Transcript ASIoP Workshop, Nov04

Hightlights and Status of the TEXONO
Research Program on Low Energy Neutrino
& Dark Matter Physics
 TEXONO Collaboration & Kuo-Sheng Laboratory & Program
Overview
 Results on Neutrino Magnetic Moments, Reactor Electron
Neutrinos and Reactor Axion Search
 Future Direction - Ultra-Low Energy Detectors for NeutrinoNucleus Coherent Scattering & Dark Matter Searches
 Outlook.
Henry T. Wong / 王子敬
Academia Sinica / 中央研究院
November 2007
KIMS-TEXONO
Workshop
Seoul National U.
TEXONO Collaboration
Taiwan EXperiment On NeutrinO
Collaboration :
 Taiwan (AS, INER, KSNPS, NTU,NCU,NCCU)
 China (IHEP, CIAE, THU, NJU, NKU)
 Turkey (METU)
 India (BHU)
+ Close Partnership (KIMS Collaboration in S. Korea)
Poineering Efforts :
“Zero-Background Experiment” !
 KS Expt: 1st large-scale particle physics experiment in Taiwan
 TEXONO Coll. : 1st big research Coll. % Taiwan & China
Neutrino Physics at (L~0) Reactor ??
Rationale :
 Need neutrino source to do neutrino physics : reactor
is a high-flux, understood and controlled source 
AND free as well !!
 oscillation expts.  mn0  anomalous n properties &
interactions
 Experimental neutrino physics has been full of surprise
 Worth exploring any experimentally accessible
parameter space
 May place constraints to interpretation of precision
oscillation data
 Explore new neutrino sources & detection channels for
future studies
Kuo-Sheng Nuclear Power Plant
KS NPS-II : 2 cores  2.9 GW
NPS-IV
Kuo Sheng Reactor Neutrino Laboratory
Front Gate
28 m from core#1 @ 2.9 GW
Shallow depth : ~30 meter-water-equivalent
Reactor Cycle : ~50 days OFF every 18 months
Front View (cosmic vetos,
shieldings, control room …..)
Configuration: Modest yet Unique
Flexible Design: Allows different
detectors conf. for different physics
Inner Target Volume
KS Laboratory : Detectors
ULB-HPGe [1 kg]
CsI(Tl) [200 kg]
FADC Readout
[16 ch., 20 MHz, 8 bit]
ULE-ULB-HPGe
Prototype [20 g]
Multi-Disks Array [600 Gb]
Reactor Neutrino Spectra Evaluation…
Reactor Operation Data
ne
Nuclear Physics
Reactor Neutrino Interaction Cross-Sections
quality
Detector requirements
mass
1 counts /
kg-keV-day
R&D :
Coh. (nN)
T < 1 keV
Threshold ~
100 eV
Completed Results :
mn(ne) : T~1-100 keV
Axions : T ~ keV-MeV
On-Going Data
Taking &
Analysis
SM s(ne)
T > 2 MeV
Research Program of TEXONO :
 Search of Neutrino Magnetic Moments [this talk]
 Studies of Reactor Electron Neutrino [this talk]
 Search of Reactor Axions [this talk]
 Measurement of neutrino-electron scattering crosssections (i.e. sin2qW at MeV range) with CsI(Tl)
crystals [M.Deniz’s talk]
 Studies of possible neutrino induced nuclear transitions
in Ge & CsI [F.K.Lins’ talk]
 Measurement of Trace-Radiopurity with Accelerator
Mass Spectrometry [Results Published on I129, K40;
Omitted]
 Sonoluminescence [F.K. Lin’s talk]
Future Direction [This+H.B.Li’s+S.K.Lin’s talk]:
 Open new detection channel and detector window down
to 100 eV
 testing “ULEGe” prototypes at AS+KS+Y2L
 sub-keV Quenching Factor measurements at CIAE
 Physics Goals:
 First observation of neutrino-nucleus coherent
scattering at KS
 Dark Matter Searches at low-WIMP-mass region at
Y2L
 Improvement on Neutrino Magnetic Moment
sensitivities
 Expect ready for a major experiment with ~1 kg scale
detector at 2008+ [scale : O(1 MUSD )]
Neutrino Electromagnetic Properties : Magnetic Moments
requires mn0
e.g.
 a conceptually rich subject ; much neutrino physics &
astrophysics can be explored
n-osc. : Dmn , Uij
0nbb : mn , Uij , nD/nM
mn
: mn , Uij , nD/nM , n  g
 fundamental neutrino properties & interaction ; necessary
consequences of neutrino masses/ mixings ; in principle can
differentiate Dirac/Majorana neutrinos
 explore roles of neutrinos in astrophysics
Magnetic Moment Searches @ KS
 simple compact all-solid design :
HPGe (mass 1 kg) enclosed by
active NaI/CsI anti-Compton,
further by passive shieldings &
cosmic veto
 selection: single-event after
cosmic-veto, anti-Comp., PSD
 TEXONO data (571/128 days)
ON/OFF) [PRL 90, 2003 ; PRD
75, 2007]
 background comparable to
underground CDM experiment :
~ 1 day-1keV-1kg-1 (cpd)
 DAQ threshold 5 keV
analysis threshold 12 keV
ON/OFF Residual Plot :
Limit:
mn(ne) < 7.4 X 10-11 mB @ 90% CL
Direct Experiments at Reactors
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 ]
gn Couplings : Neutrino Radiative Decays
First exploration of electron-neutrino
production at reactors ….
