1 / 32

Neutrino Physics and Dark Matter Physics with Ultra-Low-Energy Germanium Detector

Lin, Shin-Ted/ 林欣德 On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration Institute of Physics, Academia Sinica / @ 5th Italian-Sino Workshop on Relativistic Astrophysics. Neutrino Physics and Dark Matter Physics with Ultra-Low-Energy Germanium Detector.

vilina
Download Presentation

Neutrino Physics and Dark Matter Physics with Ultra-Low-Energy Germanium Detector

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lin, Shin-Ted/ 林欣德 On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration Institute of Physics, Academia Sinica / @ 5th Italian-Sino Workshop on Relativistic Astrophysics Neutrino Physics and Dark Matter Physics with Ultra-Low-Energy Germanium Detector • Overview of TEXONO Collaboration • Kuo-Sheng Reactor Neutrino Laboratory • Results on Neutrino Magnetic Moments & status on Neutrino-Electron Elastic Scattering • Physics & Requirements for ULE-HPGe • R&D projects on ULE-HPGe Prototypes • Plans

  2. TEXONO Collaboration Collaboration : Taiwan(AS, INER, KSNPS, NTU) ; China(IHEP, CIAE, THU, NJU) ; Turkey(METU) ;India(BHU) Close Partnership with :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 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. 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 Under Analysis • SM s(ne) • T > 3 MeV • R&D : • Coh. (nN) • T < 1 keV Results: • mn(ne) • T ~ 1-100 keV

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

  8. fundamental neutrino properties & interaction ; necessary consequences of neutrino masses/ mixings Astrophysics bound on mn ~ (10-10 – 10-12mB) however, model dependence 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 • n-e scattering with mn • 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 Data Analysis • TEXONO data • 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) + ke Fe (mn) n

  11. Systematic effects Best-fit Results on neutrino magnetic moment • 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 % • more data • Global analysis of all spectra Expect:

  16. “Ultra-Low-Energy” HPGe Detectors • ULEGe – developed for soft X-rays detection ; easy & inexpensive & robust operation • Prototypes built and studied : • 5 g @ Y2L • 4 X 5 g @ KS/Y2L • 10 g @ AS/CIAE • Segmented 180 g @ KS • PC-500 g single element @AS • Physics for O[100 eV threhold1 kg mass1 cpd detector]: • nN coherent scattering • Low-mass WIMP searches • Improve sensitivities on mn [ mnsearch  ~10-11mB ] • Implications on reactor operation monitoring • Open new detector window & detection channel available for surprises

  17. ULEGe-Prototype built & being studied : 5 g 10 g 4 X 5 g Segmented 180 g with dual readout

  18. Neutrino-Nucleus Coherent Scattering A fundamental neutrino interaction never been experimentally-observed • s  ~N2applicable at En<50 MeV ( Take Q.F. =0.25, S/N >1 at 250 eV of threshold; At threshold 100 eV-> 11 count /day/ kg) • a sensitive test to Standard Model • an important interaction/energy loss channel in astrophysics media • a promising new detection channel for neutrinos, relative compact detectors possible (implications to reactor monitoring) • involves new energy range at low energy, many experimental challenges & much room to look for scientific surprises

  19. Characteristics of WIMP signal • Scattering off nuclei • A2 dependence • coherence loss • relative rates • MW relative to MN • large MW- lose mass sensitivity • if ~100 GeV • Present limits on rate • WIMP mass if not too heavy • different targets • accelerator measurements • galactic origin • annual modulation • directional courtesy of Gaitskell Vary MW for MN=73 from Jungman et al. dR/dER recoil energy, ER (keV)

  20. Sensitivity Plot for CDM-WIMP direct search • Low (<10 GeV) WIMP Mass / Sub-keV Recoil Energy : • Not favored by the most-explored specific models on galactic-bound SUSY-neutralinos as CDM ; still allowed by generic SUSY • Solar-system bound WIMPs require lower recoil energy detection • Other candidates favoring low recoils exist: e.g. non-pointlike SUSY Q-balls. • Less explored experimentally

