【正文】 ?1 ?2 ?3 q12太陽中微子振蕩 q23大氣中微子振蕩 q13 ? mi ? Current Knowledge of q13 Direct search PRD 62, 072022 Allowed region et al., :012103 . GonzalezGarcia et al., JHEP1004:056,2022 ? No good reason(symmetry) for sin22q13 =0 ? Even if sin22q13 =0 at tree level, sin22q13 will not vanish at low energies with radiative corrections ? Theoretical models predict sin22q13 ~ % An experiment with a precision for sin22q13 less than 1% is desired model prediction of sin22q13 Experimentally allowed at 3s level 大亞灣反應(yīng)堆中微子實驗 ? 用大亞灣反應(yīng)堆測量 q13是我國粒子物理發(fā)展的一個重大機遇： – 功率高（世界第二） – 周圍有山，便于建設(shè)地下實驗室以屏蔽宇宙線本底 – 造價較低，沒有根本的技術(shù)困難 ? 世界各國共有 8個實驗建議，三個正在進行中 ? 難點：精度較過去提高一個量級 ? 我們的突破：獨特設(shè)計 +環(huán)境優(yōu)勢 ? 達到精度要求 Reactor neutrino exp. ? Clean signal, no cross talk with ? and matter effects ? Relatively cheap pare to accelerator based experiments ? Can be very quick ? Provides the direction to the future of neutrino physics Reactor experiments: Pee ? 1 ? sin22q13sin2 () ? cos4q13sin22q12sin2 () Long baseline accelerator experiments: P?e ≈ sin2q23sin22q13sin2() + cos2q23sin22q12sin2() ? A(r)?cos2q13sinq13?sin(?) How Neutrinos are produced in reactors ? The most likely fission products have a total of 98 protons and 136 neutrons, hence on average there are 6 n which will decay to 6p, producing 6 neutrinos Neutrino flux of a mercial reactor with 3 GWthermal : 6? 1020 /s ?nepe ??? ??1040 keV Neutrino energy: Neutrino Event: coincidence in time, space and energy ?? ????? epnne mMMTTE )(? Neutrino detection: Inverseβ reaction in liquid scintillator MeV: Threshold ?? t ? 28 ?s(% Gd) n + p ? d + g ( MeV) n + Gd ? Gd* + g (8 MeV) Reactor Experiment: paring observed/expected neutrinos: Precision of past exp. ? Reactor power: ~ 1% ? Spectrum: ~ % ? Fission rate: 2% ? Backgrounds: ~13% ? Target mass: ~12% ? Efficiency: ~ 23% Typical precision: 36% We need a precision of ~ % Currently Proposed sites/experiments Site (proposal) Power (GW) Baseline Near/Far (m) Detector Near/Far(t) Overburden Near/Far (MWE) Sensitivity (90%CL) Angra dos Reis (Brazil) 300/1500 50/500 200/1700 ~ Double Chooz (France) 150/1067 10/10 60/300 ~ Daya Bay (China) 360//500/1800 40//40/80 260/260/910 ~ Reno (S. Korea) 150/1500 20/20 230/675 ~ How to reach 1% precision ? ? Increase statistics: – Powerful nuclear reactors(1 GWth: 6 x 1020 ??e/s) – Larger target mass ? Reduce systematic uncertainties: – Reactorrelated: ? Optimize baseline for best sensitivity and smaller residual errors ? Near and far detectors to minimize reactorrelated errors – Detectorrelated: ? Use “Identical” pairs of detectors to do relative measurement ? Comprehensive program in calibration/monitoring of detectors ? Interchange near and far detectors (optional) – Backgroundrelated ? Go deep to reduce cosmicinduced backgrounds ? Enough active and passive shielding Layout ? Nearfar cancellation ? Two near sites and one far sites connected by ~3000 tunnel ? Event rate： ~1200/