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Status of the Measurement of AntiNeutrino-Electron Scattering In TEXONO Experiment

Status of the Measurement of AntiNeutrino-Electron Scattering In TEXONO Experiment. Muhammed Deniz 1,2 1: METU, Ankara, Turkey 2: IoP, Academia Sinica, Taiwan 2 nd Korea-China Joint Seminar on Dark Matter Search @ SNU. Outline. Neutrino-Electron Scattering

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Status of the Measurement of AntiNeutrino-Electron Scattering In TEXONO Experiment

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  1. Status of the Measurement of AntiNeutrino-Electron Scattering In TEXONO Experiment Muhammed Deniz1,21: METU, Ankara, Turkey2: IoP, Academia Sinica, Taiwan 2nd Korea-China Joint Seminar on Dark Matter Search @ SNU

  2. Outline • Neutrino-Electron Scattering • Highlights on CsI(Tl) Detector • Shielding and CsI(Tl) Detector Design • CsI(Tl) Detector Array • Event Selection Criteria and Cut Summary • Multi-Hit and Pair-Production Analysis • Single Hit Background Predictions • Future Plans and Conclusion • Theory • TEXONO Physics Program • TEXONO Experiment • Data Analysing Techniques • Background Understanding and Suppression Methods • Status and Results

  3. Neutrino-Electron Scattering Cross-Section e + e-e+ e-

  4. Neutrino-Electron Scattering Cross-Section e + e-e+ e-

  5. PDG 2007 “There is NO significant measurement at low energies especially with reactor anti-neutrino” sin2qW measurement in the World PDG table

  6. TEXONO Physics Program on CsI(Tl) detector e + e-e+ e- • attempt a measurement of Standard Model  (ee-)  sin2w at MeV range Measurement :Recoil Energyofe- • properties are not fully understood intense -source Reactor : high flux of low energy (MeV range) electron anti-neutrinos. CsI(Tl) (200 kg) : • Region of Interest for e - e scattering Big uncertainties of modeling in the low energy part of reactor neutrino for SMs(nee)higher energies (T>3 MeV)

  7. Kuo-Sheng Reactor Neutrino Laboratory Front Gate Front View(cosmic vetos, shieldings, control room …..) Control Room CsI(Tl) Detector Inner Target Volume & Shielding

  8. Detector Configuration

  9. CsI(Tl) (200 kg) Connecting Board KS CsI(Tl) Experiment Configuration Multi-Disks Array (several Tb) FADC Readout 16 ch., 20 MHz, 8 bit

  10. CsI(Tl) Array : Highlights • Detector Threshold: 3 MeV • Energy:total light collection z-position:the variation of the ratio Period IIData Volume (186 kg in mass): Total ~95 / 50 days ON/OFF Period IIIData Volume (200 kg in mass): Total ~190 / 40 days ON/OFF • Energy resolution info: 10% FWHM @ 660 keV • Z-position resolution is (z) = 2 cm @ 660 keV (z) <2 cm @ higher energies

  11. Cosmic Ray Veto (CRV) record the time gap between the last hit of veto and trigger signal. Single-Hit (SH) select only one hit and only one crystal fired at one time. Pulse Shape Discrimination (PSD) separate different pulse shapes from real signal. Z position cut from both sides 4 cm cut is applied to the 40 cm length crystals. Event Selection

  12. Alpha Cut • having fast decay time Checking: Alphas are located around 2.5 MeV Selection: • Mean Time Method: tav vs. q and • Double Charge Method: compare total charge with partial charge Normal Event Pulse Alpha Event Pulse Data Analysing Techniques - Defining Cuts

  13. PSD Cut : Double Event B Right side Double Pulse A Left side double pulse ( – pulse) Data Analysing Techniques - Defining Cuts

