M. Dracos, CEA, 10/04/2008 1

Double Beta experiment Double Beta experiment with emulsions?with emulsions?

ν =?

ν

M. Dracos, CEA, 10/04/2008 2

Double Beta DecayDouble Beta Decay

?

T 1/2 ~ 1019-1020 years !

Observed for: Mo100, Ge76, Se82, Cd116, Te130, Zr96, Ca48, Nd150

allowed double beta

double beta without neutrino

dW-

W-d

u

e-

e-

u

ν_

ν_

dW-

W-d

u

e-

e-

u

ν_

ν

Isotope Q(keV)

116Cd116Sn 2804.74.282Se82Kr 2995.23.3100Mo100Ru 3034.86.396Zr96Mo 3350.03.5150Nd150Sm 3367.14.948Ca48Ti 4272.04.1

The NEMO3 experimentThe NEMO3 experiment

M. Dracos, CEA, 10/04/2008 3

The NEMO3 detectorThe NEMO3 detector

Sources : 10 kg, 20 m2

wire chamber(Geiger)

3m

energy and time of flight measurements

plastic scintillator blocks

2 electron tracks

+photomultipliers (Hamamatsu 3", 5")

expected sensitivity up to mν~0.3 eV

M. Dracos, CEA, 10/04/2008 4

Event ExamplesEvent Examples

M. Dracos, CEA, 10/04/2008 5

ResultsResults932 g

389 days2750 even.

S/B = 4

82Se

82Se T1/2 = 9.6 0.3 (stat) 1.0 (syst) 1019 y

116Cd T1/2 = 2.8 0.1 (stat) 0.3 (syst) 1019 y

150Nd T1/2 = 9.7 0.7 (stat) 1.0 (syst) 1018 y

96Zr T1/2 = 2.0 0.3 (stat) 0.2 (syst) 1019 y

48Ca T1/2 = 3.9 0.7 (stat) 0.6 (syst) 1019 y

48Ca

background subtracted

Phase I + II693 days

T1/2(ν) > 5.8 1023 (90 % C.L.) <mν> <0.6-2.5 eV

Expected in 2009T1/2(ν) > 2 1024 (90 % C.L.) <mν> <0.3-1.3 eV

100Mo( 7 kg )

M. Dracos, CEA, 10/04/2008 6

Super NEMOSuper NEMO

• Improvements:– Energy resolution 15% E/E = 4% @ 3 MeV – Efficiency 15% 20 - 40% @ 3 MeV – Source x10 larger 7kg 100 - 200 kg

• Most promising isotopes– 82Se (baseline) or perhaps– 150Nd

• Aim: T1/2 > 2 x 1026 y M < 40 - 90 meV

R&D up to 2009, constructionbetween 2010 and 2013

source sheet

M. Dracos, CEA, 10/04/2008 7

e

e

22 with emulsions with emulsions

"veto" emulsion,if needed

(~50 m like in OPERA?)

plastic base

"2" emulsionthick enough to detect up to 4 MeV electrons (density?)

beta source(~50 m inNEMOcould be less for

emulsions)

M. Dracos, CEA, 10/04/2008 8

Tests in Nagoya using Tests in Nagoya using OPERA emulsionsOPERA emulsions

A. Ariga, diploma thesis

50 m

M. Dracos, CEA, 10/04/2008 9

22 with emulsions with emulsions1 MeV e-

2 MeV e-(Akitaka Ariga)

simulation

simulation

M. Dracos, CEA, 10/04/2008 10

22 with emulsions with emulsions

• NEMO3 surface: 20 m2

• Super-NEMO surface: 10x20 m2

• To cover the same isotope source surface with emulsions (both sides to detect the 2 electrons) we need an emulsion surface: 2x200=400 m2.

• Just for comparison, one OPERA emulsion has about 0.012 m2 and one brick 0.680 m2. So 400 m2 is about the equivalent of 600 OPERA bricks over 150000 (but not with the same thickness of course…).

• Use the same envelops like the OPERA changeable sheets by introducing at the middle of the two emulsions a double beta source sheet, or use longer emulsion sheets easier to handle by microscopes.

