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Study of neutrino-electron scattering with CsI(Tl) crystal array at Kuo-Sheng Reactor Laboratory

This study presents the analysis of neutrino-electron scattering using a CsI(Tl) crystal array at Kuo-Sheng Reactor Laboratory. It covers the physics of neutrino-electron interaction, the configuration of the CsI(Tl) detector, and data analysis techniques.

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Study of neutrino-electron scattering with CsI(Tl) crystal array at Kuo-Sheng Reactor Laboratory

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  1. Study of neutrino-electron scattering with CsI(Tl) crystal array at Kuo-Sheng Reactor Laboratory Lin Shin-Ted (On behalf of the TEXONO Collaboration)Academia Sinica, Taiwan @NSYSU Feb. 2005 • Physics with neutrino-electron interaction • Period -II configuration on CsI(Tl) detector • Data Analysis Techniques ※ Cuts ※ Cut summary • Background Understanding (ZYF’s input) • Results (Prelim.) Taiwan EXperiement On NeutrinO http://hepmail.phys.sinica.edu.tw/~texono/

  2. g g g For (ne-e), both NC & CC and their interference term contribute

  3. Reactor Neutrino Interaction Cross-Sections Reactor : high flux of low (MeV range) energy ne On-Going Data Taking:4SM s (ne) 4T > 3 MeV R&D:4Coh. (nN) 4T< 1 keV Results & More Data:4mn (ne) 4T~ 1-100 keV

  4. Kuo-Sheng Reactor Neutrino Laboratory Front Gate Front View (cosmic vetos, shieldings, control room …..) Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics Inner Target Volume

  5. Period-2 CsI(Tl) Array : 186 kg, 93 crystals Period II : Jan.28, 2003 – Jan.08 2004 ( ~ 50 days OFF 130 days ON) Single Crystal QL Vs QR (Raw Data) Z = 0 cm Z =40 cm 208Tl 40K 137Cs Region of Interest for SMs(ne)

  6. CsI(Tl) Array : Highlights • 40 cm length; 186 kg mass (longest commercial prod.) • Energy+3D info: 10% FWHM @ 660 keV Z-position resolution is 2 cm @ 660 keV s(z) <2 cm @ E>250 keV • Detector Threshold 3 MeV • Range of O (0.0407 cpd) [counts/kg/day] > 3 MeV background • PSD for g/a : > 99% Data Volume : Total > 250 / 50 days ON/OFF • Goals: • Commission 500kg target on-site • DAQ with large dynamic range

  7. Data Analysis Techniques No Cut: Energy Spectrum Defining Cuts: 1] General Cuts –a) No Cut energy spectrumb) Single Event Hit & Single Crystal Hit c) Cosmic ray Cut d) Rough Z-pos. cut SEH, SCH SEH, & SCH SEH, SCH, & Cosmic SEH, SCH, Cosmic-ray, & Z-pos SEH, SCH SEH, SCH SEH, SCH

  8. Data Analysis Techniques Defining Cuts:2] Special Cuts – a) Alpha Event Cut(having fast decay time) Check-Alphas are located around 2 MeV Select-event having Time average less than 40 [Nucl. Instrum. Methods A 523, 116 (2004)] Normal Event Pulse Alpha Event Pulse A; .

  9. Data Analysis Techniques Defining Cuts:3] Special Cuts – a) Double Event Cut(Left side double pulse) b – a pulse ! • 232Th series: • 212Bi(β-, 60.6min, 64%) → 212Po(α, 304ns) → 208Pb

  10. Data Analysis Techniques Defining Cuts:4] Special Cuts – a) Double Event Cut(Right side Double Pulse)

  11. Data Analysis Techniques 40cm long crystal No cut Defining Cuts:3] Z-position Cut – Select – Both side peak mean initially taken as 0 & 40 ! 0 cm 40 cm Narrow Pulse Normal Pulse AlphaPulse

  12. Cut Summary Cut Type All energy Above 3 MeVEfficiency (Suppression) (Suppression) [1] Raw data 1.00 1.00 1.00[2] Cosmic ray 0.11 0.88 0.93[3] anti-Compton 0.70 0.86 0.99[4] Single Trigger 0.01 0.02 0.99[5] Alpha 0.10 0.83 1.00[6] Double Pulse 0.11 0.38 0.99 (Left side & Right side) * Z-position cut is not applied !!

  13. Period-II CsI(Tl) Array : Results (Prilim.) OFF/ON DATA Energy Spectrum of recoil electron 137Cs (661 keV) 137Cs (661 keV) 40K (1461 keV) 40K (1461 keV) 208Tl (2615 keV) 208Tl (2615 keV)

  14. Background Understanding Prospects:- • Estimate the abundance of 238U and 232Th • Figure out the contribution of the two chains to the spectrum of the background

  15. 232Th Decay chain • α- α events Selection: • Simply choose α events and inspect the time interval between two adjacent ones • Cuts:Cosmic ray veto, Single hit, delay time<1s 220Rn --(55.6 s Ea=6.405MeV)-> 216Po--(0.145 s Ea=6.907MeV-> 212Pb • Results: • Delaytime • T1/2=0.153 sec. • Energy: • 6.405MeV: 3424.1KeV • QF: 1.87 • 6.907MeV: 3775.2KeV • QF: 1.83

  16. Background Understanding • From tagging event by event beta-alpha rate 0.43/day/kg alpha-alpha rate 0.71 /day/kg • Results: Above 3 MeV 0.0043 /day/kg Above 3.5 MeV 0.0042 /day/kg - delayed coincidence

  17. Results (Prilim.) OFF DATA(~3000 kg.days) Energy Spectrum of recoil electron 137Cs (661 keV) Above 3 MeV Counts/day/kg = 0.0116 (SM) Counts/day/kg = 0.0318 Above 3.5 MeV Counts/day/kg = 0.00574 (SM) Counts/day/kg = 0.00617 40K (1461 keV) 208Tl (2615 keV) 4 cm zpos (both side) cut !! * 42 Crystals (40 cm.) * Mass 67.2 kg * Data set 46 days OFF period

  18. Period-IICsI(Tl) Array : Results (Prelim.) The Estimate of BKG Suppression >3 MeV * Cosmic ~ one order * From Veto to All Cuts> Two order * 80kg All Cuts to ON-OFF ~ One order * S/B ratio (integral > 3 MeV) = 1/ 2.8 (->2.4) * D = (ds/s) = 40 %~ 2.3s measurement ! 10500 kg-days ON-period3200 kg-days OFF-period Differential Event Count for CsI(Tl)

  19. World status ! General conclusion is that a 1% measurement is well-worth pursuing ! “There is NOT YET any real measurement of reactor neutrino expt”. TEXONO NuTeV Qw(Cs) Czarnecki & Marciano (2000) E158 Run I+II (Preliminary) PDG2002 Measurements of sin2qw as a function of Q. The curve shows the Standard Model expectation

  20. World status ! Characteristics of the previous and current neutrino-e scattering experiments Expected Sensitivities : The accuracy of s(nee) drop down to 20% “Sin2qW was observed but there is NOT YET any real measurement for reactor neutrino”.

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