  21. Yang-Yang Underground Laboratory • Operated by KIMS Collaboration, 700 m of rock overburden in east Korea • flagship program on CsI(Tl) for CDM searches • TEXONO  Install 5 g ULB-ULEGe at Y2L ; Study background and feasibility for CDM searches ; may evolve into a full-scale O(1 kg) CDM experiment Y2L

  22. Evaluation of Selection Efficiency: • Select clean sample ofphysicsevents with cosmic-ray and anti-Compton tags • Study survival probabilities of these with the independent selection cuts on Ge-signals • Good efficiency > 200 eV for low background KS data with 4X5 g

  23. Sub-keV Background Measurements & Comparisons 1 kg 5 g 4 X 5 g • Similar background at KS & Y2L for same detector • Apparent difference between 5 g & 1 kg at T> 5 keV due to scaling with surface area instead, reproduced in simulations • Best Background with 4X5 g comparable to CRESST-1 after corrections due to quenching factor • Intensive studies on background understanding under way

  24. Results on WIMP Spin-Independent Cross Section Limits & Sensitivities Standard conventional analysis – Maximum gap method ; Optimal Interval method

  25. WIMP Spin-dependent Cross Section Limits & Sensitivities Allowed regions of WIMP-nucleon couplings (proton and neutron) with a WIMP mass of 5 GeVc^-2, at 90%C.L WIMP-neutron cross section

  26. Backgrounds: cosmic rays and natural radioactivity WIMP scatters (< 1 evts /10 kg/ day) swamped by backgrounds ( > 106 evts/kg-d) Radioactive Nuclides in solids, surroundings 238U, 232Th chains, 40K Cosmic Rays Fast muons Radioactive Nuclides in atmosphere Airborne Radioactivity222Rn Radioactive Nuclides in detector, shield (especially 222Rn daughters, including 210Pb t1/2=22 years) Slow muons Shield contaminants Neutron capture (α, n) Electrons Muon capture Photo fission Spontaneous fission Gammas (α, n) Neutrons courtesy of S. Kamat

  27. R&D Program towards Realistic O(1 kg) Size Experiments (bothnN& CDM) : • measure & study background at sub-keV range at KS & Y2L ; design of active & passive shielding based on this. • compare performance and devise event-ID (PSD & coincidence) strategies of various prototypes • devise calibration & efficiency evaluation schemes applicable to sub-keV range • measure quenching factor of Ge with neutron beam • study scale-up options ULEGe-detector • Keep other detector options open

  28. Single Readout Event ID– correlate two channels with different gains & shaping times e.g. 4 X 5 g Sampling of Specific Range for non-trigger-Channel 2 – i.e. look for +ve fluctuations at specific and known times Energy as defined by trigger-Channel 1 Noise Signal Ch #1 : Ch #2 :

  29. Dual Readout Event ID– correlate anode/cathodes in amplitude & timing e.g. Peak Position Correlations between Electrodes Seg. 180 g Noise Signal Cathode : Anode :

  30. Quenching Factor Measurement for Ge at CIAE’s Neutron Facilities: With 13 MV Tandem • Goals for 2008 Runs : • Use actual ULEGe 100-eV detector • Use lower energy neutron beam with a smaller tandem

  31. p S1 S0 Detector Scale-up Plans: Most of energy deposited in the surface. A larger detector have a better g suppression . • 500-g, single-element, modified coaxial HPGe design, inspired by successful demonstration of Chicago group (nucl-ex/0701012) • Dual-electrode readout and ULB specification • Arrived in April 2008 @AS.

  32. Summary & Outlook • An O[100 eV threshold1 kg mass1 cpd detector] has interesting applications in neutrino and dark matter physics, also in reactor monitoring • Open new detector window & detection channel : potentials for surprise • Mass Scale-Up: recent demonstration of realistic design • Threshold– ~300 eV at hardware level, intensive studies on software techniques to aim at ~100 eV, & on their stabilities and universalities • Prototype data at reactor already provide competitive sensitivities for WIMP search at mass<10 GeV . • Sub-keV Background understanding and suppression – under intensive studies

More Related