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Study of Neutrino-Electron Scattering with CsI(Tl) Scintillating Crystal Detector

Study of Neutrino-Electron Scattering with CsI(Tl) Scintillating Crystal Detector. Muhammed Deniz 1,2 1: METU, Ankara, Turkey 2: IoP, Academia Sinica, Taiwan On behalf of TEXONO collaboration. @ 2006 Workshop on the Underground Experiment – Extension of KIMS + TEXONO Collaboration.

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Study of Neutrino-Electron Scattering with CsI(Tl) Scintillating Crystal Detector

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  1. Study of Neutrino-Electron Scattering with CsI(Tl) Scintillating Crystal Detector Muhammed Deniz1,21: METU, Ankara, Turkey2: IoP, Academia Sinica, Taiwan On behalf of TEXONO collaboration @ 2006 Workshop on the Underground Experiment – Extension of KIMS + TEXONO Collaboration • TEXONO Physics Program on CsI(Tl) Detector • Shielding and CsI(Tl) Detector Design • Data Analysis Techniques • Cut Summary • Background Understanding and Suppression • Status and Plans

  2. TEXONO Physics Program on CsI(Tl) detector e + e-e+ e- CsI(Tl) (186 kg) : • attempt a measurement of Standard Model (ee-) sinw at MeV range Region of Interest for e -ve scattering • Uncertainties in the low energy part of reactor neutrino for SMee  higher energies (T>2 MeV)

  3. KS Expt. : Detector Configuration 16 ch, 20 MHz, 8 bit

  4. 95 88 91 79 70 72 77 85 86 54 57 76 75 74 73 51 87 42 96 58 62 61 65 26 101 25 24 59 55 53 67 93 220 13 21 27 45 94 32 63 19 23 11 05 43 50 80 49 64 16 35 10 83 92 66 33 46 40 41 34 17 81 78 68 31 89 08 39 99 15 48 47 44 69 20 38 14 90 60 56 71 82 97 22 98 06 04 02 37 12 03 52 100 Plastic 20+20 cm-veto crys. 40 cm-veto crys. 40 cm-target crys. CsI(Tl) crystal layout (93 cry. 186 kg)

  5. CsI(Tl) Array : Highlights • Period IIData Volume : Total ~ 110 / 50 days ON/OFF • 186 kg mass;20+20 and40 cmlength(longest commercial prod.) CsI(Tl) crystals • Detector Threshold: 3 MeV • Energy:total light collection • z-position:the variation of the ratio • Energy &Z-position info: 10% FWHM @ 660 keV Z-position resolution is (z) = 2 cm @ 660 keV (z) <2 cm @ higher energies

  6. Normal Event Pulse Alpha Event Pulse Data Analysing Techniques - Defining Cuts • Alpha Event Cut • having fast decay time Checking: Alphas are located around 2 MeV Selection: Mean Time Method: tav vs. q and Double Charge Method: compare total charge with partial charge

  7. Definition: Selection: Both side peak means initially taken as 0 & 40. Cut: 4 cm from both sides 0 cm 40 cm Narrow Pulse Normal Pulse Data Analysis Techniques - Defining Cuts 40 cm long crystal No cut b)Z-position Cut:

  8. Data Analysis Techniques - Defining Cuts Veto cut: Reject Cosmic raySingle-hit cut: Anti Compton effectPSD cut : Alpha particleZ-pos cut : Both veto and S.H. effect

  9. BEFORE CORRECTION AFTER CORRECTION BEFORE CORRECTION AFTER CORRECTION Data Analysis Techniques -Calibration 2) SLOPE CORRECTION: 1) Z-POSITION CORRECTION: 3) ENERGY CORRECTION:

  10. 137Cs (662 keV) ON spectrum 0.441/day/kg in Period II 40K (1460 keV) 208Tl (2614keV) OFF spectrum 0.423/day/kg in Period II ON and OFF Energy Spectra *37 Crystals (40 cm) * Mass 59.2 kg *Basic cuts + Alpha cut + 4 cm Z-cut ON&OFF spectra in 3-8 MeV energy range OFF spectrum in all energy range

  11. Two Type : • Radioactive Contaminants [Decays of radioactive contaminants mainly232Th and238Uchainproduce background in the region of interest. • Estimate the abundance of 137Cs,238U and 232Th inside the detector. • Figure out the contribution of 238U and 232Thchains to the background. 2. Environmental Background [Cosmic Ray muons, Products of cosmic ray muons, Spallation neutrons and some radioactive elements like 60Co, 208Tl • Estimate the background related to cosmic rays due to inefficiency a suppression. • Understand and suppress the contribution of 208Tl to the background in region of 3-4 MeV. Background Understanding

