NEUTRINO OSCILLATION MEASUREMENTS WITH REACTORS R. D. McKeown Caltech NDM09 Madison, Wisconsin Sept. 4, 2009

Outline Reactor antineutrinos – generation, detection KamLAND experiment and results Reactor q13 experiments Conclusions

Neutrino Studies with Nuclear Reactors ne from n-rich fission products detection via inverse beta decay (ne+pge++n) Measure flux and energy spectrum

Discovery of the Neutrino – 1956 F. Reines, Nobel Lecture, 1995 "All you have to do is imagine something that does practically nothing. You can use your son-in-law as a prototype."

Detection Signal n + p g n + e+ g p + e 511keV 2.2 MeV d n Coincidence signal: Prompt: e+ annihilation g En=Eprompt+En+0.8 MeV Delayed: n+p 180 ms capture time, 2.2 MeV n+Gd 30 ms capture time, 8 MeV

The Reactor Neutrino Flux and Spectrum 235U, 239Pu, 241Pu from b measurements 238U calculated Time dependence due to fuel cycle ~ 200 MeV per fission ~ 6 e per fission ~ 2 x 1020 e/GWth-sec Reactor Isotopes

Precise Measurements Flux and Energy Spectrum g ~1-2 % Reactors are calibrated sources of n ’s !!

The Motivation for KamLAND Persistent observations of deficit of solar neutrinos 1998 – observation of oscillations of atmospheric neutrinos by Super-K Unique opportunity to perform longer baseline reactor experiment in Japan

Enter Calibrated source(s) Large detector (1 kton) Long Baseline (180 km) Calibrated source(s) Large detector (1 kton) Deep underground (2700 mwe)

KamLAND uses the entire Japanese nuclear power industry as a Kashiwazaki KamLAND uses the entire Japanese nuclear power industry as a long­baseline source Takahama Ohi Note: The neutrinos are free of charge!

Energy Spectrum

KamLAND Result (2008) Best combined fit values: arXiv:0801.4589v2 [hep-ex] Best combined fit values: Dm2 = 7.59+0.21-0.21 x 10-5 eV2 tan2q = 0.47+0.06-0.05

Maki – Nakagawa – Sakata Matrix Gateway to CP Violation! CP violation

CHOOZ/Palo Verde limits for 13 Allowed region At m231 = 2.5  103 eV2, sin22 < 0.15

Hints from Global Fits → sin22q13 ~ 0.06-0.08? Fogli, et al., arXiv:0905:3549 Also: A. B. Balantekin and D. Yilmaz, J. Phys. G 35, 075007 (2008) → sin22q13 ~ 0.06-0.08?

Theoretical Predictions for q13

ne Survival Probability Dominant 12 Oscillation near far Subdominant 13 Oscillation “Clean” measurements of q, Dm2 No CP violation Negligible matter effects

Reactor θ13 Neutrino Experiments Chooz, France RENO, Korea Daya Bay, China Angra, Brazil Under construction. Proposed and R&D.

1051 m 380 m Two identical detectors:10 tons each. Phase 1 (2010): Far Detector in existing lab. Phase 2 (2011-12): running with Near detector in new lab. 1051 m 380 m Status(July09): PMT’s installed at far site Acrylic vessels constructed Veto under construction

Near Detector Tunnel Length 100 m 70 m Hill Tunnel Length 300 m 1.4 km Far Detector Near Detector Tunnel Length 300 m Tunnel Length 100 m 1.4 km 200 m Mt. 70 m Hill http://www.awa.tohoku.ac.jp/taup2007/slides/workshop14/roomA/05-RENO-TAUP07.ppt

Comparison Table Experiment Thermal Power (GW) Distances Near/Far (m) Depth (mwe) Target Mass (tons) Start Date Sensitivity @2.5x10-3 eV2 90% CL, 3 years Double-CHOOZ (France) 8.6 410/1050 115/300 8.8/8.8 4/2010, 2011 0.032 RENO (So. Korea) 17.3 290/1380 120/450 15/15 2010? 0.02 Daya Bay (China) 17.4 363(481) / 1985(1613) 260/910 40(2) / 80 2011 0.008

Daya Bay Nuclear Power Plant 4 reactor cores, 11.6 GW 2 more cores in 2011, 5.8 GW Mountains provide overburden to shield cosmic-ray backgrounds Baseline ~2km Multiple detectors → measure ratio

Experiment Layout Multiple detectors 20T per site cross-check detector efficiency Two near sites sample flux from reactor groups 20T Total Tunnel length ~ 3000 m

Antineutrino Detector SS Tank Acrylic Vessels 20 T Gd-doped liquid scintillator Calibration units Gamma catcher Buffer oil 192 8” PMT’s 3 zone design Uniform response No position cut 12%/√ E resolution

Muon Veto System RPC’s Water Cerenkov (2 layers) Redundant veto system → 99.5% efficient muon rejection

Site Preparation Assembly Building Tunnel lining Daya Bay Near Hall construction (100m underground) Assembly Building Tunnel lining Portal of Tunnel

Civil Construction Status Far Hall Ling Ao Hall Tunnel Entrance Daya Bay Near Hall Construction Tunnel

Hardware Progress Transporter SSV Prototype 4m Acrylic Vessel Prototype Transporter Calibration Units

Detector Assembly Delivery of 4m AV SS Tank delivery Clean Room

Transporting the Prototype Detector

Sensitivity to Sin22q13 Experiment construction: 2008-2011 Start acquiring data: 2011 3 years running

Project Schedule October 2007: Ground breaking August 2008: CD3 review (DOE start of construction) March 2009: Surface Assembly Building occupancy Summer 2009: Daya Bay Near Hall occupancy Fall 2009: First AD complete Summer 2010: Daya Bay Near Hall ready for data Summer 2011: Far Hall ready for data (3 years of data taking to reach goal sensitivity)

Sensitivity of q13 Experiments Huber et al., 0907.1896

Conclusions Reactor neutrino experiments have entered “precision era” KamLAND provided the first “laboratory” evidence for neutrino oscillations, with a high precision measurement of Dm122 RENO, Double-CHOOZ, Daya Bay will study q13 during 2010-14, with Daya Bay reaching sin22q13<0.01 If reactor experiments establish θ13 to be sufficiently large, Nova may then contribute unique sensitivity to the mass hierarchy in the next decade. In addition, the value of θ13 will provide necessary guidance to future accelerator-based long baseline experiments.

Stay Tuned !!