1. Low Energy Neutrino Physics at the Kuo-Sheng Reactor Laboratory in Taiwan
Overview of TEXONO Collaboration
Kuo-Sheng Reactor Neutrino Laboratory
Results on Neutrino Magnetic Moments
Preliminary Results on Neutrino-Electron Elastic Scattering
R&D projects towards Neutrino-Nucleus Coherent Scattering
Survey of Other Research Program
Summary & Outlook
Lin,, Sin-Ted/ 林興德
On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration
Insititute of Physics, Academia Sinica / 9th CIPANP

2. Program: Low Energy Neutrino & Astroparticle Physics
TEXONO Collaboration
Collaboration : Taiwan (AS, INER, KSNPS, NTU) ; China (IHEP, CIAE, THU, NJU) ; Turkey (METU) ; USA (UMD) ; India (BHU)
Program: Low Energy Neutrino & Astroparticle Physics
Kuo-Sheng (KS) Reactor Neutrino Laboratory
reactor : high flux of low energy electron anti-neutrinos
oscillation expts.  mn0  anomalous n properties & interactions
n physics full of surprises , need intense n-source
study/constraint new regime wherever experimentally accessible
explore possible new detection channels
Diversified R&D Projects

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

4. Kuo Sheng Reactor Neutrino Laboratory
Front View (cosmic veto, shielding, control room …..)
Inner Target Volume
Fne (6.4 X 1012 /s )
n/fission
235U:
238U:
239Pu: 1.8
241Pu: 0.4
U (n,g) 1.2
Configuration: Modest yet Unique
Flexible Design: Allows different detectors conf. for different physics

5. Reactor Neutrino Interaction Cross-Sections
mass
quality
Detector requirements
R&D :
Coh. (nN)
T < 1 keV
Results & More Data:
mn(ne)
T ~ keV
On-Going Data Taking & Analysis
SM s(ne)
T > 3 MeV

6. KS Experiment: Period I, II, III Detectors
ULB-HPGe [1 kg]
CsI(Tl) Array
FADC Readout
[16 ch., 20 MHz, 8 bit]
Multi-Disks Array [1 Tb*5]

7. Magnetic Moment Searches @ KS
Neutrino Electromagnetic Properties
simple compact all-solid design : HPGe (mass 1 kg) enclosed by active NaI/CsI anti-Compton, further by passive shielding & cosmic veto
selection: single-event after cosmic-veto, anti-Comp., PSD

8. Combined Analysis with all Information :
Denote
TEXONO data -1st 90, (2003) .
background comparable to underground CDM experiment : ~ 1 day-1keV-1kg-1 (cpd)
DAQ threshold 5 keV
analysis threshold 12 keV
The limit based on 570.7/127.8 days of
Reactor ON/OFF:
mn(ne) <7.2 X mB (90% hep- ex /

9. Search of mn at low energy
high signal rate & robustness:
mn>>SM [ decouple irreducible bkg  unknown sources ]
T<<En  ds/dT depends on total fn flux but NOT spectral shape
[ flux well known :
~6 fission-n  ~ U capture-n
per fission ]
Neutrino radiative decay

10. nee scattering
However, SM >>MM at few MeV ! The differential cross section can
be represented

11. CsI(Tl) Array (~200 kg) : s(ne)
Data analysis under way ..
(25000/8000 day-kg for ON/OFF in PI,II,III)
Single Crystal QL Vs QR (Raw Data)
Region of Interest for SM s(ne)
Z = 0 cm
208Tl
40K
137Cs
Z =40 cm

12. Preliminary Result Goal Further analysis =>reduce the background
PSD on e/g in few MeV region
X 4 data
Background understanding and suppression (Cosmic ray, g cascades of 208Th, Pair Production)
Global analysis of all spectra
Goal
The best fit of based on 6500/ 3600 day*kg for Reactor of ON/OFF
at 3-8MeV
at 3.5-8MeV

13. Neutrino-Nucleus Coherent Scattering
Standard Model Cross-Sections:
a fundamental neutrino interaction never been experimentally-observed
s~N2 applicable at En<50 MeV where q2r2<1
a sensitive test to Standard Model
(Say, with Q.F.=0.25; Bkg ~1 cpd; Threshold~100eV, the Signal-to-Background ratio~ 20)
an important interaction/energy loss channel in astrophysics media
a promising new detection channel for neutrinos, without strict lower bound on En & the channel for WIMP direct detection !
involves new energy range at low energy, many experimental challenges & much room to look for scientific surprises

14. “Ultra-Low-Energy” HPGe Prototype
ULEGe – developed for soft X-rays detection ; easy & inexpensive & robust operation
Prototype : (I) 5 g ; (II) 4 X 5 g ; (III) 10 g ; (IV) segmented 20 g
threshold <100 eV after modest PSD
[lowest achieved for bulk radiation detectors]
study feasibilities for 1-kg-ish detector for nN coherent scattering and Dark Matter searches
[ mn search  mB ]
5 g
4 X 5 g
Threshold < 100 eV

15. min. 700 m of rock overburden
TEXONO  Y2L
Install 5 g ULB-ULEGe at Y2L on January 2005
Study background and feasibility for CDM searches
may evolve into a full-scale (1 kg) CDM experiment
Yangyang (襄陽) Lab (Y2L)
min. 700 m of rock overburden
Sensitivity Plot for
CDM-WIMP search with
1 kg ULEGe at 100 eV threshold ..

16. Survey for other research program
Evaluate ne flux at standard reactors \ Explore ne flux enhancement in loaded reactor (e.g. with Rev. D 72, (2005)
Looking for n-induced nuclear transition
Search for reactor axions
* Reactor core has intense M1 transitions : e.g. 7Li, 91Y, 97Nb etc.
Trace Radio-purity measured with AMS
* develop quick\small sample techniques ( e.g. 40K g/g)

17. Summary & Outlook TEXONO Collaboration:
 Built-Up from Scratch & Maturing
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) & reactor ne
Diversified Program in Parallel
Main Thrust on  ~200 kg CsI(Tl) [s(ne) …]
 ULEGe: for scoh(nN) + CDM ;