Prospect of experiment in Korea

Presented by H.J.Kim Yonsei Univ., 10/25/2003 KPS 2003 fall meeting

Contents

1) Introduction of 2) Theory and Experiments of 0, 2 3) EC++ and transition to excited state with HPGe and CsI crystal with coincidence (Zn, Sn

study)4) Metal Loaded Liquid Scintillator R&D for 5) 0, 2 R&D with Crystals.6) Prospect

Age of physics !What we knew : spin 1/2, no charge 3 type:

eby Z line shape)

What we now know: oscillations ->mass, mixing Solar, Atmospheric, Reactor, K2K, LSND(miniBooNe)

What we still don't know and need to know a) Magnetic moment (Reactor, source b) Absolute mass scale (tritium ) c) Dirac or Majorana ( =? anti ) ()

Cosmological question Relic , Ultra high energy Dark matter

Neutrino mass limits

mass limits from high energy

But it is difficult to reach ~eV sensitivity

Double beta decay process

(A,Z) -> (A,Z+2) + 2 +2(A,Z) -> (A,Z-2) + 2 +2 EC+ ,2EC

also is possible

(A,Z)(A,Z+1)

(A,Z+2)

(A,Z)(A,Z-1)

(A,Z-2)

Excited state

Ground state

-> keV)

Why decay is important?

2-DBD Candidate and Experimental results

1 1017- 2 1022(8.0 ± 0.7) 1018100Mo

6 1016- 4 1020(7.0 ± 1.7) 1018150Nd

3 1017- 6 1020(2.1+0.8-0.4) 101996Zr

1.2 1019(2.0 ± 0.6) 1021238U

2 1019- 7 1020(0.9 ± 0.15) 1021130Te

9 1022- 3 1025(2.5 ± 0.4) 1024128Te

3 1018- 2 1021(3.3 +0.4-0.3) 1019116Cd

5 1019- 2 1021(6.8 ± 1.2) 1020100Mo(0+*)

3 1018- 6 1021(0.9 ± 0.1) 102082Se

6 1018- 5 1020(4.2 +2.1-1.0 ) 101948Ca

7 1019- 6 1022(1.42 +0.09- 0.07) 102176Ge

T1/22(y)calcT1/2

2(y)Isotope

Weighted average of all positive resultsWeighted average of all positive results

0 decay half lives uncertainty

A VARIETY OF 0A VARIETY OF 0-DBD-DBD CANDIDATE NUCLIDES HAS TO BE STUDIED CANDIDATE NUCLIDES HAS TO BE STUDIED

The Best 0The Best 0-DBD-DBD results with different nuclei results with different nuclei

1.8

<m>* (eV)

6.0> 1.8 102248CaOgawa I. et al., submitted 2002

Belli et al.

Experiment

< 1.4 4.1> 7 1023136Xe

Range <m>T1/20(y)Isotope

1.01.94.80.380.35

Bernatowicz et al. 1993

Zdenko et al. 2002

Ejiri et al. 2001

Aalseth et al 2002

Klapdor-Kleingrothaus et al. 2001

1.5Mi DBD 2002 < 0.9 2.1> 2.1 1023130Te< 1.0 - 4.4> 7.7 1024128Tegeo

< 1.8 6.2> 1.3 1023116Cd< 1.4 - 256> 5.5 1022100Mo< 0.3 - 2.5> 1.57 1025

< 0.3 2.5> 1.9 102576Ge

evidence?

Future projects

0.1 - 1

34 nat

1 10

10nat

1.6enr

0.8 nat

1 10

1 nat. enr.

0.5

Mass [ton]

2.3 1028 y

600

300

1000

10

330

1500

300

150

old/future

bkg

4.9 1027 y

1.3 1028 y

2.2 1028 y

5 1027 y

INR - Kievneeds

confirm.

