutrino Oscillation Experiments Karsten M. Heeger Lawrence Berkeley National Laboratory

Karsten Heeger, LBNL INPAC, October 3, 2003 Recent Discoveries in Neutrino Physics Non-accelerator experiments have changed our understanding of neutrinos Atmospheric+Solar (Super-K) Solar (SNO) Reactor (KamLAND) Neutrinos are not massless (mass is small: m e < m e ) Evidence for neutrino flavor conversion e   Combination of experimental results show that neutrinos oscillate

Karsten Heeger, LBNL INPAC, October 3, 2003 Solar Neutrinos in the Big Picture Reactor and Beamstop Neutrinos   s  e Atmospheric and Reactor Neutrinos    Solar and Reactor Neutrinos e  ,  Before 2002 Status: Summer 2002 Large mixing favored LMA solution can be tested with reactor neutrinos ? Murayama

Karsten Heeger, LBNL INPAC, October 3, 2003 Search for Neutrino Oscillations with Reactor Neutrinos 50 Years of Reactor Neutrino Physics 1953 First reactor neutrino experiment 1956 “Detection of Free Antineutrino”, F. Reines and C.L. Cowan  Nobel Prize in 1995 No signature of neutrino oscillations until 2002! Japan Results from solar experiments suggest study of reactor neutrinos with a baseline of ~ 180 km

Karsten Heeger, LBNL INPAC, October 3, 2003 KamLAND - Kamioka Liquid Scintillator Antineutrino Detector "Dome" Area Outer Detector Water Cherenkov Steel Deck Steel Sphere Tyvek light baffles OD PMT's Nylon Balloon Uses reactor neutrinos to study oscillation with a baseline of L ~ km Coincidence Signal: e + p  e + + n Prompt e + annihilation Delayed n capture, ~ 210  s capture time Coincidence Signal: e + p  e + + n Prompt e + annihilation Delayed n capture, ~ 210  s capture time (a) Flux at detector (b) cross-section (c) Interactions in detector KamLAND studies the disappearance of e and measures interaction rate energy spectrum (a) (b) (c) Energy (MeV)

Karsten Heeger, LBNL INPAC, October 3, 2003 First Evidence for e Disappearance at KamLAND LMA parameters from: G.Fogli et al., PRD 66, , (2002) LMA:  m 2 = 5.5x10 -5 eV 2 sin 2 2  = 0.833

Karsten Heeger, LBNL INPAC, October 3, 2003 KamLAND Neutrino Program 180 km Phase I: Reactor and Geo Neutrinos oscillation search Terrestrial detection Phase II: Solar Neutrinos Direct detection of 7 Be Solar e search, supernova detection, Nucleon decay

Karsten Heeger, LBNL INPAC, October 3, 2003 Neutrino Oscillation Parameters Beamstop Neutrinos   s  e Atmospheric, Reactor, Accelerator Neutrinos    Solar and Reactor Neutrinos e  ,  Except for LSND,  m ij 2 measured and confirmed.

Karsten Heeger, LBNL INPAC, October 3, 2003  13 and CP Violation atmospheric, K2K U MNSP Neutrino Mixing Matrix Dirac phase Majorana phases reactor and accelerator 0  SNO, solar SK, KamLAND  12 ~ 30°  23 = ~ 45° tan 2  13 < 0.03 at 90% CL maximal large small … at best No good ‘ad hoc’ model to predict  13. If  13 <  12, perhaps a symmetry? ?  13 yet to be measured determines accessibility to CP phase

Karsten Heeger, LBNL INPAC, October 3, 2003 Why Are Neutrino Oscillation Measurements Important? Central Questions in Neutrino Oscillation Physics & The Role of  What is the e coupling of 3 ? How large is  13 ?  13 : an opportunity for discovery 2. What are  13,  m 2 31,  CP,  12,  m 2 21,  23,  m 2 32 ?  13 : breaks correlation, helps with determination of parameters 4. Is there CP ?  13 : defines the future of accelerator experiments Time 3. What is the mass pattern? Physics at high mass scales, physics of flavor, and unification: Why are neutrino masses so small? Why are the mixing angles large, maximal, and small? Is there CP violation, T violation, or CPT violation in the lepton sector?  13 The Mystery of the Matter-Antimatter Asymmetry Understanding the role of neutrinos in the early Universe ? Is there a connection between the lepton and the baryon sector?

