1. ,,,,, The Daya Bay Reactor Neutrino Experiment Liangjian Wen On behalf of the Daya Bay Collaboration Institute of High Energy Physics Daya Bay Detectors Known: Unknown: LA: 40 ton Baseline: 500m Overburden: 112m Muon rate: 0.73Hz/m 2 Far: 80 ton 1600m to LA, 1900m to DYB Overburden: 350m Muon rate: 0.04Hz/m 2 DYB: 40 ton Baseline: 360m Overburden: 98m Muon rate: 1.2Hz/m 2 calibration system PMT Inner acrylic vessel (3m φxH) Stainless steel vessel Bottom reflector Top reflector 5m Mineral Oil LS Gd-LS Outer acrylic vessel (4m φxH) 5m Daya Bay experiment will use 200 ton 0.1% Gd-doped LS and 200 ton normal LS Gd-TMHA + LAB + 3g/L PPO + 15mg/L bis-MSB To ensure IDENTICAL detectors, all Gd-LS will be produced in multiple 4-ton batches and mixed in reservoir on-site. March 2009, a batch of 4 ton Gd-LS was produced successfully. LS production has been started in Oct. 2010 0.1% Gd-LS fluor-LAB Gd-LAB LS hall move SSV SSV sits in pit clean SSV inside insert bottom reflector insert outer AV insert Inner AV close outer AV lidtest Gd-LS filling probe lift PMT ladder install top reflectorclose SSV lidinstall ACUs Waterproof 8” PMTs: Potting and production finished. Water filtration and circulation system ready for installation. Have begun installing Tyvek and PMTs. Production and testing for all 1600 RPC s have been completed. More than 85% of RPC modules (2 RPCs x 4 layers) have been assembled and most of them tested. Modules for DYB hall will be ready soon. Support structure for DYB hall has been installed and tested. Gas system RPC module 2 near + far (3 years) arXiv:0907.1896: actual dates differ ● Shenzhen 55km Hong Kong Goal: Sin 2 2 θ 13 < 0.01 @ 90% CL in 3 years Redundancy is a unique feature for this experiment: Identical antineutrino detector modules to reduce errors and cross check. Multiple muon veto: Two zones of Cerenkov detector + RPC at the top. Total efficiency > (99.5  0.25) %. Daya Bay Layout Daya Bay Sensitivity Liquid Scintillator 5x40ton Gd-LS storage tank 2x200 ton storage pool Mixing N2 room Filling QC room LS hall layout Target mass measurement Detectors Assembly October 2010, first AD pair complete, Dry-Run tests finished October 2010, Daya Bay Near Hall Occupancy Daya Bay Hall: data taking, Fall 2011 Ling Ao and Far Halls: data taking, Fall 2012 Tentative Schedule 2012 … Reach the goal ! Water Cerenkov Detector ProgressRPC Detector Progress Daya Bay Experiment Is Hunting for θ 13 Neutrino mixing: where, Value of θ 13 is critical for studying CP violation and neutrino mass hierarchy. If Sin 2 2 θ 13 <0.01, long baseline experiments with conventional beam have little chance to determine CP violation. Determining θ 13 by observing electron antineutrino disappearance at reactor. Clean signal, only related to θ 13. Relative measurement with near and far detectors. Near Far The 11 th International Workshop on Next generation Nucleon Decay and Neutrino Detectors Toyama, Japan December 13 –16, 2010 Light from LEDs can be observed as well as Cherenkov light caused by cosmic ray muons passing acrylic. calibration LED PMT Charge (PE) with LED flashing LED Flashing Dry Run of the first AD pair Muon Off-axis LED Consistent performance of AD pair LED ACU A full end-to-end test of the fully instrumented Antineutrino Detectors prior to filling them with liquid scintillator. Double pulse LED to mimic events