ELEGANTstandard

Gotthard Xe

challenging

DAMA - Xetested

MI-DBDtested

HD-Mpartially tested

HD-Mpartially tested

IGEXmature

Technology

2 - 6 1028 y

0.1 1 1028 y

0.4 1028 y

0.06

0.06

GENIUS

GEM

MAJORANA

1 1027 y0.33CUORE

0.9 - 13 1027 y

0.5 - 1 1027 y

0.025

0.06

EXO

XMASS

0.1 - 1 1027 y0.03CAMEO

1 1027 y~ 0.02MOON

Sensitivity (10y)

present bkg

[c/keV kg y]

SvOutPlaceObjectSvOutPlaceObject

meV 10m

* Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31* Staudt, Muto, Klapdor-Kleingrothaus Europh. Lett 13 (1990) 31

Experimental search for Experimental search for DBDDBD

Two approaches:

+ event shape reconstruction- low energy resolution

e-

e-

source

detector

detector

Source Detector

e-

e-

Source Detector(calorimetric technique)

+ high energy resolution- no event topology

sum electron energy / Q

Signature: shape of the two electron sum energy spectrum

1

10-2

10-6

R = 5%

If you use the calorimetric approach

material requirements

Matrix elements: good one (ex: Nd) ~m

1/2

Enrichment: Gd, Te ~20%; Zr, Nd -> Difficult ~m1/2

Mo, Se, Ge, Kr, Xe, (Cd, Sn) ->Easy

Efficiency : ~ 100% for active source technique ~m1/2

Mass, time ; ~m

1/4

Resolution; 2 background issue ~m1/4

Background; Source impurity (U238,Th232) ~m1/4

Source purification, Time correlation (PSD)

Active shielding to reduce backgrounds

Why high-Z loaded scintillator for

Advantage a) Some high-Z can't be used for inorganic

scintillator. (Sn) b) high-Z can be loaded to LS (>50% or more) c) Fast timing response (few ns) d) Low cost of LS, Large volume is possible e) U/Th/K background for LS is low and

purification is known f) separation can be possible

Disadvantage a) Bigger volume is necessary (C,H in LS, low

density) b) Moderate light output (~15% of NaI(Tl))

Background of homemadeLSC

Tin loading study Tin compound 1) 2-Ethyl hexanoate (144g/mole), Tin 15% w 50%

loading (CH3(CH2)3CH(C2H5)CO2)2Sn ( FW405) => Quanching

2) Tetramethyl-tin (40%w50%) : flammable,expensive 3) Tetrabutyl-tin (19%w50%) 4) Dibutyltin diacetate, Dibutylphenyltin, tetrapropyltin, Tetraethyltin, DimethyldiphenyltinLS : Solvent+Solute * Solvent ; PC, 1,2-MN, o-,p-Xylene, Tolune, Benzene.. * Solute ; POP, BPO, PBD, Butyl-PBD, Naphthalene.. * Second-solute ; POPOP, M2-POPOP, bis-MSB...* PSD possible? -> Need a study* Others ; Nd2-ethylhexanoate, Zr4-ethylhexanoate. Ce2-ethylhexanoate, Sr2-ethylhexanoate, Pb2-

ethylhex.

Tin loading

Tin loading (TBSN 50%->20%Sn)

Double beta; HPGe with CsI crystal

HPGe a) EC++ , ++ ; No observation yet b) Excited transition to Mo, Nd (new)

HPGe + CsI (top side only) ; Under study (Zn,Sn, Zr) HPGe + Full CsI cover ; Improve sensitivity 1 order? => Confirm Nd and try for Zr,Sn excited transition => at Y2L, Uses 12 6x6x30cm existing crystal and existing RbCs PMT

HPGe + Active detector (Sn-LSC, CaMoO4, ZnSe)

W/o shielding

10cm Pb + 10 cm Cu+ N2(16 days data taking)

100% HPGe installed in CPL

Background measurement

Shielding

Sn-124, Sn-122 0-,2- limit

* World best limit on Sn-124 (E.Norman PLB 195,1987)

Test of TBSN for a week at CPL , Preliminary results 450cm3 HPGe, 140 hours , 1.0liter TBSN : 400g of

Sn 2+ (603keV) 3.8x1018 year (4.0x1019 year) 0+ (1156) 1.1x1019 year (2 - theory : 2.7x1021) 0+ (1326) 1.3x1019 year (2.2x1018 year)* Sn-122 EC++ decay ; 1.5x1018 year (6.1x1013)

Zn EC++ decayEC++ limit ( + -> 2 decay)

Positve evidence by I.BIKIT et.al,App. Radio. Isot. 46, 455, 1995<= 25% HPGe + NaI(Tl) with 350g Zn at surface with shielding. -> Need to confirm or disprove!

