Download ppt - 中央研究院物理所

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 / 中央研究院@ 9th CIPANP
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
Kuo-Sheng Nuclear Power Plant
KS NPS-II : 2 cores  2.9 GW
KS n Lab: 28 m from core#1
Kuo Sheng Reactor Neutrino Laboratory
Front View (cosmic veto,
shielding, control room …..)
Inner Target Volume
Fne (6.4 X 10
12
/s )
Configuration:
n/fission
Modest yet Unique
235U:
Flexible Design:
3.4
238U:
0.5
239Pu: 1.8
241Pu: 0.4
U (n,g) 1.2
Allows different
detectors conf. for
different physics
Reactor Neutrino Interaction Cross-Sections
quality
Detector requirements
On-Going
Data Taking
& Analysis
R&D :
Coh. (nN)
T < 1 keV
mass
Results & More Data:
SM s(ne)
mn(ne)
T > 3 MeV
T ~ 1-100 keV
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]
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 cosmicveto, anti-Comp., PSD
Combined Analysis with all Information :

Denote
F i- ; F i for the reactor OFF/ON data ;
After ACV  CRV cuts, it turns into F f / F f
n  SM  mn
F f   n  F f
F f   n
F f
 i
i
F  n
F
 TEXONO data -1st results @PRL 90, 131802
(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 10-11 mB (90% CL) @ hep- ex /0605006
ds (ne)   2  1  1  m 2
m
dT
me2 T En  n
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  ~1.2 238U capture-n
per fission ]
Neutrino radiative decay
nee scattering
However, SM >>MM at few MeV ! The differential cross section can
be represented
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)
Z = 0 cm
Z =40 cm
208Tl
137Cs
40K
Region of Interest for SM s(ne)
Preliminary Result
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)
The best fit of
based on 6500/ 3600 day*kg
for Reactor of ON/OFF
 Global analysis of all spectra
0.37+- 0.13 at 3-8MeV
0.30+- 0.22 at 3.5-8MeV
Goal
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
“Ultra-Low-Energy” HPGe Prototype
 ULEGe – developed for soft X-rays detection ;
easy & inexpensive & robust operation
5 g
 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  10-11 mB ]
4 X 5 g
Threshold
< 100 eV
TEXONO  KIMS @ 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
Sensitivity Plot
for
CDM-WIMP
search with
1 kg ULEGe at
100 eV
threshold ..
Yangyang (襄陽)
Lab (Y2L)
min. 700 m of rock
overburden
Survey for other research program
 Evaluate ne flux at standard reactors \ Explore ne flux
enhancement in loaded reactor (e.g. with Cr) @Phys. Rev. D 72,
012006 (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
10-16 g/g)
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