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TEXONO Collaboration: Low Energy Neutrino Physics at Kuo-Sheng Reactor Laboratory in Taiwan

This paper provides an overview of the TEXONO Collaboration's research on low energy neutrino physics at the Kuo-Sheng Reactor Laboratory in Taiwan. It discusses their results on neutrino magnetic moments, preliminary results on neutrino-electron elastic scattering, and R&D projects towards neutrino-nucleus coherent scattering. The paper also includes a survey of other research programs and a summary and outlook.

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TEXONO Collaboration: Low Energy Neutrino Physics at Kuo-Sheng Reactor Laboratory in Taiwan

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  1. Lin,, Sin-Ted/ 林興德 On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration Insititute of Physics, Academia Sinica / 中央研究院@ 9th CIPANP 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 • Preliminary Results on Neutrino-Electron Elastic Scattering • R&D projects towards Neutrino-Nucleus Coherent Scattering • Survey of Other Research Program • Summary & Outlook

  2. TEXONO Collaboration Collaboration : Taiwan(AS, INER, KSNPS, NTU) ;China(IHEP, CIAE, THU, NJU) ;Turkey(METU) ;USA(UMD) ;India(BHU) Program: Low Energy Neutrino & Astroparticle Physics • Kuo-Sheng (KS) Reactor Neutrino Laboratory • reactor : high flux of low energy electron anti-neutrinos • oscillation expts.  mn0  anomalousnproperties & interactions • nphysics full of surprises , need intensen-source • study/constraint new regime wherever experimentally accessible • explore possible new detection channels • DiversifiedR&D Projects

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

  4. Kuo Sheng Reactor Neutrino Laboratory Front View (cosmic veto, shielding, control room …..) Inner Target Volume Fne(6.4 X 1012 /s ) n/fission 235U: 3.4 238U: 0.5 239Pu: 1.8 241Pu: 0.4 U (n,g) 1.2 Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics

  5. quality Detector requirements mass On-Going Data Taking & Analysis • SM s(ne) • T > 3 MeV • R&D : • Coh. (nN) • T < 1 keV Results & More Data: • mn(ne) • T ~ 1-100 keV Reactor Neutrino Interaction Cross-Sections

  6. KS Experiment: Period I, II, III Detectors CsI(Tl) Array ULB-HPGe [1 kg] FADC Readout [16 ch., 20 MHz, 8 bit] Multi-Disks Array [1 Tb*5]

  7. Magnetic Moment Searches @ KS Neutrino Electromagnetic Properties • simple compact all-solid design : HPGe (mass 1 kg) enclosed by activeNaI/CsI anti-Compton, further by passive shielding&cosmic veto • selection: single-event after cosmic-veto, anti-Comp., PSD

  8. Combined Analysis with all Information : • Denote • TEXONO data -1st results @PRL 90, 131802 (2003) . • background comparable to underground CDM experiment : ~ 1 day-1keV-1kg-1 (cpd) • DAQ threshold 5 keV analysis threshold 12 keV • The limit based on 570.7/127.8 days of Reactor ON/OFF: mn(ne) <7.2 X 10-11mB (90% CL) @ hep- ex /0605006

  9. Search of mn at low energy • high signal rate & robustness: mn>>SM [ decouple irreducible bkg  unknown sources ] T<<En ds/dT depends on totalfnflux but NOT spectral shape [ flux well known : ~6 fission-n~1.2 238Ucapture-n per fission ] Neutrino radiative decay

  10. nee scattering However, SM >>MM at few MeV ! The differential cross section can be represented

  11. Single Crystal QL Vs QR (Raw Data) Z = 0 cm 208Tl 40K 137Cs Region of Interest for SMs(ne) CsI(Tl) Array (~200 kg): s(ne) Data analysis under way .. (25000/8000 day-kg for ON/OFF in PI,II,III) Z =40 cm

  12. Preliminary Result Further analysis =>reduce the background • PSD on e/g in few MeV region • X 4 data • Background understanding and suppression (Cosmic ray, gcascades of 208Th, Pair Production) • Global analysis of all spectra Goal The best fit of based on 6500/ 3600 day*kg for Reactor of ON/OFF 0.37+- 0.13 at 3-8MeV 0.30+- 0.22 at 3.5-8MeV

  13. Standard Model Cross-Sections: Neutrino-Nucleus Coherent Scattering • a fundamental neutrino interaction never been experimentally-observed • s~N2applicable at En<50 MeV where q2r2<1 • a sensitive test to Standard Model (Say,with Q.F.=0.25; Bkg ~1 cpd; Threshold~100eV, the Signal-to-Background ratio~ 20) • an important interaction/energy loss channel in astrophysics media • a promising new detection channel for neutrinos, without strict lower bound onEn&the channel for WIMP direct detection ! • involves new energy range at low energy, many experimental challenges & much room to look for scientific surprises

  14. “Ultra-Low-Energy” HPGe Prototype • ULEGe – developed for soft X-rays detection ; easy & inexpensive & robust operation • Prototype : (I) 5 g ; (II) 4 X 5 g ; (III) 10 g ; (IV) segmented 20 g • threshold <100 eV after modest PSD [lowest achieved for bulk radiation detectors] • study feasibilities for 1-kg-ish detector fornN coherent scatteringand Dark Matter searches [ mnsearch  10-11mB ] 5 g 4 X 5 g Threshold < 100 eV

  15. TEXONO  KIMS @ Y2L Yangyang (襄陽) Lab (Y2L) min. 700 m of rock overburden • Install 5 g ULB-ULEGe at Y2L on January 2005 • Study background and feasibility for CDM searches • may evolve into a full-scale (1 kg) CDM experiment Sensitivity Plot for CDM-WIMP search with 1 kg ULEGe at 100 eV threshold ..

  16. Survey for other research program • Evaluateneflux at standard reactors \ Explore neflux enhancement in loaded reactor(e.g. with Cr)@Phys. Rev. D 72, 012006 (2005) • Looking for n-induced nuclear transition • Search for reactor axions * Reactor core has intense M1 transitions : e.g.7Li, 91Y, 97Nbetc. • Trace Radio-purity measured with AMS * develop quick\small sample techniques ( e.g. 40K 10-16 g/g)

  17. Summary & Outlook • TEXONO Collaboration:  Built-Up from Scratch & Maturing • Kuo-Sheng Neutrino Lab.: Established & OperationalModular & Flexible Design Physics Data Taking since June 01 ※ Unique HPGe Low Energy Data ※ Bkg Level ~ Underground CDM Expt • Results published on mn (Gn) & reactor ne • Diversified Program in Parallel Main Thrust on ~200 kg CsI(Tl) [s(ne) …] ULEGe:for scoh(nN) + CDM ;

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