  14. P-II and P-III OFF CsI Energy Spectra with Various Cuts

  15. The Efficiency and Suppression Factors of Various Cuts Period-III Period-II

  16. 0.17 % 0.87 % 0.2 % 0.80 % The Stability Check Period - II Period - III Cut Efficiency Cut Efficiency Data Stabilty Data Stabilty

  17. The Stability Check 3-8 MeV Period - II Period - III OFF ON OFF ON

  18. P-II & P-III CsI Energy Spectra ON P-II and P-III OFF P-II and P-III

  19. A.Radioactive Contaminants • Decays of radioactive contaminants mainly232Th and238U decay chainproduce background in the region of interest. Estimate the abundance of 137Cs,238U and 232Th inside the detector. 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. B.Environmental Backgrounds • Cosmic Ray muons, Products of cosmic ray muons, Spallation neutrons and some radioactive elements like 60Co, 208Tl 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. - 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. Background Understanding

  20. Efficiencies, Measured Half-Livesand Contamination Level Published Zhu Y. F., et al., Nucl. Instr. and Meth. A 557 (2006) 490-500. 137Cs contamination level in CsI ==> (1.55 ± 0.02 ) X 10-17 g/g

  21. 208Tl beta with associated gammas energies deposit in one crystal. 232Th (decay chain) This can be negligible background in our background level of ~ 0.4 cpdin 3 - 5 MeV Estimate the background due to Intrinsic 208Tl 3a, 3b BR 36%

  22. takingcosmic/non-cosmic ratio for 2&3-hitenergy spectra Cosmic Inefficiency Pair production cosmic/non-cosmic ratio for 3-hit Tl-208 (3-4 MeV) 208Tlchain2-hitenergy spectra Simulation with angular correlation Environmental Background Understanding Nearly all crystals including 20+20 and 40 cm crystals data was analyzed.

  23. Etot = 3-4 MeV Etot = 1-2 MeV Etot = 2-3 MeV External Source(s) 511 keV 605 keV Background Understanding viaMulti Hit 2100 keV 796 keV 1173 keV 1332 keV • Co-60 • 1173.2keV 99.86% accompanied with 1332.5keV 99.98% • The background related to reactor. Mostly come from the dust. • Tl Pair Production:One escape peaks • (~ 2105 + 511 keV) Cs-134(n + 133Cs g134Cs) • 605 keV 97.6%; • 796keV 85.5% 510, 583 keV External Source(s) 2614 keV With the Q of beta decay at 2MeV Internal Source(s) 2614keV 99 % accompanied with 583 keV 85% 510.8 keV 23% 860 keV with 13% 860 keV • Cosmic induced neutrons can be captured by the target nuclei 133Cs. • Combination of Tl gammas can affect up to around 4 MeV

  24. Background Understanding: Due to Tl-208 and Cosmic Inefficiency

  25. Background Understanding: Due to Tl-208

  26. Tl-208 SH Estimation 3 - 3.5 MeV PIII-ON Period 583 keV g + 2614 keV g No z-cut 4 cm z-cut Best fit = 0.0444 ± 0.00407 c2 = 8.59/(nof=8) SH = 610.38 ± 55.90

  27. SH Background Prediction Due to Cosmic • = ON - OFF • = ON - (SH)pred. • = ON - BKG where T1 = (SH)not cos + (SH)cos and T2 = (MH)not cos + (MH)cos d(SH)pred < dOFF we win with this alternative approach … • Single Hit Prediction is made by using ON period data. We can improve accuracy profoundly since we have more than 100 days ON data in PII and 200 days in PIII and more for other periods …

  28. Ee-e+ Ee-e+ Ee-e+ Background Expectation via PAIR PRODUCTION 2 - HIT 3 - HIT q p q q p SH p

  29. Period-II e = 92.5% Period-III e = 86.5% Reactor OFF Period Period - II Period - III Energy (MeV) cosmic Tl-208/Cu cosmic Tl-208/Cu 54 % Tl 63 % 46 % 3.0 – 3.5 37 % Tl 3.5 – 6.5 ~ 100 - ~ 100 - 6.5 – 8.0 46 % 54 % Cu 47 % 53 % Cu Background Understanding via Multi-Hit

