1 Performance and Physics with the CsI(Tl) Array at the Kuo-Sheng Reactor Neutrino Laboratory  Physics with CsI(Tl) detector  Period -2 configuration  Data analysis ※ Cuts ※ Cut summary (central crystals)  Results (Prilim.)  Background  Status and plans  Summary V. Singh (On behalf of the TEXONO Collaboration) IoP, Academia Sinica, Taipei, Taiwan

2 Physics with CsI(Tl) detcetor physics full of surprises, need intense -source Reactor : high flux of low (MeV range) energy electron anti- neutrinos e + p e + + n Reactor -spectrum has been measured (~2% in the MeV) For ( e -e), both NC & CC and their interference term contribute g

3 Physics with CsI(Tl) detcetor Investigations of ( e -e) cross-sections with reactor s To study : Electro-weak parameters (g v, g A, Sin 2  W ) at the MeV range CC & NC interference anomalous magnetic moments and mean square charge radius NCEX on nuclei by e + (A,Z) e + (A,Z)* NOT observed at lower energies ! CsI(Tl) have good  resolution and capture efficiency & suitable to study these processes.

4 KS Expt. : Period II Configuration Shielding & Veto [one side] Period II : Jan.28, 2003 – Jan ( ~ 50 days OFF) CsI(Tl) Array (186 kg)

5 KS Expt: Period II CsI(Tl) Detector CsI(Tl) [ 186 kg ] Connecting Board Multi-Disks Array [800 Gb] Flash ADC Readout [16 ch, 20 MHz, 8 bit]

6 Reactor Neutrino Interaction Cross-Sections P3+: Coh. ( N) < 1 keV P1: MM ( e) keV P2: SM ( e) > 2 MeV

7 KS/P-2/CsI(Tl)/Cross-Section Data  Data Volume:  Total more than 250 / 50 days ON/OFF  CsI(Tl) Performance:  186 kg mass (Future target 500 kg mass)  FWHM energy resolution of 660 keV Z-position resolution is 660 keV  Range of O( cpd) [counts kg -1 day -1 10keV -1 3 MeV background  Analysis:  Cosmic Veto (5  s gate)  Anti-Compton (Whole Ge detector assembly + Rest CsI(Tl) crystals)  Pulse Shape Disc. (Alphas, elect. noise, accidentals etc.)

CsI(Tl) crystal layout Plastic20+20 cm40 cm7 central cry.Anal. underway

9 Period-2 CsI(Tl) Array : 186 kg, 93 crystals Single Crystal Q L Vs Q R (Raw Data) Region of Interest for SM  e) Z = 0 cm Z =40 cm 208Tl 40K 137Cs

10 Data Analysis Techniques Defining Cuts: 1] General Cuts – a) No Cut energy spectrum b) Single Event Hit & Single Crystal Hit c) Cosmic ray Cut SEH, & SCH SEH, SCH, & Cosmic SEH, SCH SEH, SCH, Cosmic-ray, & Z-pos SEH, SCH No Cut: Energy Spectrum

11 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 Data Analysis Techniques A;. Alpha Event Pulse Normal Event Pulse

12 Defining Cuts: 3] Special Cuts – b) Very narrow Event Cut (Very fast decay time) Select- event having partial charge less than 3 Note- Not in all crystals. Data Analysis Techniques

13 Data Analysis Techniques Defining Cuts: 4] Special Cuts – c) Double Pulse Cut Select – Event having Larger Time Avg. but low charge ! A; Right side Double Pulse

14 Data Analysis Techniques Defining Cuts: 5] Z-position Cut – Select – Both side peak mean initially taken as 0 & 40 ! 40cm long crystal No cut Narrow Pulse Alpha Pulse Normal Pulse 0 cm 40 cm

15 Cut Summary of Central Crystals Cut type Over all energy Above 3 MeV (%)(%) [1] Cosmic ray1188 [2] anti-Comp.7086 [3] Single Tri.0102 [4] [5] Alpha+Narrow 1083 [6] Double Pulse 1138 [7] PSD 2595 [8] All Cuts 3296 * Z-position cut is not applied !!

16 Period-2 CsI(Tl) Array : Results (prilim.) Energy Spectrum of Alpha and narrow pulse Narrow Pulse Peak Alpha Peaks Z-positon of Alpha

kg-days Energy Spectrum of recoil electron * 16 Central Crystals * Mass 32 kg * Data set 6.9 days OFF period Period-2 CsI(Tl) Array : Results (Prilim.) 137Cs (661 keV) 40K (1461 keV) 208Tl (2615 keV)

18 Period-2 CsI(Tl) Array : Results (Prilim.) The Estimate of BKG Suppression >3 MeV * Cosmic ~ one order * From Veto to All Cuts > Two order * 100kg All Cuts to ON-OFF ~ One order * S/B ratio (integral > 3 MeV) = 1/10 Differential Event Count for CsI(Tl)

19 BKG in CsI(Tl) detcetor Internal intrinsic radioactivity: Multi-structure in Alpha spectrum (study is underway) Concentration of 137 Cs = 1/   ( 2.14 x ) g / g *  is more than 0.5

20 Attempt measurement of Standard Model  ( e e - )  sin   w at MeV range Analysis: [1]  Central 16 crystals gone well To study alpha spectrum Need more attention a) Energy resolution b) Z-position  Rest 15 (40cm) is next step  Rest 10 (40cm) and 17 (20cm) is second next step Future Upgrades and Modifications of the Expt.:  Goal of achieving a 500 kg system  Improvements of Shielding  More Physics Data Taking To investigate complementary detection technique To study the other unexplored channels Status and Plans

21 Present Results: Bkg ~ kg -1 day keV -1 at 3 MeV ON - OFF ~ kg -1 day -1 10keV -1 at 3 MeV S/B ratio = 1/10 Summary After analyzing all crystals and after ON - OFF Data, we will present better results ! Thanking you for your kind attention !

22 Cut Summary of Central Crystals [01]= Cry. #, [02]= Cosmic, [03]= Single Cry., [04]= Single Tri., [05]=Cos+Sc+St, [06]= Alpha+Narrow, [07]= Wrong ipos, [08]= Double Pulse, [9]= PSD, [10]= All cuts

23 Cut Summary of Central Crystals ( > 3 MeV) [01]= Cry. #, [02]= Cosmic, [03]= Single Cry., [04]= Single Tri., [05]=Cos+Sc+St, [06]= Alpha+Narrow, [07]= Wrong ipos, [08]= Double Pulse, [9]= PSD, [10]= All cuts