99.7% CL

Zn EC++ decay

HPGe + Zn(8x8x1cm)+CsI(Tl) crystalOur advantage: 100% of HPGe 350m underground 10cm low background lead, 10cm copper and N2 flowingCalibration by Na22 (+ radioactive

source)Efficiency calculation by Geant4; 3%Very Preliminary result with 1 week

data;Coincidence cut with 2 sigma range ;

1 event2x1020 year by 95% CLIf I.BIKIT’s central value is taken, we

would observe 100 events (1.1x1019 y)

Sn (8x8x1cm) data is available and we can set 5 orders better limit

511keV

511keV

CsI7.5x7.5x8

Zn

HPGe

Energy dist at HPGe

Crystals for 300g CdWO4 search by Ukrine group;

>0.7x1023 years Enrichment, PSD, actvie shielding -> successful CaMoO4 (PbMoO4 , SrMoO4...) ; Mo, Ca search Similar with CdWO4 Light output; 20% at 20deg, increasing with

lower temp, Decay time; weak 4ns and 16.6micro sec Wavelength; 450-650ns-> RbCs PMT or APD PSD?; -> Crystal growth issue; no commercial -> PSU -> Active (CsI) shielding inside of Y2L GSO, ZnSeCdZnTe ; R&D, 0.5x0.5x05cm(1g) <-100$ -> expensive Liquid Xenon (not a crystal)

Double beta decay

CaMoO4 sensitivity

•Ca,Mo purification, Active shield( 6cm CsI), Time correlation

(PSD), 5% FWHM assumed.•10kg Mo-100 enriched CaMoO4(100kg natural) Depleted Ca-48 or uses SrMoO4, PbMoO4 8x1024 years (0.2eV) <- explore Klopder’s claim

region. (Current best limit: 5x1022 years by Ejiri group)•10% Ca-48 enriched 10kg CaMoO4: 0 background, 1.5x1024 years (0.6eV) sensitivity (Current best limit : 2x1022 years)•1ton Mo-100 enriched CaMoO4 with further factor

100 background rejection. 8x1026 years (0.02eV) sensitivity <- next

generation goal.

CaMoO4 R&D

CaMoO4 crystal*5x5x5mm * 부산대

결정성장연구소

Pulse shape spectrum by Am-251 source

CaMoO4 and SrMoO4

S.B. Mikhrin et.al, NIMA 486 (2002) 295

1: SrMoO4

2: CaMoO4

Red-sensitive high efficiency silicon sensor

Large area AvalanchePhoto diode (1.6cm diameter)

4x4 1.5cm2 Photo diode

SummaryA R&D with HPGe, we already achieved world the

best limit for 2-, 0- Sn-124 excited level and Sn-122 transition.

With a pilot experiment with HPGe + Zn + CsI crystal, we ruled out Zn-64 EC++ positive evidence claimed by I.BIKIT et al. and set the limit to 2x1020 years by 95%CL .

Tin loaded LSC can be used for the double beta decay experiment. (up to 36% Sn loading

successful)

Crystal R&D of CaMoO4, ZnSe, GSO started for search with active detector technique.

ProspectNew 700m underground site at Yangyang : This will allow

us to compete with world wide dark matter & experiment.

1 liter enriched Sn loaded Liquid Scintillator: First Observation of 2 and T1/2 > 1022 years for 0 in Sn-124

10kg Mo-100 enriched CaMoO4 (SrMoO4, PbMoO4..) 8x1024 years (0.2eV) , 10% Ca-48 enriched 10kg CaMoO4: 1.5x1024 years (0.6eV) sensitivity

One ton Mo-100 enriched CaMoO4. 8x1026 years (0.02eV) sensitivity

Tl-208 (Q=5MeV) background

Mo-100 2+0 with 5% FWHM

candidates