Measurement of Neutrino-Electron Scattering with CsI(Tl) Scintillators at the Kuo-Sheng Neutrino Laboratory Academia Sinica Seminar Taipei, TAIWAN, 21 May 2010 Muhammed Deniz 1,2 1: IoP, Academia Sinica, Taiwan 2: METU, Ankara, Turkey On behalf of TEXONO Collaboration

Theory overview e – e - Scattering – Motivation Theory overview e – e - Scattering – Motivation Cross Section & EW Parameters – World Status Cross Section & EW Parameters – World Status TEXONO Physics Program TEXONO Physics Program TEXONO Experiment – CsI(Tl) Array TEXONO Experiment – CsI(Tl) Array  Event Selection & Data Analysis Outline  Background Understanding & Suppression  Analysis Results Probing New Physics – NSI & UP with e – e - Probing New Physics – NSI & UP with e – e - Summary Summary 2/43 Measurement of Neutrino-Electron Scattering

e – e - Scattering Formalism e + e - e + e - A basic SM process with CC, NC & Interference Not well-studied in reactor energy range ~ MeV Measurement of Neutrino-Electron Scattering 3/43

e + e - e + e - Neutrino-Electron Scattering Cross-Section Measurement of Neutrino-Electron Scattering 4/43

Characteristics of the previous antineutrino-e scattering experiments CsI(Tl) Scin ~ % CF4 gas %Si(Li) %Fluorocarbon ….0.153% Plastic Scin %* TEXONOMUNURovnoKrasnoyarskSavannahExperimentsExperiments Target Fiducial Mass (kg) Thr. (MeV) Signal Events S / B Accuracy  ( e e) Target Fiducial Mass (kg) Thr. (MeV) Signal Events S / B Accuracy  ( e e) World Status Characteristics of the previous neutrino-e scattering Accelerator experiments Plastic Scin. 15 tons 15 tons % Liquid Scin. 167 tons 167 tons % LAMPFLSNDExperimentsExperiments Target Fiducial Mass Thr. (MeV) Signal Events Accuracy  ( e e) Target Fiducial Mass Thr. (MeV) Signal Events Accuracy  ( e e) Measurement of Neutrino-Electron Scattering 5/43

sin 2  W measurement in the World “There is NO significant measurement at low energies especially with reactor anti-neutrino” PDG 2008 ? Measurement of Neutrino-Electron Scattering 6/43

TEXONO Physics Program TEXONO Collaboration: Taiwan (AS,INER,KSNPS,NTU); China (IHEP,CIAE,THU,NKU,SCU,LNU); Turkey (METU); India (BHU) Program: Low Energy Neutrino & Astroparticle Physics [1] Magnetic Moment Search at ~10 keV  PRL 2003, PRD 2007 [2] Cross-Section and EW Parameters measurement at MeV range  PRD 2010 [3] e N Coherent Scattering & WIMP Search at sub keV range Taiwan EXperiment On NeutrinO massquality Detector requirements [3] [2] [1] Measurement of Neutrino-Electron Scattering 7/43

TEXONO Physics Program on CsI(Tl) detector attempt a measurement of Standard Model  e e    sin 2  w at MeV range Measurement : Recoil Energy of e  attempt a measurement of Standard Model  e e    sin 2  w at MeV range Measurement : Recoil Energy of e  e + e - e + e - Reactor : high flux of low energy (MeV range) electron anti-neutrinos.   properties are not fully understood intense -source Region of Interest for e - e scattering Big uncertainties of modeling in the low energy part of reactor neutrino for SM  ( e e) higher energies (T>3 MeV) Region of Interest for e - e scattering Big uncertainties of modeling in the low energy part of reactor neutrino for SM  ( e e) higher energies (T>3 MeV) CsI(Tl) (200 kg) : Measurement of Neutrino-Electron Scattering 8/43

