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
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Program:
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) ]
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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.
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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
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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)
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KS Expt: Period I Detectors
ULB-HPGe [1 kg]
FADC Readout
[16 ch., 20 MHz, 8 bit]
CsI(Tl) [46 kg]
Multi-Disks Array [800 Gb]
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 mn
mn with Reactor ne
 parametrize possible niL njR + g vertices
  both i = j “diagonal” & i  j “transition”
moments
 Experimental Probe:
 Study
n e + e-  n X + e Focus on low recoil energy
※ sm  T–1
※ decouples SM “background”
Electron Recoil Spectra
[ ……… 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
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KS/P1/Ge/mn Data
 Data Volume:
 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
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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)
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Reactor mn(ne) Sensitivities
Gn Sensitivities
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Status & Plans
HPGe [1 kg] :
 mn + Gn : x2 more data
improved background & analysis
 study ne flux from reactor
dominated by 51Cr : n e n e ~ 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
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Reactor Neutrino Interaction Cross-Sections
P2: SM
(ne) > 2
MeV
P3+: Coh.
(nN) <
1 keV
P1:
MM (ne)
1-100 keV
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-
Tagging of 73Ge ½ 2g transitions:
Event-by-Event backgroundfree 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
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Period-2 CsI(Tl) Array : 186 kg, 93 crystals
Single Crystal QL Vs QR (Raw Data)
Z = 0 cm
Z =40 cm
208Tl
137Cs
40K
Region of Interest for SM s(ne)
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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-ray, & Z-pos
SEH, SCH, & Cosmic
SEH, SCH
SEH, SCH
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SEH, SCH
Data Analysis Techniques
Normal Event Pulse
Defining Cuts:
2] Special Cuts –
a) Alpha Event Cut
(having fast decay
time)
Alpha Event Pulse
A; .
Check- Alphas are located
around 2 MeV
Select- event having Time
average less than 40
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Data Analysis Techniques
Defining Cuts:
2] Special Cuts –
c) Right side Double
Pulse Cut
A;
Select – Event having
Larger Time Avg.
but low charge !
Right side Double Pulse
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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
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Period-2 CsI(Tl) Array : 186 kg, 93 crystals
Integrated Event Count for CsI(Tl)
Preliminary
* 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
2.9 MeV
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“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
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R&D Projects
 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)
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Also ……….
Geographically possible for
medium baseline experiment :
 Easy reach from city
 Access to Plant established
 Road tunnel at 2 km
 100 m rock overburden
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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
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