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Low Energy Neutrino Physics at the Kuo-Sheng Reactor Laboratory in Taiwan

Lin,, Shin-Ted/ 林興德 On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration Institute of Physics, Academia Sinica / 中央研究院 @ TAUP2007,sendai Japan. Low Energy Neutrino Physics at the Kuo-Sheng Reactor Laboratory in Taiwan. Overview of TEXONO Collaboration

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Low Energy Neutrino Physics at the Kuo-Sheng Reactor Laboratory in Taiwan

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  1. Lin,, Shin-Ted/ 林興德 On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration Institute of Physics, Academia Sinica / 中央研究院@ TAUP2007,sendai Japan 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

  2. 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.  mn0  anomalousnproperties & interactions • reactor : high flux of low energy electron anti-neutrinos • nphysics full of surprises , need intensen-source • study/constraint new regime wherever experimentally accessible • explore possible new detection channels

  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 Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics

  5. Reactor Neutrino Spectrum Reactor Operation Data n/fission 235U:3.4 238U:0.5239Pu:1.8 241Pu:0.4 U (n,g) 1.2 F(ne) ~ 6.4X1012 / sec*cm2

  6. Reactor Neutrino Interaction Cross-Sections quality Detector requirements mass On-Going Data Taking & Analysis • SM s(ne) • T > 3 MeV • R&D : • Coh. (nN) • T < 1 keV Results on mn(ne) @T ~ 1-100 keV • (ds/dT)mn >> (ds/dT)SM • T<<En ds/dT∝ 1/T • T << En ds/dT depends on total fn flux but NOTspectral shape

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

  8. fundamental neutrino properties & interaction ; necessary consequences of neutrino masses/ mixings Astrophysics bound on mn ~ (10-10 – 10-12mB) however, model dependence Study of anomalous n-e scattering is valid for - both Dirac/Majorana n - both Diagonal/Transition mij Neutrino Electromagnetic Properties : Magnetic Moments Minimally Extended Standard Model: However, many models can enhance it significantly (nM, WR …..)

  9. Magnetic Moment Searches @ KS • 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

  10. 2 +/- F = e × .n + F f f + - F - e × n F f f = + - F - n F i i + - Data Analysis • TEXONO data (570.7/127.8 days of Reactor On/OFF) • background comparable to underground CDM experiment : ~ 1 day-1keV-1kg-1 (cpd) • DAQ threshold 5 keV analysis threshold 12 keV • Combined all information i / f Before/After cuts i / f F Spectrum ; Reactor On/Off +/ - n SM + m = = Fe (SM) + ke2Fe (mn) n

  11. Systematic effects Best-fit Results on neutrino magnetic moment n = Fe(SM) + ke2Fe(mn)(mn =ke X10 -10 mB) ke2 =־ 0.53 ± 0.59(stat.) ± 0.18(sys.) • The limit based on 570.7/127.8 days of Reactor ON/OFF: mn(ne) <7.4 X 10-11mB (90% CL) @ PRD 75 2007

  12. Neutrino radiative decay • Search of mn at low threshold • high signal rate & robustness: Gemma prelim. Result: mn(ne) <5.4 X 10-11mB(90% CL) @hep-ex0705.4576v1

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

  14. 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 .. (40000/12000 day-kg for ON/OFF in PII to PV) Z =40 cm

  15. Status of neutrino-electron scattering Background understanding and suppression --Multiple-hit analysis (Cosmic ray tagged, gcascades of 208Th ) => s(sin2qw) = 28 % @6900/2300day*kg of reactor ON/OFF • X 3 data • Global analysis of all spectra Expect:

  16. Neutrino-Nucleus Coherent Scattering • 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 [ mnsearch  ~10-11mB ]

  17. Summary & Outlook • 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 mn (Gn)(PRL 03;PRD 07)& reactor ne(PRD 05) and axion ( PRD 07HM Chang’stalk ) • Diversified Program in Parallel Main Thrust on ~200 kg CsI(Tl) [s(ne) …] ULEGe:for scoh(nN) + CDM (H.Wong’s talk)

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