  30. SH Prediction via Multi-Hit for OFF Data Period - III Period - II OFF-(SH)pred.

  31. Period-II e = 92.6% Period-III e = 86.7% Energy (MeV) Single - Hit Prediction Single-Hit Prediction 3.0 – 3.5 963 ± 31 961 ± 31 921.6 ± 42.1 1762 ± 41.9 1721.2 ±63.9 282.2 ± 16.2 724 ± 26.9 292 ± 17.1 3.5 – 4.0 704.9±24.7 4.0 – 4.5 194 ± 13.9 196.3 ± 13.5 516 ± 22.7 489.3±20.6 4.5 – 5.0 141 ± 11.9 133.7 ± 11.1 349 ± 18.7 353.8 ±17.5 5.0 – 5.5 118 ± 10.8 94.9 ± 9.4 259.5±15.0 261 ± 16.2 5.5 – 6.0 81 ± 9 69.1 ± 7.9 202 ± 14.3 192.5±12.9 6.0 – 6.5 52.7 ± 6.9 173 ± 13.2 176.5±12.1 55 ± 7.4 6.5 – 7.0 80 ± 8.9 80.3 ± 8.3 194 ±13.9 150.2±11.2 158 ± 12.5 7.0 – 7.5 76 ± 8.7 76.7 ± 7.9 160.6±11.1 7.5 – 8.0 73 ± 8.5 61.4 ± 7.1 138 ± 11.7 134.6 ± 9.9 SH Prediction via Multi-Hit for ON Data

  32. sin2qW measurement for Period-II ON-BKG Sin2qW = 0.294 ± 0.0933

  33. sin2qW measurement for Period-III ON-BKG Sin2qW = 0.225 ± 0.113

  34. sin2qW measurement for Period-II + Period-III (ON-BKG)p2+p3 Sin2qW = 0.259 ± 0.0724

  35. Methods Period – III Period – II + III Period – II ON – OFF R = (1.614 ± 1.055) RSM Sin2qW = 0.319 ± 0.120 R = (0.8662 ± 1.111) RSM Sin2qW = 0.218 ± 0.184 R = (1.258 ± 0.7691) RSM Sin2qW = 0.275 ± 0.101 ON – SHpred R = (1.189 ± 1.083) RSM Sin2qW = 0.266 ± 0.148 R = (0.942 ± 0.9169) RSM Sin2qW = 0.229 ± 0.144 R = (1.044 ± 0.7011) RSM Sin2qW = 0.245 ± 0.103 ON – BKG R = (1.407 ± 0.7556) RSM Sin2qW = 0.294 ± 0.0933 R = (0.911 ± 0.707) RSM Sin2qW = 0.225 ± 0.113 R = (1.141 ± 0.5181) RSM Sin2qW = 0.259 ± 0.0724 TEXONO Status The Summary of cross section and Weinberg Angle Measurements with various methods

  36. n(n) - e- Scattering Cross-Section and sin2qW measurement in the world n-e- n-e- R = (1.141 ± 0.5181) RSM Sin2qW = 0.259 ± 0.0724 TEXONO

  37. s (%) = 0.60 sne(%) Expected Accuracy with data size For .sin2qW For .cross-section 28% 45% 32% 19% 15% 26%

  38. Status of P-IV Data – Very Preliminary ON P-IV

  39. Neutrino-Electron Scattering Cross-Section The Interferece Term

  40. “This will be the first significant results in the measurement of  (ee), Interference I (ee) term and sin2Wvalue at low energy with reactor neutrino”. • “Our aim is to measure  (ee) with < 15% accuracy”. • “Our aim is to measure sin2Wvaluewith< 10%accuracy”. • For this purpose • get more stable and in good condition data • understand the background further and develop suppression methods effectively. Conclusion

  41. Thank you

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