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 Neutrino-Nucleus Coherent Scattering & Dark Matter Searches

Outlook.

Henry T. Wong / 王子敬

Academia Sinica / 中央研究院

November 2007

Hightlights and Status of the TEXONO Research Program on Low Energy Neutrino

& Dark Matter Physics

KIMS-TEXONO

WorkshopSeoul

National U.

@

TEXONO Collaboration

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)

Taiwan EXperiment On NeutrinO

Poineering Efforts : “Zero-Background Experiment” ! KS Expt: 1st large-scale particle physics experiment in Taiwan

TEXONO Coll. : 1st big research Coll. % Taiwan & China

Need neutrino source to do neutrino physics : reactor is a high-flux, understood and controlled source AND free as well !!

oscillation expts. m0 anomalous 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

Neutrino Physics at (L~0) Reactor ?? Rationale :

Kuo-Sheng Nuclear Power Plant

KS NPS-II : 2 cores 2.9 GW

NPS-IV

28 m from core#1 @ 2.9 GWShallow depth : ~30 meter-water-equivalentReactor Cycle : ~50 days OFF every 18 months

Kuo Sheng Reactor Neutrino Laboratory

Front Gate

Configuration: Modest yet Unique

Flexible Design: Allows different detectors conf. for different physics

Inner Target Volume

Front View (cosmic vetos, shieldings, control room …..)

FADC Readout

[16 ch., 20 MHz, 8 bit]

ULB-HPGe [1 kg] CsI(Tl) [200 kg]

Multi-Disks Array [600 Gb]

KS Laboratory : Detectors ULE-ULB-HPGe

Prototype [20 g]

Reactor Neutrino Spectra Evaluation…

Nuclear Physics

e

Reactor Operation Data

R&D : Coh. (N)

T < 1 keV Completed Results :(e) : T~1-100 keV

Axions : T ~ keV-MeV

On-Going Data Taking & Analysis SM (e)

T > 2 MeV

Reactor Neutrino Interaction Cross-Sections

massquality Detector requirements

1 counts / kg-keV-day

Threshold ~ 100 eV

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 cross-sections (i.e. sin2W 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

e.g.

requires m0

a conceptually rich subject ; much neutrino physics & astrophysics can be explored

-osc. : m, Uij

0: m, Uij , D/M

: m, Uij , D/M ,

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

Limit:e < 7.4 X 10-11 B @ 90% CL

ON/OFF Residual Plot :

Search of at low energy high signal rate & robustness:

>>SM [ decouple irreducible bkg unknown sources ]

T << E d/dT depends on total flux but NOT spectral shape [ flux well known : ~6 fission- ~1.2 238U capture-per fission ]

22

11)(2

ETmedT

de

Direct Experiments at Reactors

Couplings : Neutrino Radiative Decays

First exploration of electron-neutrino production at reactors ….

Electron Neutrinos @ Reactor (PRD 72, 2005)

Nuclear material

Fission products

n rich nuclei

n rich nuclei

Stable isotopeStable isotope

Structure materialn

decay

decay

EC EC

even-even

Electron neutrino emission

electron anti-neutrino

emission

Evaluate e flux at standard reactors

Derive limits on and for e

Explore e flux enhancement in loaded reactor (e.g. with Cr)

Study Potential applications : eNCC cross-section

measurements, 13 Pu-production

monitoring

Regular Reactor :

Loaded Reactor :

c.f. ~7.2 /fission e

X 10-4

Exploration of possible axion emission at reactor …..

Idea : Axions can be emitted in gamma-decays AND the power reactor is THE most powerful terrestrial radioactivity source.

PRD 75 (2007)

Production: Detection:

Experimental Search :

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 threhold1 kg mass1 cpd

detector] : N coherent scattering Low-mass WIMP searches Improve sensitivities on Implications on reactor operation monitoring Open new detector window & detection channel

available for surprises

ULEGe-Prototype built & being studied :

5 g 10 g 4 X 5 g

Signal side

High Voltage side

A B

AB view

A B

43mm

43m

m10 m

m

20mm

20m

m

S3

S1

S2

S4

Segmented 180 g with dual readout

S1

S2

S3

Input stage location of the preamplifier

CrystalHolder

Crystal

ENDCAPDiameter :

<85mm

DETECTOR VIEW INSIDE ENDCAP AND INPUT STAGE LOCATIONS

Cooling finger

S4

Copper shielding to be defined

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

R&D Program towards Realistic O(1 kg) Size Experiments (both N & CDM) :

Sensitivity Plot for CDM-WIMP 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 galactic-bound 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:

Goals for Dec 07 Runs : Use actual ULEGe 100-eV

detector

Use lower energy neutron beam with a pulsed-LE tandem

With 13 MV Tandem

Detector Scale-up Plans:

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.

SS

p

Scale up to compact 1 kg ; understand background source (/n) ; improved shielding design

Improved PSD ; dual-readout coincidence

Road Map ……

An O[100 eV threshold1 kg mass1 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

State-of-the-Art(Science)

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 ExptResults published on , reactor e & axions

Diversified Program in Parallel Main Thrust on ~200 kg CsI(Tl) [(e) …] ULEGe: for coh(N) + CDM Search

Summary & Outlook