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, 23) 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, 2R&D with Crystals. 6) Prospect
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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.
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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
* 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%
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
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