Kou-Sheng Reactor Power Plant Measurement of Neutrino-Electron Scattering 9/43

Neutrino Laboratory Measurement of Neutrino-Electron Scattering 10/43

Alpha Event Pulse Normal Event Pulse CsI Scintillating Crystal Array CsI(Tl) Detector 9x12 Array 200 kg Experimental Approach; CsI(Tl) Crystal Scintillator Array Experimental Approach; CsI(Tl) Crystal Scintillator Array: proton free target (suppress e -p background) scale to  (tons) design possible good energy resolution, alpha & gamma Pulse Shape Discrimination (PSD) allows measure energy, position, multiplicity more information for  background understanding & suppression Energy : Total Light Collection  (E) ~ 10% E>660 keV Z-position : The variation of Ratio  (Z) ~ 1.3 E>660 keV  DAQ Threshold: 500 keV  Analysis Threshold: 3 MeV (less ambient background & reactor e spectra well known)  Data Volume: ~ kg-day / 7369 kg-day ON/OFF Measurement of Neutrino-Electron Scattering 11/43

KS CsI(Tl) Experiment Configuration Multi-Disks Array (several Tb) CsI(Tl) (200 kg)Connecting Board FADC Readout 16 ch., 20 MHz, 8 bit Measurement of Neutrino-Electron Scattering 12/43

Dynamic Range of FADC Unsaturated Saturated Goal: to reconstruct the missing part of the saturated pulse to get the charge and energy. Single Crystal Q L vs Q R (Raw Data) Region of Interest for SM  e e) Z = 0 cm 208 Tl 40 K 137 Cs QLQL QRQR Z =40 cm Nucl. Instr. and Meth. A 511 (2003) Measurement of Neutrino-Electron Scattering 13/43

Data Analysis: Event Selection CUTS (3 - 8 MeV) Efficiencies DAQ Live Time Eff. ~ 90% CRV 92.7 % MHV 99.9 % PSD ~100 % Z-pos 80% Total 77.1 % Measurement of Neutrino-Electron Scattering 14/43

 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. A. Radioactive Contaminants Background Understanding  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 - By comparing cosmic and non-cosmic multiple-hit spectra.  Tl 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. B. Environmental Backgrounds Measurement of Neutrino-Electron Scattering 15/43

Intrinsic 137 Cs Level 137 Cs contamination level in CsI was drived ==> (1.55 ± 0.02 ) X g/g 31.3 kg-day of CsI(Tl) data was analysed. Nucl. Instr. and Meth. A 557 (2006) Measurement of Neutrino-Electron Scattering 16/43

β α Data: The total of 40 crystals with data size of 1725 kg·day was analyzed. i) 214 Bi(  - )→ 214 Po( ,164  s) → 210 Pb Intrinsic U and Th Contamination Level T 1/2 = (163 ±8)  s 238 U abundance = 0.82 ± 0.02 x g/g iii) 220 Rn  → 216 Po  0.15s) → 212 Pb   T 1/2 = (  ±  s 232 Th abundance  2.23 ± 0.06 x g/g ii) 212 Bi(  -,64%) → 212 Po( , 299ns) → 208 Pb Selection:  - pulse followed by a large  pulse Selection: 1 st pulse is  shaped & 2 nd pulse  shaped Selection: two  events with time delay less than 1s T 1/2 = (  ± 37  ns. 232 Th abundance = 2.3 ± 0.1 x g/g β α Measurement of Neutrino-Electron Scattering 17/43

Intrinsic Radiopurity Measurement and Contamination Level Measurement of Neutrino-Electron Scattering 18/43

BR 36% This is 11% of signal and can be negligible in our background level of ~ 0.4 cpd in MeV 208 Tl beta with associated gammas energies deposit in one crystal. 208 Tl beta with associated gammas energies deposit in one crystal. Estimate the background due to Intrinsic 208 Tl 232 Th (decay chain) 3a, 3b 0.4% Measurement of Neutrino-Electron Scattering 19/43

Background Understanding: via Multiple Hit Analysis 2 HIT SPECTRUM 3-4 MeV 4-8 MeV Measurement of Neutrino-Electron Scattering 20/43