  12. Background Understanding Radioactive Contaminants • IDEA:By monitoring the timing and position information related β-α or α-α events can provide distinct signature to identify the decay process and the consistency of the isotopes involved. Environmental Backgrounds • IDEA:multiple-hit analysis can give us very good understanding especially Tl-208and cosmic related background in the region of interest • cosmic • By comparing cosmic and not-cosmicmultiple-hit spectra. • By examining the pair-production phenomena in not-cosmicmultiple-hit spectra. • Tl-208 • By examining multiple-hit spectra as well as simulation of Tl-208 decaychain energies to understand/suppress backgroundin the region of 3-4 MeV.

  13. Intrinsic 137Cs Level 31.3 kg-day of CsI(Tl) data was analysed. 137Cs contamination level in CsI was drived ==> (1.55 ± 0.02 ) X 10-17 g/g

  14. T1/2 = (283 ± 37) ns. T1/2 = (163 ±8) ms α β α a a β T1/2 = (0.141± 0.006) s Intrinsic U and ThContamination Level Data:The total of 40 crystals with data size of 1725 kg·day was analyzed. Master Thesis results of Zhu Y. F. fromTsing Hua Univ. in Beijing (2006) ii)212Bi(b-,64%) → 212Po(a, 299ns) → 208Pb i) 214Bi(b-)→ 214Po(a,164ms) → 210Pb Selection:b-pulse followed by a large a pulse Selection: 1st pulse is g(b) shaped & 2nd pulse a shaped 232Th abundance = 2.3 ± 0.1 x10-12 g/g 238U abundance = 0.82 ± 0.02 x10-12 g/g iii) 220Rn(a) → 216Po(a, 0.15s) → 212Pb Selection:twoα events with time delay less than 1s 232Th abundance = 2.23 ± 0.06 x 10-12g/g

  15. 510 1170 1330 The Sources are external 2100 600 800 The Source is external Background Understanding via Multi Hit • Co-60 contamination • 1173.2keV 99.86% accompanied with 1332.5keV 99.98% • Tl Pair Production: One escape peaks • (~ 2105 + 511 keV) Cs-134 (n + 133Cs g134Cs) • 97.6% 605 keV; • 85.5% 796keV 2614keV 99.79 % accompanied with 583 keV 86% 510.8 keV 22.6% 860 keV with 12.4% The source is internal. • Cosmic induced neutrons can be captured by the target nuclei 133Cs. • Combination of Tl gammas can affect up to around 4 MeV

  16. Background Understanding – Tl-208 and Cosmic Inefficiency

  17. Study on Background in Statistically • To understand the contribution of cosmic rays to the background, ~ 926kg*day data was analyzed for cosmic and not-cosmic multi-hit as well as pair production.

  18. c2Analysis • There are two kinds of background events within our signal. • one is matching well with reference g-pulse (b-)and • the other is fast- falling (a)… Black –Recorded Pulse by FADC Green – Reference a pulse Red - Referenceg pulse TYPE I TYPE II Left side Right side Left side Right side ○ ○

  19. Red –b events Black – g events Cutting at this point, suppression 66%(.248/.727) c-square function c2Analysis

  20. The best fit of sin2qW : 0.37 ±0.13 at 3-8MeV 0.30±0.22 at 3.5-8MeV Preliminary Result of sin2qW Ph.D. Thesis results of Dr. Lin Shin Ted (2006) g

  21. Expected Accuracy of sin2qWwith data size 130

  22. Expected Result of Accuracy of e-e) and sin2qW

  23. Experiments Savannah Kurtchatov Rovno NUMU TEXONO Fluorocarbon 103 kg 3.1 0.78 0.1 53% Si(Li) 37.5 kg 0.6 5.2 0.008 49% CsI(Tl) cry. 186 kg 3.0 1.8 (expect) 0.1 <20% (goal) Target Fiducial Mass Thr. (MeV) Signal Evt./Day S / B Accuracy of (ee) Plastic scin. 15.9 kg 1.5 1.2 0.18 29%* CF4 gas 21 kg 0.9 1.77 0.2 50% “Our aim is to measure (ee) with <20% accuracy.” Our aim is to measure Sin2Wvaluewith<8%accuracy. TEXONO and World status ! Characteristics of the previous and current neutrino-e scattering experiments

  24. Thank you

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