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

Status on Neutrino-Electron Elastic Scattering

R&D projects towards Neutrino-Nucleus Coherent Scattering

(coupled with H.Wong’s talk)

Summary

Lin,, Shin-Ted/ 林興德On Behalf of Taiwan Experiment On NeutrinO (TEXONO) Collaboration

Institute of Physics, Academia Sinica / 中央研究院@ TAUP2007,sendai Japan

TEXONO Collaboration

Collaboration : Taiwan (AS, INER, KSNPS, NTU) ;

China (IHEP, CIAE, THU, NJU) ;

Turkey (METU) ; India (BHU) ; Korea (KIMS)

Program: Low Energy Neutrino & Astroparticle Physics

Kuo-Sheng (KS) Reactor Neutrino Laboratory oscillation expts. m0 anomalous properties & interactions

reactor : high flux of low energy electron anti-neutrinos

physics full of surprises , need intense -source

※ study/constraint new regime wherever experimentally accessible

※ explore possible new detection channels

Kuo-Sheng Nuclear Power Plant

KS NPS-II : 2 cores 2.9 GW

KS Lab: 28 m from core#1

Kuo Sheng Reactor Neutrino Laboratory

Configuration: Modest yet Unique

Flexible Design: Allows different detectors conf. for different physics

Front View (cosmic veto, shielding, control room …..)

Inner Target Volume

Reactor Neutrino Spectrum

/fission

235U:3.4 238U:0.5 239Pu:1.8 241Pu:0.4 U (n,) 1.2

e) ~ 6.4X1012 / sec*cm2

Reactor Operation Data

R&D : Coh. (N)

T < 1 keV

Results on (e) @T ~ 1-100 keV

ddT)>> (ddT)SM

T<<E ddT ∝ 1/T

T << E ddT depends on total flux but NOT spectral shape

On-Going Data Taking & Analysis SM (e)

T > 3 MeV

Reactor Neutrino Interaction Cross-Sections

massquality Detector requirements

22

11)(2

ETmedT

de

KS Experiment: Period I, II, III,IV,V Detectors

FADC Readout

[16 ch., 20 MHz, 8 bit]

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

Multi-Disks Array [few Tbs]

8

Neutrino Electromagnetic Properties : Magnetic Moments

• fundamental neutrino properties & interaction ; necessary consequences of neutrino masses/ mixings

• Astrophysics bound on

10-10 – 10-12 Bhowever, model dependence

• Study of anomalous e scattering is valid for

- both Dirac/Majorana - both Diagonal/Transition i j

Minimally Extended Standard Model:

However, many models can enhance it

significantly (M, WR …..)

Magnetic Moment Searches @ KS

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

Data Analysis

TEXONO data

(570.7/127.8 days of Reactor On/OFF)

background comparable to underground CDM experiment : ~ 1 day-1keV-1kg-1 (cpd)

DAQ threshold 5 keV analysis threshold 12 keV

Combined all information

i / f i / f Before/After cuts

Spectrum ;

SM

Reactor On/Off

e (SM) e2 e

+/ -

i

f

i

f

ff

11

• Systematic effects

• Best-fit

The limit based on 570.7/127.8 days of Reactor ON/OFF: e) <7.4 X 10-11 B (90% CL) @ PRD 75 2007

Results on neutrino magnetic moment

e (SM) e2 ee X10 -1

0 B

e2 = ±0.59 0.53 ־ (stat.) ± 0.18(sys.)

Search of at low threshold high signal rate & robustness:

Gemma prelim. Result:

e) <5.4 X 10-11 B (90% CL) @hep-ex0705.4576v1

22

11)(2

ETmedT

de

Neutrino radiative decay

13

ee scattering

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

SM MM

CsI(Tl) Array (~200 kg) : e)

Z =40 cm

Single Crystal QL Vs QR

(Raw Data)

Region of Interest for SM e)

Z = 0 cm

208Tl

40K 137Cs

Data analysis under way ..

(40000/12000 day-kg for ON/OFF in PII to PV)

15

Status of neutrino-electron scattering

Background understanding

and suppression

--Multiple-hit analysis (Cosmic ray tagged, cascades of 208Th )

=> sin2w @6900/2300day*kg of reactor ON/OFF

X 3 data

Global analysis of all spectra

Expect:

a fundamental neutrino interaction never been experimentally-observed ; a test of standard model (T. Rashba’s talk)

an important interaction/energy loss channel in astrophysics media

R&D on an ULEGe towards (kg-scale ; 100eV threshold ; 1cpd) experiment : allow for CDM search ( H.Wong’s talk) & improve the neutrino magnetic moment [ search ~10-11 B ]

Neutrino-Nucleus Coherent Scattering

17

Kuo-Sheng Neutrino Lab.: Modular & Flexible Design Physics Data Taking since 2001 ※ Unique HPGe Low Energy Data ※ Bkg Level ~ Underground CDM Expment

Results published on (PRL 03;PRD 07)& reactor e (PRD 05) and axion ( PRD 07 HM Chang’stalk )

Diversified Program in Parallel

Main Thrust on ~200 kg CsI(Tl) [(e) …]

ULEGe: for coh(N) + CDM (H.Wong’s talk)

Summary & Outlook