Background Understanding via Multi Hit 511 keV 1173 keV1332 keV 2100 keV External Source(s) Co-60: keV 99.86% accompanied with keV 99.98% The background related to reactor. Mostly come from the dust. Tl Pair Production: One escape peaks (~ keV) Internal Source(s)  Cosmic induced neutrons can be captured by the target nuclei 133 Cs. Cs-134 (n Cs  134 Cs) 605 keV 97.6%; 796 keV 85.5% With the Q of beta decay at 2MeV  Combination of Tl gammas can affect up to around 4 MeV External Source(s) 2614 keV 99 % accompanied with 583 keV 85% keV 23% 860 keV with 13% 510, 583 keV 860 keV 2614 keV 605 keV 796 keV E tot = 1-2 MeVE tot = 2-3 MeVE tot = 3-4 MeV Measurement of Neutrino-Electron Scattering 21/43

E e-e+ Background Prediction via PAIR PRODUCTION 3 - HIT2 - HIT SHSH p q p p q q Measurement of Neutrino-Electron Scattering 22/43

Environmental Background Understanding Tl-208 (3-4 MeV) 208 Tl chain 2-hit energy spectra Simulation with angular correlation cosmic/non-cosmic ratio for 3-hit Pair production events Cosmic Inefficiency All crystals including and 40 cm crystals data was analyzed. Measurement of Neutrino-Electron Scattering 23/43

Residual Background Understanding & Suppression Background Sources : High Energy  & Cosmic Rays & 208 Tl Measurement of Neutrino-Electron Scattering 24/43

Background Understanding: Due to Tl-208 in 3-4 MeV Region Measurement of Neutrino-Electron Scattering 25/43

Tl-208 Induced and Cosmic SH BKG Estimation SH  2614 keV   (583 keV  ) or  (510 keV  ) or  (860 keV  )  Measurement of Neutrino-Electron Scattering 26/43 OFF-BKG

Background Understanding & Suppression Measurement of Neutrino-Electron Scattering 27/43 Combined BKG(SH) from three measurements: Direct Reactor OFF(SH) spectra  Predicted BKG(SH) from OFF(MH)  Predicted BKG(SH) from ON(MH)  = ON(SH) – BKG(SH) Combined BKG(SH) from three measurements: Direct Reactor OFF(SH) spectra  Predicted BKG(SH) from OFF(MH)  Predicted BKG(SH) from ON(MH)  = ON(SH) – BKG(SH)

BKG – Pred. (neutrino free region) Systematic Uncertainties Approach – Use non- events for demonstration ON-OFF Stability < ~0.5% Random trigger events for DAQ & Selection Cuts Stability of Tl-208 (2614 keV) peak events Cosmic Induced BKG(SH) Prediction < ~1 % Successfully Predict Cosmic BKG in NEUTRINO FREE REGION Tl-208 Induced BKG(SH) Prediction <~3% Successfully Predict Tl-208 Induced BKG(SH) >3MeV at Reactor OFF periods Successfully Predict Tl-208 peak intensity for both Reactor ON/OFF with the same tools (MC) 208 Tl (SH) Prediction 208 Tl Peak Events Stability Measurement of Neutrino-Electron Scattering 28/43

The Sources & Contribution of Systematic Uncertainties Measurement of Neutrino-Electron Scattering 29/43

Cross Section & Weak Mixing Angle ON-BKG Phys. Rev. D 81, (2010) Measurement of Neutrino-Electron Scattering 30/43 A Better Sensitivity

