Weekly Journal Club for Medium Energy Physics at IPAS 2011/1/24 Stud St udies es on on Ne Neut utrino ino-El Elect ectron ron El Elastic c Sc Scattering ering in n the e St Stand ndard rd Mod odel el and nd Bey eyon ond ed Deniz 1, 1,2 Muhamm ammed 1: IoP, Academia emia Sinica, ica, Taiwan n 2: KTU & METU, , Turkey On behalf of TEXONO O Collab abora oration tion Institute itute of Physics, cs, Academia emia Sinica ica Taipei ei, , TAIWAN, AN, 24 Jan 2011
OUT OUT OUT UTLI UTLI UTLI LINE LINE LINE NE NE NE • e – e - Scattering Theory overview n e Theory overview Scattering – Motivation Motivation • TEXONO Physics Program TEXONO Physics Program • TEXONO Experiment TEXONO Experiment – CsI(Tl) Array CsI(Tl) Array Event Selection Event Selection & Data Analysis Outline Data Analysis Outline Background Understanding Background Understanding & Suppression Suppression Analysis Results Analysis Results • Cross Section Cross Section & EW EW Parameters Parameters – World Status World Status • with n e Probing New Physics Probing New Physics – NSI & UP NSI & UP with e – e - • Summary Summary 2/36 Studies on Neutrino-Electron Scattering
n e – e - Scattering Formalism A basic SM process with CC, NC & Interference n e + e - n e + e - Not well-studied in reactor energy range ~ MeV 3/36 Studies on Neutrino-Electron Scattering
Neutrino-Electron Scattering Cross-Section n e + e - n e + e - g A g V 1 1 0 . 0128 day kg 4/36 Studies on Neutrino-Electron Scattering
TEXONO Physics Program TEXONO Collaboration: TEXONO Collaboration: Taiwan Taiwan (AS,INER,KSNPS,NTU) (AS,INER,KSNPS,NTU) ; China (IHEP,CIAE,THU,NKU,SCU,LNU) China (IHEP,CIAE,THU,NKU,SCU,LNU) ; Turkey Turkey (METU, KTU) (METU, KTU) ; India India (BHU) (BHU) Program: Low Energy Neutrino & Program: Low Energy Neutrino & Astroparticle Astroparticle Physics Physics quality mass Detector requirements [3] Observable Spectrum Observable Spectrum Observable Spectrum with typical with typical with typical reactor neutrino “beam” reactor neutrino “beam” reactor neutrino “beam” Taiwan an [1] EX EXperimen riment On n [2] Neutrin rinO [1] Magnetic Moment Search at ~10 keV PRL 2003, PRD 2007 [2] Cross-Section and EW Parameters measurement at MeV range PRD 2010 n e N Coherent Scattering & WIMP Search at sub keV range PRD-R 2009 [3] 5/36 Studies on Neutrino-Electron Scattering
Kou-Sheng Reactor Power Plant KS NPS -II : 2 cores 2.9 GW KS NPS -II : 2 cores 2.9 GW KS NPS -II : 2 cores 2.9 GW Total flux about 6.4x10 12 cm -2 s -1 Total flux about 6.4x10 12 cm -2 s -1 Total flux about 6.4x10 12 cm -2 s -1 KS n Lab: KS n Lab: KS n Lab: KS KS KS Lab: 28m from core #1 Lab: 28m from core #1 Lab: 28m from core #1 28m from core #1 28m from core #1 28m from core #1 10 m below the surface 10 m 10 m below the surface 10 m below the surface 10 m 10 m below the surface below the surface below the surface 30 30 mwe 30 mwe 30 30 30 mwe mwe overburden mwe overburden mwe overburden overburden overburden overburden 6/36 Studies on Neutrino-Electron Scattering
Neutrino Laboratory Inner Target Volume & Shielding Inner Target Volume & Shielding Inner Target Volume & Shielding 7/36 Studies on Neutrino-Electron Scattering
CsI Scintillating Crystal Array Experimental Approach; Experimental Approach; CsI CsI( (Tl Tl) Crystal ) Crystal Scintillator Scintillator Array Array: proton free target (suppress n e -p background) Normal Event Pulse scale to (tons) design possible Alpha good energy resolution, alpha & gamma Event Pulse Pulse Shape Discrimination (PSD) allows measure energy, position, multiplicity more information for background understanding & suppression DAQ Threshold: 500 keV Analysis Threshold: 3 MeV CsI(Tl) Detector (less ambient background & reactor n e spectra well known) 9x12 Array 200 kg Data Volume: ~ 29883 kg-day / 7369 kg-day Reactor ON/OFF Energy : Total Light Collection E Q Q L R (E) ~ 6% @ E>660 keV Z-position : The variation of Ratio Z Q Q / Q Q (Z) ~ 1.3 cm @ E>660 keV L R L R 8/36 Studies on Neutrino-Electron Scattering
Data Analysis: Event Selection Reactor OFF Reactor OFF Reactor OFF Reactor OFF Reactor OFF Reactor OFF Efficiencies CUTS DAQ Live Time Eff. (3 - 8 MeV) ~ 90% CRV 92.7 % MHV 99.9 % PSD ~100 % Z-pos 80% Total 77.1 % S 1 at 3 MeV B 30 9/36 Studies on Neutrino-Electron Scattering
