Measuring sin 2 2 θ 13 with Reactor Antineutrinos - Proposals with US Involvement - Karsten Heeger Lawrence Berkeley National Laboratory Karsten Heeger US-Japan Seminar, September 17, 2005
Understanding Neutrino Mixing Atmospheric Solar Reactor (Super-K) (SNO) (KamLAND) CHOOZ � U e 1 U e 2 U e 3 � U MNSP Matrix � � U = U µ 1 U µ 2 U µ 3 � � hep-ph/0405172 � � U � 1 U � 2 U � 3 � � e � i � CP sin � 13 � � � 1 0 0 � cos � 13 0 � cos � 12 sin � 12 0 � � 1 0 0 � � � � � � � � � e i � / 2 0 cos � 23 sin � 23 0 1 0 � sin � 12 cos � 12 0 0 0 = � ? � � � � � � � � � � � � � � � � � � � e i � CP sin � 13 e i � / 2 + i � 0 � sin � 23 cos � 23 0 cos � 13 0 0 1 0 0 � � � � � � � � atmospheric, K2K reactor and accelerator SNO, solar SK, KamLAND 0 νββ θ 13 = ? θ 23 = ~ 45° θ 12 ~ 32° Karsten Heeger US-Japan Seminar, September 17, 2005
θ 13 from Reactor and Accelerator Experiments reactor � � � � 2 L 2 L ee � 1 � sin 2 2 � 13 sin 2 � m 31 � � cos 4 � 13 sin 2 2 � 12 sin 2 � m 21 P � � � 4 E � 4 E � � � � � - Clean measurement of θ 13 - No matter effects mass hierarchy CP violation accelerator matter - sin 2 2 θ 13 is missing key parameter for any measurement of δ CP Karsten Heeger US-Japan Seminar, September 17, 2005
A Precision Measurement of θ 13 Next-generation experiments will not measure CP violation but some values of δ CP could be excluded. hep-ex/0409028 Karsten Heeger US-Japan Seminar, September 17, 2005
Measuring θ 13 with Reactor Antineutrinos Precision Oscillation Measurement as a Function of Distance from Source � 2 L � � 2 L � ee � 1 � sin 2 2 � 13 sin 2 � m 31 � � cos 4 � 13 sin 2 2 � 12 sin 2 � m 21 P � � � 4 E � 4 E � � � � � θ 13 Relative ν e flux measurement at different distances. Diablo Canyon ν e ν e ν e 0.5-2 km nuclear reactor Event rate: ~1 event/GW/ton/day at 1km underground scintillator ν detectors, ~40-200t Projected sensitivity: sin 2 2 θ 13 ≈ 0.01 Karsten Heeger US-Japan Seminar, September 17, 2005
Signatures of θ 13 in a Reactor Experiment Disappearance of ν e : Reduction of interaction rate near far comparison Rate and shape effects optimize at different baselines ratio mid/far 1 km Spectral Distortion P ee mid far comparison 2.5 km → 3 baselines provide consistency checks and eliminate single point failure of experiment, in particular if the backgrounds are too high in near detector or unaccounted systematics in one Karsten Heeger US-Japan Seminar, September 17, 2005 of detectors
Proposals to Measure θ 13 with Reactor Neutrinos Krasnoyarsk, Russia Diablo Canyon, CA Braidwood, Il Kashiwazaki, Japan Daya Bay, China Chooz, France horizontal tunnels vertical shafts Karsten Heeger US-Japan Seminar, September 17, 2005
Proposals to Measure θ 13 with Reactor Neutrinos Krasnoyarsk, Russia Diablo Canyon, CA Braidwood, Il Braidwood Double Chooz Daya Bay Kashiwazaki, Japan Daya Bay, China Chooz, France horizontal tunnels vertical shafts Karsten Heeger US-Japan Seminar, September 17, 2005
DoubleChooz …Improving on Chooz ‘ Double-Chooz ’ Project 10 tons detectors 8.4 GW th reactor power 300 mwe overburden at far site ~50 mwe overburden at near site 0.1-0.2 km 1.05 km Sensitivity sin 2 (2 θ 13 ) < 0.03 at 90% CL 2 = 2 x 10 -3 eV 2 after 3 yrs, Δ m atm → Improve the detector concept → and backgrounds rejection on Chooz Karsten Heeger US-Japan Seminar, September 17, 2005
Prototype Development 1/5 scale acrylic vessel buffer to reduce backgrounds Liquid scintillator + Gd Liquid scintillator (gamma catcher) 3-zone detector Karsten Heeger US-Japan Seminar, September 17, 2005
Double Chooz Sensitivity (2007-2012) Far & Near detectors Far detector Far detector starts in 2007 together only σ sys =0.6% σ sys =2.5% σ sys =2.5% Near detector 16 months later Δ m 2 atm = 2.8 10 -3 eV 2 Will be known to 20% by MINOS Far detector starts Near detector starts 2004 2005 2006 2008 2009 2007 2003 Site Proposal & design Construction ? Data taking Karsten Heeger US-Japan Seminar, September 17, 2005
Braidwood Neutrino Experiment Braidwood Setup • Two 3.6 GW reactors • near: 2x65 ton (fid vol), 270 m • far : 2x65 ton (fid vol), 1510 m • 180m shafts and detector halls (450 mwe) depth • optimized distances Braidwood Karsten Heeger US-Japan Seminar, September 17, 2005
Braidwood Detector Concept • Transport for moving detectors from construction/filling area to underground halls. • Moving required for cross checks. • Outer steel buffer oil containment (7m diameter) • Inner acrylic Gd-Scint containment (5.2m diameter) • 2-zone detector • 1000 low activity glass 8” PMTs (25% coverage) Goal: < 1 neutron background event/day/detector Karsten Heeger US-Japan Seminar, September 17, 2005