Electron Neutrinos @ Reactor
 Evaluate ne flux at standard
reactors
 Derive limits on mn and Gn for
ne
 Explore ne flux enhancement
in loaded reactor (e.g. with
Cr)
 Study Potential applications :
 neNCC cross-section
measurements,
 q13
 Pu-production monitoring
(PRD 72, 2005)
Nuclear material
Fission
products
n
Structure
material
EC
EC
n rich nuclei
b－decay
n rich nuclei
b－ decay
Stable isotope
electron
antineutrino
emission
even-even
Stable isotope
Electron
neutrino
emission
Regular
Reactor :
X 10-4
Loaded
Reactor :
c.f. ~7.2
n e /fission
Exploration of possible axion emission at reactor …..
PRD 75 (2007)
 Idea : Axions can be emitted in gamma-decays
AND the power reactor is THE most powerful
terrestrial radioactivity source.
 Production:
 Experimental
Search :
 Detection:
Results:
 Improved laboratory limits on gaee for Bra>10-9
 Exclude DFSZ/KSVZ Models for axion mass 104-106 eV
“Ultra-Low-Energy” HPGe Detectors
 ULEGe – developed for soft X-rays detection ; easy &
inexpensive & robust operation
 Prototypes built and studied :
 5 g @ Y2L
 4 X 5 g @ KS/Y2L
 10 g @ AS/CIAE
 segmented 180 g @ AS/KS
 Being built : 500 g single element
 Physics for O[100 eV threhold1 kg mass1 cpd
detector] :
 nN coherent scattering
 Low-mass WIMP searches
 Improve sensitivities on mn
 Implications on reactor operation monitoring
 Open new detector window & detection channel
available for surprises
ULEGe-Prototype built & being studied :
5 g
10 g
43mm
4 X 5 g
DETECTOR VIEW INSIDE ENDCAP
AND INPUT STAGE LOCATIONS
Input stage
location of the
preamplifier
Signal side
S1
B
20mm
S2
A
S1
43mm
S2
10
mm
S3
S4
ENDCAP
Diameter :
<85mm
Crystal
Holder
AB view
Crystal
Copper
shielding to
be defined
Segmented 180 g
with dual readout
20mm
S4
A
S3
B
High Voltage
side
Cooling finger
R&D Program towards Realistic O(1 kg) Size
Experiments (both nN & CDM) :
 measure & study background at sub-keV range at KS &
Y2L ; design of active & passive shielding based on this.
 compare performance and devise event-ID (PSD &
coincidence) strategies of various prototypes
 devise calibration & efficiency evaluation schemes
applicable to sub-keV range
 measure quenching factor of Ge with neutron beam
 study scale-up options ULEGe-detector
 Keep other detector options open
Sensitivity Plot for CDMWIMP direct search for
100 eV threshold
detector [First Results :
LHB’s talk]
Low (<10 GeV) WIMP Mass / Sub-keV Recoil Energy :
 Not favored by the most-explored specific models on galacticbound SUSY-neutralinos as CDM ; still allowed by generic SUSY
 Solar-system bound WIMPs require lower recoil energy detection
 Other candidates favoring low recoils exist: e.g. non-pointlike
SUSY Q-balls.
 Less explored experimentally
Quenching Factor Measurement for Ge at
CIAE’s Neutron Facilities:
With 13 MV Tandem
Goals for Dec 07 Runs :
 Use actual ULEGe 100-eV detector
 Use lower energy neutron beam with
a pulsed-LE tandem
Detector Scale-up
Plans:
p
S1
S0
 500-g, single-element, modified coaxial HPGe design,
inspired by successful demonstration of Chicago group
(nucl-ex/0701012)
 Position-sensitive from drift-profile pulse shape
 Dual-electrode readout and ULB specification
 Being prepared, available first-half 2008.
Road Map ……
Improved PSD ;
dual-readout
coincidence
Scale up to compact 1 kg ;
understand background
source (g/n) ; improved
shielding design
State-of-the-Art(Science)
 An O[100 eV threshold1 kg mass1 cpd detector]
has interesting applications in neutrino and dark
matter physics, also in reactor monitoring
 Open new detector window & detection channel :
potentials for surprise
 Mass Scale-Up: recent demonstration of realistic
design
 Threshold – ~300 eV at hardware level, intensive
studies on software techniques to aim at ~100 eV, &
on their stabilities and universalities
 Prototype data at reactor already provide competitive
sensitivities for WIMP search at mass<10 GeV .
 Sub-keV Background understanding and suppression –
under intensive studies
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 & axions
 Diversified Program in Parallel
Main Thrust on  ~200 kg CsI(Tl) [s(ne) …]
 ULEGe: for scoh(nN) + CDM Search