CaoJun ICFP2005

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Daya Bay Neutrino Experiment: 

Jun Cao Institute of High Energy Physics, Beijing Daya Bay Neutrino Experiment 3rd International Conference on Flavor Physics, Oct. 3-8, 2005 National Central University Chung-li, Taiwan

Neutrino Oscillation: 

Neutrino Oscillation Neutrino Mixing: PMNS Matrix Known: |Dm232|, sin22q23, Dm221, sin22q12 Unkown: sin22q13, dCP, Sign of Dm232

Reactor Neutrino: 

Reactor Neutrino

Physics Goal: 

Physics Goal The proposed Daya Bay Experiment will measure sin2213 to 0.01 or better at 90% C.L. in a three-year run (2001). And a direct measurement of m231 Beta beam  1e-4 ? Reactor Neutrino: Fast, Cheap, and Clean! Mature technique, Chooz, Palo Verde, KamLAND but challenging on controlling systematics.

Location of Daya Bay: 

Location of Daya Bay Two metropolises Hong Kong 55 km 12 maximum ShenZhen 45 km

The Site: 

The Site Daya Bay NPP 2.9GW2 LingAo NPP 2.9GW2 LingAo II NPP 2.9GW2 Under construction (2010)

Tunnel Layout: 

Tunnel Layout Horizontal tunnel Approved by Power Plant Total Tunnel length ~ 3200 m Detector swapping cancels most detector systematic error. Residual error ~ 0.2% Backgrounds B/S of DYB,LA ~ 0.5% B/S of Far ~ 0.2% Site Survey Topography: Completed Geological Survey: Completed Geological Physical Survey: Completed Bore-Hole Drilling: Oct.~Dec.

Muon Simulation: 

Muon Simulation MUSIC simulation Rock density 2.6 g/cm3

A Versatile Site: 

A Versatile Site Fast measurement: One near site + mid site Sensitivity ~ 0.03 in a one year run 40 ton/site, reactor error 0.7% Full operation: (Goal) Two near sites + Far site (sin2213 < 0.01) Mid site + Far site (sin2213 ~ 0.01) Two near sites + Mid site + Far site (sin2213 < 0.01) Different systematics


Detector Vertical, cylindrical modules Easy to fabricate Easy to calibrate Size limited by tunnel cross section Multiple modules to control systematics and gain enough statistics. Three-layer structure: I. target: Gd-loaded scintillator, 20 ton II. gamma catcher: normal scintillator, 45cm III. Buffer shielding: mineral oil, ~45cm Possibly with reflection on top and bottom ~200 8”PMTs mounted in oil


Veto 2m+ water shielding (neutron produced in rock and gammas) Water cherenkov detector Another muon veto (plastic scintillator or RPC) outside the water shielding. > 99.5% efficiency.


Background Radioactivity: PMT glass, Rock, Radon in the air, etc Neutron Singles and Fast neutron backgrounds Neutrons produced in rock and water shielding (99.5% veto efficiencey) Cosmogenic isotopes 8He/9Li Cross section measured at CERN (Hagner et. al.) Can be measured in-situ, even for near detector with muon rate ~ 10 Hz. The above number is before shower muon cut.


Systematics Residual systematic error: ~ 0.2% Statistical Error (3 years): 0.2% Backgrounds: B/S ~ 0.6% No Vertex cut. Residual detection error is dominated by the neutron energy cut at 6 MeV, arises mainly from energy scale uncertainties. It is ~0.2%, suppose 1% energy scale error at 6 MeV. Positron energy cut negligible.


Sensitivity 90% confidence level DYB detector baseline 360m 40 ton B/S ~0.5% LA detector baseline 500m 40 ton B/S ~0.5% Far detector 1900m to DYB cores 1600m to LA cores 80 ton B/S ~0.2% Three-year run (2009-2011) 0.2% statistical error Detector residual error 0.2%

IHEP Detector Prototype: 

IHEP Detector Prototype 2-layer cylindric detector, 0.5 ton Gd-doped LS surrounded by 5 ton oil, 45 PMTs. Mounting PMT now.

Aberdeen Tunnel Exp.: 

Aberdeen Tunnel Exp. Hong Kong University & Chinese University of Hong Kong. Started in Jun. 2005 ~ 240m Overburden To study cosmic muon, neutron production, possibly cosmogenic isotopes. Similar rock as Daya Bay

Geological Survey: 

Geological Survey Topography Survey, done Geological Survey, done Geological Physical Survey, done High Resolution electric resistance seismic reflection Micro gravity measurement Bore hole drilling, Oct.~Dec.

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