Research Program of TEXONO : Status and First Results TEXONO Collaboration : Overview Kuo-Sheng(國聖) Reactor Neutrino Lab. ※ First Results with ULB-HPGe R&D Projects Status and Plans Henry T. Wong / 王子敬 Academia Sinica / 中央研究院 @ Matsushima, Sendai / 仙台 松島 March 02

TEXONO* Collaboration W.C. Chang¶, C.P. Chen, K.C. Cheng, H.C. Hsu, F.S. Lee, S.C. Lee, S.T. Lin, D.S. Su, P.K. Teng, W.S. Tse¶, H.T.K. Wong†, C.S. Wu, S.C. Wu Academia Sinica, Taipei, Taiwan W.P. Lai Chung Kuo Institute of Technology, Taipei, Taiwan C.H. Hu, J.M. Huang, W.S. Kuo, T.R. Yeh Institute of Nuclear Energy Research, Lungtan, Taiwan H.B. Li, C.H. Tang, M.Z. Wang¶ National Taiwan University, Taipei, Taiwan J.H. Chao, J.H. Liang National Tsing Hua University, Hsinchu, Taiwan Z.M. Fang, R.F. Su Nuclear Power Station II, Kuosheng, Taiwan M. He, S. Jiang, L. Hou, H.Q. Tang, B. Xin, Z.Y. Zhou¶ Institute of Atomic Energy, Beijing, China J. Li†, Y. Liu, Z.P. Mao, J. Nie, J.F. Qiu, H.Y. Sheng, P.L. Wang, X.W. Wang, Q. Yue, D.X. Zhao, J.W. Zhao, P.P. Zhao, S.Q. Zhao, B.A. Zhuang Institute of High Energy Physics, Beijing, China Z.S. Liu, Z.Y. Zhang Institute of Radiation Protection, Taiyuan, China T.Y. Chen Nanjing University, Nanjing, China J.P. Cheng Tsing Hua University, Beijing, China C.Y. Chang, G.C.C. Chang† University of Maryland, Maryland, U.S.A. † Co-Prinicipal Investigators ¶ Project Leaders Ph.D. Students HISTORY Initiate : Chang Chung-Yung 1996 First ICollaboration Meeting/Official Start : October 1997 First Paper : October 1998 KS Reactor Experiment Installation : June 2000 First Ph.D. : Liu Yan , July 2000 First Physics Data Taking : June 2001. *Taiwan EXperiement On NeutrinO Home Page @ http://hepmail.phys.sinica.edu.tw/~texono/

TEXONO Overview Goals : Program : Neutrino and Astroparticle Physics  Starting phase: 1st particle physics expt in Taiwan Build up a Qualified Group  1st big research Coll. % Taiwan & China Program : Kuo-Sheng Reactor Neutrino Lab. ※ mn0  anomalous n properties & interactions ※ n’s strange & full of surprises  study new regime wherever possible experimentally R&D Projects  diversified program ※ reactor program as base ※ explore various future scenarios0

Kuo-Sheng Nuclear Power Plant KS NPS-II : 2 cores X 2.9 GW KS n Lab: 28 m from core#1

Kuo-Sheng Neutrino Laboratory High flux of ne (also ….. ne ) Modular Design  independent detector, electronics, shielding high-Z target, large re Improved detector performance:  good energy & spatial resolution,  low threshold, a/g separation Elaborate electronics+DAQ+control sys.  complete record of pulse shape + timing info. Elaborate Shieldings  radon purge & 4p cosmic veto Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics

Kuo Sheng Reactor Neutrino Laboratory Front Gate Front View (cosmic vetos, shieldings, control room …..) Inner Target Volume

ULB-HPGe + Anti-Comptons KS Expt. : Period I Configuration Period I : June 01 – March 02 (60 days OFF) Shielding & Veto [one side] ULB-HPGe + Anti-Comptons CsI(Tl) Array

KS Expt: Period I Detectors ULB-HPGe [1 kg] CsI(Tl) [46 kg] FADC Readout [16 ch., 20 MHz, 8 bit] Multi-Disks Array [600 Gb]

mn with Reactor ne mn: Experimental Probe:  parametrize possible niL njR + g vertices   both i = j “diagonal” & i  j “transition” moments Experimental Probe:  Study ne + e-  nX + e-  Focus on low recoil energy ※ sm  T–1 ※ decouples SM “background” [ ……… LE reactor f(ne) not accurately known]  Look for Excess in Reactor ON/OFF Neutrino Radiative Decay (Gn):  sm & Gn related  same vertices – real g for Gn Electron Recoil Spectra

KS/P1/Ge/mn Data Data Volume: HPGe Performance: Analysis:  Expected total 200/60 days ON/OFF [ reported here : 62/46 ON/OFF ] HPGe Performance:  1.06 kg mass  0.4 keV RMS @ 10 keV  5 keV threshold [Unique Data]  Range of O(1 cpd) [counts kg-1 day-1 keV-1] background c/f Dark Matter expt. Analysis:  Cosmic Veto (5 ms gate)  Anti-Compton (Well+Base detectors)  Pulse Shape Disc. (veto elect. noise)  Timing Analysis (veto clusters) [not yet implemented here] Efficiencies Normalization:  DAQ book-keeping  Monitor random triggers  Monitor residual 40K peaks  Monitor 10 keV Ga X-rays peak

