Recent Result and Status of TEXONO Experiments V. Singh (On behalf of the TEXONO Collaboration) IoP, Academia Sinica, Taipei, Taiwan TEXONO Collaboration : Overview Kuo-Sheng(國聖) Reactor Neutrino Lab. ※ Magnetic Moments Results with ULB-HPGe ※ Other topics being pursued/in preparation R&D Program

Program: Pioneering Efforts : TEXONO Overview Kuo-Sheng Reactor Neutrino Laboratory ※ reactor : high flux of low energy electron anti-neutrinos ※ mn0  anomalous n properties & interactions ※ n physics full of surprises , need intense n-source  study/constraint new regime wherever possible experimentally  explore possible new detection channels R&D Projects Pioneering Efforts : KS Expt: 1st particle physics experiment in Taiwan TEXONO Coll. : 1st big research Coll. % Taiwan & China [feature report in Science, Vol. 300, 1074 (2003) ]

Kuo-Sheng Nuclear Power Plant KS NPS-II : 2 cores  2.9 GW KS n Lab: 28 m from core#1 Powerful collaboration: Scientists from Taiwan and mainland China are studying neutrinos from this nuclear power plant outside Taipei.

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

KS Expt. : Period I Configuration Period I : June 2001 – April 2002 (60 days OFF) Shielding & Veto [one side] ULB-HPGe + Anti-Comptons CsI(Tl) Array (46 kg)

KS Expt: Period I Detectors ULB-HPGe [1 kg] CsI(Tl) [46 kg] FADC Readout [16 ch., 20 MHz, 8 bit] Multi-Disks Array [800 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:  Total 4712/1250 hours ON/OFF (No residual observed) HPGe Performance:  1.06 kg mass  0.4 keV RMS @ 10 keV  5 keV detector 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, accidentals) Efficiencies Normalization: (to <0.2%)  DAQ book-keeping  Monitor random triggers  Monitor residual 40K peaks  Monitor 10 keV Ga X-rays peak

KS/P1/Ge/mn : Results Fit OFF spectra to p5 Measure [fOFF;dfOFF ] (@ c2/dof = 80/96 ) Fit ON spectra to fOFF + fSM + k2 fMM [10-10 mB] Fit Results (@ c2/dof = 48/49 ): k2 = -0.4  1.3 (stat.)  0.4 (sys.) Limits derived : mn < 1.3 (1.0)  10-10 mB @ 90(68)% C.L. H.B. Li et al., TEXONO Coll., Phys. Rev. Lett. 90, 131802 (2003)

Reactor mn(ne) Sensitivities Gn Sensitivities

Prototype ULE-HPGe [5 g] : Status & Plans HPGe [1 kg] : mn + Gn : x2 more data improved background & analysis study ne flux from reactor dominated by 51Cr : ~ 10-3 (prelim.) study possible neutrino induced nuclear transitions e.g. 73Ge* decays by 2g’s separated by t1/2=4.6 ms CsI(Tl) [186 kg] : attempt measurement of Standard Model s(nee-)  sin2qw at MeV range Prototype ULE-HPGe [5 g] : threshold < 300 eV  ~ 100 eV explore potentials on nN coherent scattering & CDM

Reactor Neutrino Interaction Cross-Sections P2: SM (ne) > 2 MeV P3+: Coh. (nN) < 1 keV P1: MM (ne) 1-100 keV

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 To look for : possible n-induced nuclear transitions

Period-2 CsI(Tl) Array : 186 kg, 93 crystals Single Crystal QL Vs QR (Raw Data) Z = 0 cm Z =40 cm 208Tl 40K 137Cs Region of Interest for SM s(ne)

Data Analysis Techniques No Cut: Energy Spectrum Defining Cuts: 1] General Cuts – a) No Cut energy spectrum b) 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

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

Data Analysis Techniques Defining Cuts: 2] Special Cuts – c) Right side Double Pulse Cut Select – Event having Larger Time Avg. but low charge ! A; Right side Double Pulse

Period-2 CsI(Tl) Array : 186 kg, 93 crystals Energy Spectrum of recoil electron 137Cs (661 keV) 40K (1461 keV) 208Tl (2615 keV) 2.9 MeV * Central Crystal * Mass 2 kg * Data set 6.7 days OFF period

Period-2 CsI(Tl) Array : 186 kg, 93 crystals Integrated Event Count for CsI(Tl) * Above 3 Mev 0.166 counts/day/kg * Signal to background ration 0.063 i.e., ~ 1/17 above 3 MeV NOT bad ! * Above 3.5 MeV NO counts ! * Further ON / OFF Preliminary 2.9 MeV

“Ultra-Low-Energy” HPGe Prototype mass 5 g ; can be constructed in multi-array form 55Fe+Ti back-scattered Spectra : noise edge at 200 eV threshold <100 eV after modest PSD background measurement on-site Oct 03 study appl. in nN coherent scattering and Dark Matter searches PSD Cut Threshold ~ 200 eV Signal Band Threshold < 100 eV

R&D Projects Upgrading FADCs (+ FPGA etc. capabilities…..) Explore New Detectors Scenarios (LEn, CDM …)  loaded crystal scintillator (GSO, YbAG, LSO …..)  ultra low energy HPGe [ O(100 eV) threshold ] CsI(Tl) for Dark Matter Searches  CsI(Tl) CDM search @ Korea by KIMS Coll. Upgrading FADCs (+ FPGA etc. capabilities…..)  for LEPS @ SPring8 Trace Radio-purity with AMS ( Accelerator Mass Spectrometry)  1st goal : sensitivity of 10-14 g/g in 40K Sono-Luminescence Project (inter-disciplinary)

Also ………. Road tunnel at 2 km 100 m rock overburden Geographically possible for medium baseline experiment : Easy reach from city Access to Plant established Road tunnel at 2 km 100 m rock overburden

Summary & Outlook 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 ~ Underground CDM Expt. Results published on mn (Gn)  Other analyses under way Period-II DAQ  Improved HPGe Conf.  186 kg CsI(Tl) [s(ne) …]  study potentials for scoh(nN) …… Diversified R&D Program in parallel