Nasim Fatemi-Ghomi

1 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

Nasim Fatemi-Ghomi

Double Beta Decay Study of 150Nd

2 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

Introduction

Data Selection

• Data taking time =422.665 days = 1.16 yr - 348.036 days=0.95 yr (status=1) Dubna-2006 - 74.629 days=0.21 yr (status!=1)

• Events should come from Nd2O3. The foil has 57g mass (37g pure 150Nd).

Analysis toolAnalysis tool

Used UCL OO framework written by V.Vasiliev.Used UCL OO framework written by V.Vasiliev.

3 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

Internal BackgroundInternal Background

Bg Act(mBq/kg) Ge measurement

Modane-Baksan

Found from 1e channel

210Bi 368.42 -

207Tl 163.0 -

211Pb 163.0 -

234mPa 84.4 -

Found from eChannel

207Bi 235 128 - 120

Found from e + 214Bi 15.3 < 3 - 20

V.Tretyak(Aussois 2005)

40K 66.7 < 6.6 - 9.6

V.Vasiliev (Dubna 2004)

208Tl 7.95 9.6 - 5

228Ac 22.1 20 - 15

212Bi 22.1 -

Ge measurement

152Eu 38.3(modane) 21.6(Baksan)

External Background &External Background & Background on the SurfaceBackground on the Surface of the Wires and Foils.of the Wires and Foils.

Bg Act(Bq)

SW 214Bi 0.623

SW 214Pb 0.623

SF 214Bi 0.0185

SF 214Pb 0.0185

PM 214Bi 374

PM 214Pb 374

PM 228Ac 515

PM 60Co 50.7

PM 40K 954

Air 214Pb 702

Air 214Bi 702

Found byFound byV.Vasilev V.Vasilev checkedcheckedwith Cu foilwith Cu foil

4 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

Pre-selection for Pre-selection for 150150Nd to 2Nd to 2 events: events:

•Two negatively charged tracks associated with isolated PMTs and • E1 ,E2 > 0.2 MeV.• Both electrons originate from a common vertex • with |∆r| < 2 cm & |∆z| < 4 cm.• Internal TOF hypothesis > 4% & external TOF hypothesis < 1%.• Track starts from layers 1 & 2 of GG.• No delayed alpha decay with refiring time > 70 s.• No single or group delayed hit(s).

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1.11e-191.11e-19

150150Nd Half-life (with Status ==1)Nd Half-life (with Status ==1)

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150150Nd Half-life (status !=1)Nd Half-life (status !=1)

• Problems with PMs during runs (status 2 &10). Problems with PMs during runs (status 2 &10). 83 events83 events

• Problems with Geigers during run (status 3 &100). Problems with Geigers during run (status 3 &100). 12 events12 events

• Less than ~24 hours after absolute calibration (status 4 & 1000). Less than ~24 hours after absolute calibration (status 4 & 1000). 27 events27 events

• Less than ~24 hours after general HV shutdown (status 5 &10000) / less than ~24 Less than ~24 hours after general HV shutdown (status 5 &10000) / less than ~24 hours after HV shutdown of 1HV board (status 20000). hours after HV shutdown of 1HV board (status 20000). 51 events51 events

• Problems with ventilation, high radon rate (status 6&100000). Problems with ventilation, high radon rate (status 6&100000). 15 events 15 events

• No laser run for day correction (status 1000000) No laser run for day correction (status 1000000) 28 events28 events

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Combined good and bad runsCombined good and bad runs

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Good data:Number of data events: 1055Number of total background: 315Efficiency: 6.75%

T12= 9.23 -0.40+0.43(stat) 0.82(syst) x 1018 y

Half-life result for good and bad data.Half-life result for good and bad data.

Bad data:Bad data:Number of data events: 216 Number of data events: 216 Number of total background: 78Number of total background: 78Efficiency: 6.70%Efficiency: 6.70%

T12= 10.5 -1.0+1.3(stat) 0.96(syst) x 1018 y

The results are consistent The results are consistent Can combine the data Can combine the data

10 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

Half-life result for the combined dataHalf-life result for the combined data

T12= 9.46 -0.37+0.41(stat) 0.85(syst) x 1018 y

Number of data events: 1271Number of total background: 412Efficiency 6.74%

11 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

Preliminary 0Preliminary 0 result using MCLIMIT result using MCLIMIT

Number of generated 0Number of generated 0 = 50000 = 50000Number of accepted events = 3943Number of accepted events = 3943Using 1-dim histogram: Using 1-dim histogram: Esum for all energy regions (E1+E2>0.4 MeV)Esum for all energy regions (E1+E2>0.4 MeV)

Limit on half-life with 90% CL:Limit on half-life with 90% CL:

T120 >2.73 x 1020 y

12 Nasim Fatemi-Ghomi, Jaca meeting 5-8 December 2006

SummarySummary

• Half-life was extracted for good data and bad data Half-life was extracted for good data and bad data separately and the result for the half-life was consistent.separately and the result for the half-life was consistent.• The half-life was extracted for the combined data.The half-life was extracted for the combined data.• Avery preliminary result on limit on Avery preliminary result on limit on T12

0 was was

presented.presented.• Have to start working with Phase II Data!!Have to start working with Phase II Data!! + + • The first draft of a technical note on The first draft of a technical note on 150Nd2 (phaseI) analysis is written!