Cosmic Veto : Timing Plot evidence of delayed induced neutron activities choose Dt=5 ms HPGe Vs NaI(Tl) : 2D Plot Necessary Cross Checks observed : ※ full capture peaks, Compton edges, coincidences …. etc

KS/P1/Ge : Spectra & Residual Based on 62/46 days of Reactor ON/OFF data

KS/P1/Ge : First Results Residual Plot Fit OFF spectra to fOFF E/keV fOFF c2/dof 12-61 a1e-a2E+a3+a4E 39/46 Fit ON spectra to fOFF + fSM + mn2 fMM [10-10 mB] Best Fit : mn2 = -1.7  2.5 @ c2/dof = 55/49 [Comparable sensitivities to direct-search world limits] Improvements Expected :  more data [ 3+ ON]  complete & improved analysis  treatment of threshold region [e.g. timing] [Aim : ~ 5 keV]

Reactor mn(ne) Sensitivities Gn Sensitivities

KS/P1 Analysis HPGe : exploit the low threshold data Established Problem: mn and Gn for ne via ne + e  nx + e Speculative Analysis: ※ study ne flux from reactor  due to neutron excitation producing e.g. 51Cr, 55Fe [distinct energy & timing …..]  study mn & Gn for ne ※ anomalous Neutrino Interactions in Matter e.g. anomalous energy deposition X (>eV) ne + N  nx + N + X [similar analysis as accelerator nm] ※ study possible nuclear transitions e.g. 73Ge* decays by 2g’s separated by t1/2=4.6 ms CsI(Tl) : Technical Run Event Reconstruction Background Studies Optimize for P2

Tagging of 73Ge ½- 2g transitions: Event-by-Event background-free tag with PSD To do : Reactor ON/OFF analysis on the system ~1 s before the transition

CsI(Tl) Array : Highlights 40 cm length (longest commercial prod.) Energy+3D info:  10% FWHM at 660 keV  s(z) <2 cm @ E>250 keV Detector Threshold ~ 20 keV PSD for g/a : > 99% Intrinsic Purity :  238U/232Th < 10-12 g/g (equil.)  40K < 10-10 g/g cosmic muon events on-site @ 46 kg target Goals: Commission 150+ kg target on-site for Period-II DAQ with large dynamic range

KS Expt.: Future Thoughts Existing configurations:  push mn/Gn sensitivities  s(ne–e) scatterings  analysis opened up by low threshold Push threshold lower ( X 1/10 )  coherent nN scattering Insert passive targets for s(nucl.) e.g. 6Li, 7Li, 10B, 11B, 2H ….. As base to launch other projects  explored by R&D program

R&D Projects Upgrading FADCs Trace Radio-purity with AMS Explore New Detectors Scenarios  loaded crystal scintillator  ultra low energy HPGe CsI(Tl) for Dark Matter Searches Upgrading FADCs Trace Radio-purity with AMS ( Accelerator Mass Spectrometry) Close Contact with :  CsI(Tl) CDM search @ Korea  JHFBeijing LBL n project @ IHEP  Ultra HE (1015 eV) n Telescope @ NTU

CsI(Tl) for CDM Searches Potential Merits: Better PSD for g/a separation than NaI(Tl) Minimal passive materials Large target mass possible (c/f em-calorimeters 40 tons) Highlights of R&D Program: Quenching Factor measurements with neutron beam  lowest threshold data 1st direct measurement of diff. cross section in heavy nuclei PSD studies with Neural Net.  improve conventional methods N KIMS Expt. (apprd.) :  200 kg CsI(Tl) for CDM in S. Korea

Upgrade FADC 40 MHz ; 12 bit ; 32 ch/module @ 9 U VME [ c/f KS FADC : 20 MHz ; 8 bit ; 16 ch/module ] On-board processing with FPGA 1000 channels to be used in TPC in LEPS Expt. @ SPring8 by Fall 2002. TPC for LEPS @ SPring8 Prototype Measurements :

Trace Radio-purity with AMS Based at AMS facilities @CIAE with 13 MV Tandem Potential Merits:  small samples, quick  versatile on sample choice  sensitive to a/b emitters  sensitive to stable isotope & extrapolate (e.g. 39K)  >103 improvements over ICP-MS [ …….. once prescriptions are known. ] Status :  demonstrate 129I/127I < 10-12 g/g  measure 40K~10-10 g/g in CsI (powder) Sensitivity goal : 10-14 g/g Future :  different bases e.g. liquid scintillator  87Rb …… [238U / 232Th series after Tandem upgrade]

Summary TEXONO Collaboration:  Built-Up and Growing Kuo-Sheng Neutrino Lab.:  Established & Operational ※Modular & Flexible Design  Physics Data Taking since June 01 ※Unique HPGe Low Energy Data ※ Bkg Level ~ Udrgd. CDM Expt. Expect Results on mn (Gn) soon Preparation of Period-II DAQ  Improved HPGe Conf.  Commissioning 150+ kg CsI(Tl) [Welcome Ideas/Suggestions on Possibilities Beyond] Diversified R&D Program in parallel