Braidwood Sensitivity and Discovery Potential 3 years, Δ m 2 > 2.5 x 10 -3 eV 2 90% CL limit at sin 2 2 θ 13 < 0.005 3 σ discovery for sin 2 2 θ 13 > 0.013 Uncertainties for 3 yr Data Karsten Heeger US-Japan Seminar, September 17, 2005
Daya Bay Nuclear Power Plant Powerful ν e Source: Multiple reactor cores. (4 units 11.6 GW E th, eventually 6 units 17.4 GW E th ) Shielding from Cosmic Rays: Up to 1200 mwe overburden nearby. Infrastructure: Construction roads. Controlled access. Karsten Heeger US-Japan Seminar, September 17, 2005
Daya Bay Nuclear Power Plant Laboratory with Horizontal Tunnels - Simplifying logistics: Build detectors outside before moving into tunnel. - Swapping detectors: Eliminates most systematic errors. Helps understand backgrounds. - Modular detectors: Phased approach, 30-40t allowing rapid deployment, different target mass configurations, and cross-calibration. -Optimizing distance to reactors Karsten Heeger US-Japan Seminar, September 17, 2005
Tunnel Layout at Daya Bay ~0% slope 2x 2.9 GW th Ling Ao ll ~0% slope (under construction) 2x 2.9 GW th ~0% slope Ling Ao 670 m, ~12% slope only for extraction of waste rock access portal 8% slope • Maximize overburden 2x 2.9 GW th • Optimize distances to reactors: Daya Bay - maximize sensitivity - cancel reactor systematics Karsten Heeger US-Japan Seminar, September 17, 2005 • Flexible configuration
Tunnel Layout at Daya Bay FAR SITE overburden ~1050 mwe distance to Daya Bay ~1900 m distance to Ling Ao ~1600 m Ling Ao NEAR SITE overburden ~300 mwe distance to Ling Ao ~500 m distance to Daya Bay ~1300 m Ling Ao ll (under construction) MID SITE overburden ~620 mwe distance to Daya Bay ~1100 m distance to Ling Ao ~750 m Ling Ao access portal Daya Bay NEAR SITE Site Reactor ν e Signal (/day ) overburden ~300 mwe near 1160 distance to Daya Bay ~360 m distance to Ling Ao ~900 m mid 464 Daya Bay far 116 Not a rare event experiment, Karsten Heeger US-Japan Seminar, September 17, 2005 precision oscillation physics.
Development of Multi-Layer Detector Modules Option A: horizontal, cylindrical modules ~600 externally mounted PMTs ~40cm of mineral 12% PMT coverage oil buffer to � E 7% E ~ reduce E ( MeV ) backgrounds Liquid scintillator + Gd Liquid scintillator (gamma catcher) ν e +p → e + +n → evaluating need for 2 or 3 zones Electronics ~40 ton fiducial volume integrated calibration systems • movable over a distance of ~2km Karsten Heeger US-Japan Seminar, September 17, 2005
Detector Design Studies Option B: vertical, upright modules - multiple modules, easier to fabricate - modular muon shielding with water tanks Roof shown slide back to reveal detector modules. Karsten Heeger US-Japan Seminar, September 17, 2005
Technical Challenges: Multi-Layer Acrylic Detectors A commercial double-walled acrylic tank Evaluating need for 2 or 3 zones: • third layer increases cost, difficulty of construction, complexity stress analysis threshold on positron spectrum? gamma cascade tail? 2-zone: cascade cut at ~4MeV gives an uncertainty of <0.2% for threshold uncertainties <1% Karsten Heeger US-Japan Seminar, September 17, 2005
Movable Detector Modules in Underground Halls Swapping: Cancellation of systematics Side-by-Side Calibration : Initial side-by-side calibration at near site Cross-Check of Modules Karsten Heeger US-Japan Seminar, September 17, 2005
Mountainous Site With Horizontal Access Tunnel 707 m • reduce systematics by swapping • access to large overburden • Daya Bay offers up to 1100 mwe overburden Muon flux underground Antineutrino candidate signal: Correlated Backgrounds ν e +p → e + +n - Muon spallation - 9 Li - Fast neutrons Karsten Heeger US-Japan Seminar, September 17, 2005
Correlated Backgrounds Measuring 9 Li Muon flux low enough at mid and far sites so that we can measure 9 Li production and subtract it. mid: depth 560 mwe 0.176/m 2 /sec µ 9 Li 0.32 ± 0.10% far: depth ~1100 mwe 0.016/m 2 /sec µ 9 Li 0.17 ± 0.14% → 9 Li at KamLAND, D. Dwyer, JG10 near: muon flux high, we cannot make sufficiently precise measurement of 9 Li background, need calculation based on measurements at mid and far site Ref: Daya Bay US LOI Karsten Heeger US-Japan Seminar, September 17, 2005
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