• Keep all these envelops for some time (e.g. 6-12 months depending on fading) in the experiment and after this period start scanning them one after the other. They could be replaced by new envelops during 5 years in order to accumulate something equivalent to what Super-NEMO could do: 400*5 year*m2

M. Dracos, CEA, 10/04/2008 11

0.003

0.003

0.1

0.11.2

7.0

4060

140

700

0.001

0.01

0.1

1

10

100

1000

cm

2 /

h

TS(1994) NTS(1996) UTS(1998) SUTS(2006) SUTS(2007-)

Scanning Power Roadmap

1stage

facility

CHORUS DONUT OPERA

22 with emulsions with emulsions• How much time is needed to make a full

scan of 2000 m2 (is a full scan in all volume really needed?)?

• If the Japanese S-UTS scanning system is used with a speed of 50 cm2/hour (be careful with thickness…), for one scanning table: 25 m2/year (200 working days/year). By using 16 tables and extracting 100 m2/3 months (1 year exposure at the beginning and putting back new emulsions with the same isotopes), this finally will take less than 5 years (as Super-NEMO).

• Probably the emulsion thickness needed to detect these electrons will need more scanning time and the speed would be significantly less than 50 cm2/h. On the other hand, scanning speed increases with time…

Nakamura sanNufact07

M. Dracos, CEA, 10/04/2008 12

Pending questionsPending questions• Energy resolution for NEMO: 15% for 3 MeV electrons

• Required for Super-NEMO: lower than 7% (goal 4%)

• Emulsion experiment energy resolution: ??? (monoenergetic 1 MeV 207Bi electrons could be used to have a good estimate of this resolution)

• Reconstruction efficiency for NEMO: 15%

• Required for Super-NEMO: 40%

• Emulsion experiment reconstruction efficiency: ?? (here also a well calibrated 207Bi source or other sources could be used)

• Minimum electron energy (~1 MeV, 0.5 MeV for NEMO3?)

• Afforded background?

• Could magnetic field help (better momentum resolution or rejection)?

• Possibility to take thinner isotope sheets (60 m for NEMO3) and have better energy resolution (but also more scanning for the same isotope mass).

M. Dracos, CEA, 10/04/2008 13

Extra IdeasExtra Ideas

ee

decreasing density

(25 mm layers)

to minimize the emulsion thickness and better energy

resolution at the end of the track

e

e

emitter in powder (diluted in an emulsion layer)

better vertex and energy reconstruction ?

after discussion with Fuji engineers, all these ideas are possible!

M. Dracos, CEA, 10/04/2008 14

ENDEND

M. Dracos, CEA, 10/04/2008 15

22 with emulsions with emulsionsfor 400  m2/year and 400 m2 isotopes available

isotope block number

time (years) surface (m2) exposure time (years)

surface*time (m2*years)

1 1.00 100 1.00 100

2 1.25 100 1.25 125

3 1.50 100 1.50 150

4 1.75 100 1.75 175

1 2.00 100 1.00 100

2 2.25 100 1.00 100

3 2.50 100 1.00 100

4 2.75 100 1.00 100

1 3.00 100 1.00 100

2 3.25 100 1.00 100

3 3.50 100 1.00 100

4 3.75 100 1.00 100

total 3.75 1200 13.50 1350

M. Dracos, CEA, 10/04/2008 16Electron + N ’s 208Tl (E = 2.6 MeV)

Electron crossing > 4 MeV Neutron capture Electron + delay track (164 s) 214Bi 214Po 210Pb

Electron – positron pair B rejection

BACKGROUND EVENTS OBSERVED BY NEMO-3BACKGROUND EVENTS OBSERVED BY NEMO-3

M. Dracos, CEA, 10/04/2008 17

E1+E2= 2880 keV

Run 2220, event 136.604, May 11th 2003

track(delay = 70 s)214Po 210Pb

214Bi 214Po decay IN THE GAS

νν-like event due to Radon from the gas (NEMO3)-like event due to Radon from the gas (NEMO3)

M. Dracos, CEA, 10/04/2008 18

NEMO3NEMO3

Proportion of types of events in raw data:

Type of event Rate (mHz)

1 e, 0 600

1 e, N

150

ee pairs 110

Crossing e 80

event 5.4 mHz