Low Energy Neutrino Physics at the Kuo-Sheng Reactor Laboratory in Taiwan  Overview of TEXONO Collaboration  Kuo-Sheng Reactor Neutrino Laboratory  Results on Neutrino Magnetic Moments  Status on Neutrino-Electron Elastic Scattering  R&D projects towards Neutrino-Nucleus Coherent Scattering ( coupled with H.Wong’s talk )  Summary Lin,, Shin-Ted/ 林興德 On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration Institute of Physics, Academia Sinica / TAUP2007,sendai Japan 

TEXONO Collaboration Collaboration : Taiwan (AS, INER, KSNPS, NTU) ; China (IHEP, CIAE, THU, NJU) ; Turkey (METU) ; India (BHU) ; Korea (KIMS) Program: Low Energy Neutrino & Astroparticle Physics  Kuo-Sheng (KS) Reactor Neutrino Laboratory  oscillation expts.  m  0  anomalous properties & interactions  reactor : high flux of low energy electron anti-neutrinos  physics full of surprises, need intense -source ※ study/constraint new regime wherever experimentally accessible ※ explore possible new detection channels

Kuo-Sheng Nuclear Power Plant KS NPS-II : 2 cores  2.9 GW KS Lab: 28 m from core#1

Kuo Sheng Reactor Neutrino Laboratory Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics Front View (cosmic veto, shielding, control room …..) Inner Target Volume

Reactor Neutrino Spectrum  /fission 235 U: U: Pu: Pu:0.4 U (n,  ) 1.2  e ) ~ 6.4 X / sec*cm 2 Reactor Operation Data

R&D :  Coh. ( N)  T < 1 keV Results on  ( e ~ keV   d  dT)   >> (d  dT) SM  T<<E  d  dT  ∝ 1/T  T << E  d  dT depends on total  flux but NOT spectral shape On-Going Data Taking & Analysis  SM  ( e)  T > 3 MeV Reactor Neutrino Interaction Cross-Sections massqualityDetector requirements

KS Experiment: Period I, II, III,IV,V Detectors FADC Readout [16 ch., 20 MHz, 8 bit] ULB-HPGe [1 kg] CsI(Tl) Array Multi-Disks Array [few Tbs]

8 Neutrino Electromagnetic Properties : Magnetic Moments fundamental neutrino properties & interaction ; necessary consequences of neutrino masses/ mixings Astrophysics bound on   –  B  however, model dependence Study of anomalous  e scattering is valid for - both Dirac/Majorana - both Diagonal/Transition   i j Minimally Extended Standard Model: However, many models can enhance it significantly ( M, W R …..)

Magnetic Moment KS  simple compact all-solid design : HPGe (mass 1 kg) enclosed by active NaI/CsI anti-Compton, further by passive shielding & cosmic veto  selection: single-event after cosmic-veto, anti-Comp., PSD

Data Analysis  TEXONO data (570.7/127.8 days of Reactor On/OFF)  background comparable to underground CDM experiment : ~ 1 day -1 keV -1 kg -1 (cpd)  DAQ threshold 5 keV analysis threshold 12 keV  Combined all information   i / f Before/After cuts Spectrum ; SM    Reactor On/Off  e ( SM)   e 2  e    +/ - i f i f ff             

11 Systematic effects Best-fit  The limit based on 570.7/127.8 days of Reactor ON/OFF:   e ) <7.4 X  B (90% PRD Results on neutrino magnetic moment  e ( SM)    e 2  e           e X  B    e 2 = ־ 0.53 ± 0.59(stat.) ± 0.18(sys.)

Search of  at low threshold  high signal rate & robustness: Gemma prelim. Result:   e ) <5.4 X  B (90% Neutrino radiative decay

13 e e scattering However, SM >>MM at few MeV ! The differential cross section can be represented SMMM

CsI(Tl) Array (~200 kg) :  e) Z =40 cm Single Crystal Q L Vs Q R (Raw Data) Region of Interest for SM  e) Z = 0 cm 208 Tl 40 K 137 Cs Data analysis under way.. (40000/12000 day-kg for ON/OFF in PII to PV)

15 Status of neutrino-electron scattering Background understanding and suppression --Multiple-hit analysis ( Cosmic ray tagged,  cascades of 208 Th ) =>  sin 2  w of reactor ON/OFF  X 3 data  Global analysis of all spectra Expect:

 a fundamental neutrino interaction never been experimentally- observed ; a test of standard model ( T. Rashba’s talk )  an important interaction/energy loss channel in astrophysics media  R & D on an ULEGe towards (kg-scale ; 100eV threshold ; 1cpd) experiment : allow for CDM search ( H.Wong’s talk ) & improve the neutrino magnetic moment [   search  ~  B ] Neutrino-Nucleus Coherent Scattering

17  Kuo-Sheng Neutrino Lab.:  Modular & Flexible Design  Physics Data Taking since 2001 ※ Unique HPGe Low Energy Data ※ Bkg Level ~ Underground CDM Expment  Results published on     ( PRL 03;PRD 07 )& reactor e ( PRD 05 ) and axion ( PRD 07 HM Chang’stalk )  Diversified Program in Parallel Main Thrust on  ~200 kg CsI(Tl) [  ( e) …]  ULEGe: for  coh ( N) + CDM ( H.Wong’s talk ) Summary & Outlook