Karsten Heeger, LBNL INPAC, October 3, 2003 S. GlashowL. Wofenstein B. Kayser A. Smirnov S. Bilenky

Karsten Heeger, LBNL INPAC, October 3, 2003  13 =? Reactor Neutrino Measurement of  13 - Basic Idea atmospheric frequency dominant last term negligible for and 1/r 2 P ee, (4 MeV) e flux

Karsten Heeger, LBNL INPAC, October 3, 2003 Concept of a Reactor Neutrino Measurement of  13 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

Karsten Heeger, LBNL INPAC, October 3, 2003 Reactor Neutrino Measurement of  13 Present Reactor Experiments (a) (b) (c) Energy (MeV) (a) Flux at detector (b) cross-section (c) spectrum in detector detector 1 Future  13 Reactor Experiment detector 2 Ratio of Spectra Energy (MeV) independent of absolute reactor flux eliminate cross-section errors relative detector calibration rate and shape information Absolute Flux and Spectrum

Karsten Heeger, LBNL INPAC, October 3, 2003 Diablo Canyon - An Ideal Site? 1500 ft nuclear reactor 2 underground detectors Powerful (two reactors GW E th ) Overburden (up to 700 mwe) Infrastructure (roads, controlled access)

Karsten Heeger, LBNL INPAC, October 3, 2003 Tunnel with Multiple Detector Rooms and Movable Detectors 5 m ~12 m Modular, movable detectors Volume scalable V fiducial ~ t/detector km

Karsten Heeger, LBNL INPAC, October 3, 2003 liquid scintillator buffer oil muon veto passive shield Detector Concept 5 m 1.6 m Movable Detector? Variable baseline to control systematics and demonstrate oscillation effect (if |  13 | > 0) acrylic vessel

Karsten Heeger, LBNL INPAC, October 3, 2003 Past and Present Reactor Neutrino Experiments

Karsten Heeger, LBNL INPAC, October 3, 2003 Future Diablo Canyon Experiment

Karsten Heeger, LBNL INPAC, October 3, 2003 Future 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.

Karsten Heeger, LBNL INPAC, October 3, 2003 Diablo Canyon - An Initiative in California Science -Neutrino particle physics -Reactor monitoring -Geological studies -Low-background counting … and Outreach

Karsten Heeger, LBNL INPAC, October 3, First observation of neutrinos 1980s & 1990s Reactor neutrino flux measurements in U.S. and Europe 2002 Discovery of massive neutrinos and oscillations 2003 and beyond Understanding the role of neutrinos in the universe Past Experiments Hanford Savannah River ILL, France Bugey, France Rovno, Russia Goesgen, Switzerland Krasnoyark, Russia Palo Verde Chooz, France Reactors in Japan 1995 Nobel Prize to Fred Reines at UC Irvine 50 Years of Scientific Discoveries at Reactors

Karsten Heeger, LBNL INPAC, October 3, 2003 Measuring  13 with Reactors: Summary Reactor neutrino oscillation experiment is promising option to measure  13. Novel reactor oscillation experiment gives clean measurement of sin 2 2  13, no degeneracies, no matter effects. 2 or 3 detectors, variable baseline largely independent of absolute reactor flux and systematics Diablo Canyon offers possibility for geol. studies and low-backg. counting. Sensitivity of sin 2 2  13 ~ 0.01 comparable to next-generation accelerator experiments. Complementary to long-baseline program. Allows combined analysis of reactor and superbeam experiments. Negotiations with PG&E and the Diablo Canyon power plant are underway. Moderate Scale (~$40M) Cost driven by tunnel excavation Little R&D necessary (KamLAND, SNO, CHOOZ) Construction time ~ 2-3 yrs Start in 2007/2008?

Karsten Heeger, LBNL INPAC, October 3, 2003