World Status: Summary Table e  e - Energy (MeV)Events – – – 4.5 N/A 3.15 – 5.18N/A Experiment LAMPF [Liquid Scin.] LSND [Liquid Scin.] Savannah-River [Plastic Scin.] Savannah-River Re-analysed (PRD1989, Engel&Vogel) Krasnoyarsk (Fluorocarbon) Cross-Section sin 2  W [10.0 ± 1.5 ± 0.9] x E e cm ± [10.1 ± 1.1 ± 1.0] x E e cm ± [0.86 ± 0.25] x  V-A [1.70 ± 0.44] x  V-A 0.29 ± 0.05 N/A [4.5 ± 2.4] x cm 2 /fission 0.22 ± – Rovno [Si(Li)] [1.26 ± 0.62] x cm 2 /fission N/A 0.7 – MUNU [CF 4 (gas)] 1.07 ± 0.34 events day -1 N/A ± 80 ± 61 TEXONO [CsI(Tl) Scin.] [1.08 ± 0.21 ± 0.16] x R SM ± 0.031(stat) ± 0.024(sys) [1.35 ± 0.4] x  SM [2.0 ± 0.5] x  SM Measurement of Neutrino-Electron Scattering 31/43

Neutrino-Electron Scattering Cross-Section e + e - e + e - Measurement of Neutrino-Electron Scattering 32/43

Interference, Neutrino Magnetic Moment and Charge Radius at 90 % C. L.  2 = [0.42 ± 1.79(stat) ± 1.49(sys)].  B 2 Interference Term  = ± 0.30(stat) ± 0.24(sys) Interference Term  = ± 0.30(stat) ± 0.24(sys) Measurement of Neutrino-Electron Scattering 33/43

 The main parameters will be for FC NSI and for NU-NSI.  There is a strict bound on derived from  e decay NSI of Neutrino Measurement of Neutrino-Electron Scattering 34/43 ─ V-A Form, similar to the four Fermi  exchange of Higgs  Supersymmetric scalar bosons  New heavy gauge boson Z’ ─  mass models all mechanisms carry modifications to the structure of the standard EW NC& CC

NSI of Neutrino Measurement of Neutrino-Electron Scattering 35/43 e – e - scattering provide a sensitive tool to probe NSI ─ e – e - scattering provide a sensitive tool to probe NSI

Comparison of Bounds of NSI Parameters Measurement of Neutrino-Electron Scattering 36/43

1.Exchange of Scalar Unparticles i = 0(1) : Unparticle scalar/vector field     : Scalar(Vector) unparticle couplings f : e, u, d  denotes neutrino flavours d: Unparticle mass dimension  : Unparticle energy scale Unparticles 2. Exchange of Vector Unparticles For the flavour changing case: For the flavour conserving case Measurement of Neutrino-Electron Scattering 37/43  The notion of unparticles is introduced by Howard Georgi. A scale invariant sector which decouples at a suffciently large energy scale exists. (Phys. Rev. Lett. 98, (2007)  The signatures of Unparticle Physics can also be observed by reactor neutrinos by searching the effects of virtual unparticle exchange between fermionic currents.  This interaction can be either exchange of Scalar Unparticles or Vector Unparticles.

Unparticle physics is a speculative theory that conjectures matter that can not be explained in terms of particles, because its components are “scale invariant”, a property of fractals. A fractal is a rough or fragmented geometric shape that can be split into parts, each of which is (at least approximately) a reduced-size copy of the whole," a property called self-similarity. “Scale invariance” is a feature of objects or laws that do not change if length scales (or energy scales) are multiplied by a common factor. Unparticle Physics Measurement of Neutrino-Electron Scattering 38/43

Unparticles Measurement of Neutrino-Electron Scattering 39/43  + e - UP  + e -

Unparticle – Exclusion Plots Measurement of Neutrino-Electron Scattering 40/43

Scalar Unparticle – Preliminary Results Measurement of Neutrino-Electron Scattering 41/43 Results are improved over those from Borexino and MUNU experiments Unparticle effects decreases as  U increases

Vector Unparticle – Preliminary Results Measurement of Neutrino-Electron Scattering 42/43

Summary Detector: CsI(Tl) Scintillating Crystal Array (~ 200 kg) Threshold: 3 MeV Analysis Results:  ( e – e - ) with ~ 25% accuracy Weak Mixing Angle with ~ 15% accuracy Verify SM negative interference  sensitivity ~  B neutrino charge radius sensitivity ~ cm 2 Probing new Physics : NSI and UP -- Preliminary Current bounds are improved over those from the previous experiments Measurement of Neutrino-Electron Scattering 43/43

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