Background Understanding A. Radioactive Contaminants Decays of radioactive contaminants mainly 232 Th and 238 U decay chain produce background in the region of interest. Estimate the abundance of 137 Cs, 238 U and 232 Th 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 High Energy „s from such as 63 Cu, 208 Tl IDEA: multiple-hit analysis can give us very good understanding 208 Tl, High Energy and cosmic related background in the region of interest. Cosmic & High Energy Gamma Ray - By comparing cosmic and non-cosmic multiple-hit spectra . Tl-208 Decay Cascade - By examining multiple-hit spectra as well as simulation of Tl-208 decay chain energies to understand/suppress background in the region of 3-4 MeV. 10/36 Studies on Neutrino-Electron Scattering
Intrinsic 137 Cs Level Nucl. Instr. and Meth. A 557 (2006) 490-500. 31.3 kg-day of CsI(Tl) data was analysed. 137 Cs contamination level in CsI was derived ==> (1.55 ± 0.02 ) X 10 -17 g/g 11/36 Studies on Neutrino-Electron Scattering
Intrinsic U and Th Contamination Level Data: The total of 40 crystals with data size of 1725 kg·day was analyzed. ii) 212 Bi( b - ,64%) → 212 Po( a , 299ns) → 208 Pb i) 214 Bi( b - )→ 214 Po( a ,164 m s) → 210 Pb Selection: b - pulse followed by a large a pulse Selection: 1 st pulse is b shaped & T 1/2 = ( 283 ± 37 ns. 2 nd pulse a shaped α T 1/2 = (163 ± 8) m s α β β 232 Th abundance = 2.3 ± 0.1 x10 -12 g/g 238 U abundance = 0.82 ± 0.02 x10 -12 g/g T 1/2 = ( 0.141 ± 0.006 s a a iii) 220 Rn a → 216 Po a, 0.15s) → 212 Pb Selection: two a events with time delay less than 1s 232 Th abundance 2.23 ± 0.06 x 10 -12 g/g 12/36 Studies on Neutrino-Electron Scattering
Intrinsic Radiopurity Measurement and Contamination Level 13/36 Studies on Neutrino-Electron Scattering
Estimate the background due to Intrinsic 208 Tl 208 Tl beta with associated gammas 208 Tl beta with associated gammas 232 Th (decay chain) energies deposit in one crystal. energies deposit in one crystal. 3a, 3b BR 36% 0.4% 0.00134 This is 11% of signal and can be negligible in our background level of ~ 0.4 cpd in 3 - 5 MeV 14/36 Studies on Neutrino-Electron Scattering
Background Understanding: via Multiple Hit Analysis 2 HIT SPECTRUM 3-4 3-4 4 MeV 4 MeV MeV MeV 4-8 4-8 8 MeV 8 MeV MeV MeV 15/36 Studies on Neutrino-Electron Scattering
Background Understanding via Multi Hit E tot = 1-2 MeV E tot = 2-3 MeV 511 keV External Source(s) 605 keV 2100 keV 796 keV 1173 keV 1332 keV • Co-60: 1173.2 keV 99.86% accompanied with 1332.5 keV 99.98% • The background related to reactor. Mostly come from the dust. • Tl Pair Production: One escape peaks • (~ 2105 + 511 keV) Cs-134 (n + 133 Cs g 134 Cs) E tot = 3-4 MeV External Source(s) 510, 583 keV • 605 keV 97.6%; • 796 keV 85.5% 2614 keV With the Q of beta decay at 2MeV Internal Source(s) 2614 keV 99 % accompanied with 583 keV 85% 860 keV 510.8 keV 23% 860 keV with 13% Cosmic induced neutrons can be Combination of Tl gammas can affect up to around 4 MeV captured by the target nuclei 133 Cs. 16/36 Studies on Neutrino-Electron Scattering
Background Prediction via PAIR PRODUCTION q 2 - HIT 3 - HIT p E e-e+ E e-e+ q q p E e-e+ SH p 17/36 Studies on Neutrino-Electron Scattering
Residual Background Understanding & Suppression Background Sources : High Energy -rays & Cosmic Rays & 208 Tl Idea -- Use Multiple Crystal Hit ( MH) spectra to predict Idea -- Use Multiple Crystal Hit ( MH) spectra to predict Idea -- Use Multiple Crystal Hit ( MH) spectra to predict Single Crystal Hit ( SH ) Background to the neutrino events Single Crystal Hit ( SH ) Background to the neutrino events Single Crystal Hit ( SH ) Background to the neutrino events MH non SH [ BKG (cos)] cos ( ) 1 ( ) ON , OFF ON , OFF MH SH tot tot SH [ BKG ( 2614 583 )] SH [ 2614 583 ( MC )] MH [ 2614 ; 583 ( data )] MH [ 2614 ; 583 ( MC )] 18/36 Studies on Neutrino-Electron Scattering
Background Understanding & Suppression Combined BKG(SH) from three measurements : Direct Reactor OFF(SH) spectra Predicted BKG(SH) from OFF(MH) Predicted BKG(SH) from ON(MH) n = ON(SH) – BKG(SH) 19/36 Studies on Neutrino-Electron Scattering
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