Comments on OPERA

• OPERA is going on. We will have good Tau neutrino interactions within years, if νμ － ντ oscillation is the real solution.

• New Techniques developed in OPERA Very fast Read out system SUTS, Emulsion film with new AgBr crystals Low energy electron detection

MeV Energy electron signal in OPERA

• CS1-CS2 alignment using Compton electrons. Very good track connection between two emulsion layers

σ ～ 1.8μm

By S. Miyamoto

Δｙ

Δｙ

Double Beta decay detection by Nuclear Emulsion

• Neutrino less Double Beta Decay

　　 1) Two electrons emitted from one point.

Micron accuracy measurement

Chance coincidence rejection by the position measurement

　　 2) Total energy

Tracking Calorimeter:

Track length + Grain information

(Z,A)→(Z+2,A) + e1- + e2

- + νe1 + νe2 (Z,A)→(Z+2,A) + e1

- + e2-

Emulsion

Emulsion

Source

Set-up example

Basic Element :

ECC configuration

Source layer+ Emulsion layers

(100Mo foil for example)

Source (Foil) 10micron

50 micron emulsion layer on both sides of the foil.

1 Unit

Set-up example NEMO3 level Next generation

Source mass 10kg 100kg

Emulsion Amount 10 litter 100 litter

(FNAL E531 level) (CHORUS level)

Scanning load 200 days OPERA SUTS Need X10 faster system !

20cm

20cm

25cm

50cm

50cm

45cm

2500 unit 4500 unit

Main Background : 214Bi ,208Tl (Max 3.17MeV beta) comes from Rn or contained U, Th chains.

Those can be rejected by the existence of Alpha particles easy in Emulsion

About BackgroundNEMO3 NEMO3

                                        

理科年表（丸善）

10μm

βray

α ray track.

Uranium Chain

Thorium Chain

α decay

βdecay

Chain Products(Alpha and Beta) are contained within several micron^3

Summary• OPERA is going on. R&D in OPERA Applications (Double Beta, Directional Dark Matter detection etc)

Compact Double beta experiment with nuclear emulsion is possible.

Current main background from Th ・ U chain can be rejected by detecting the existence of αrays.

In the case of Emulsion..In the emulsion, background caused by Th ・ U chain can be rejected by α ray track.

Βray of Th ・ U chain exist with α ray!

10μm

βray

Needed Mass of emulsion• 100Mo Status strongest limit T1/2

0ν > 1023 year

MoO3 sheet(10μm thickness)

enrichment of 100Mo 90% ⇒more than 1,000 kg emulsion (efficiency ～ 100% , 1year exp.)

• 150Nd Status strongest limit T1/2

0ν > 1021 year

NdO3 (10μm thickness)

enrichment of 150Nd 91% ⇒more than 1kg emulsion (efficiency ～ 100% , 1year exp.)

• 96Zr Status strongest limit T1/2

0ν > 1021 year ZrO2 (10μm thickness) enrichment of 96Zr 57%

⇒more than 100 kg emulsion (efficiency ～ 100% , 1year exp.)

Status Nuclear Emulsion experiment Emulsion mass : 30,000kg

Source material should be decided by relation between Q-value and background or compatibility with emulsion.

For example

energy resolutionAt least, E is about ⊿ 20% by effective range.

effective range

By trace of the one track, E is expected about ⊿ 10%

By developing the new emulsion of high sensitivity and having high AgBr density ( ex. Fine grain emulsion), pick up the some energy loss. (ionization, knock-on electro

n , Bremsstrahlung etc) ⇒ 　 aim to 5%

Low Energy electron signal

• CS1-CS2 alignment in OPERA( Compton Alignment)

By this technique, It is possible to detect the MeV electrons.

σΔx～ 2.1μm

σΔy～ 1.8μm

By S. Miyamoto

2νββ and 0νββ

p

p

e-ν

n

n

e-

ν

W+

W+

n

n

e-W+

W+ e-

p

p

νR=νR

(T1/22ν) -1=G2ν (Q,Z) |M2ν|2 (T1/2

0ν) -1=G0ν (Q,Z) |M0ν|2<mν>2

• Which is neutrino Majorana or Dirac particle?• How much is neutrino’s mass?• Investigation of Lepton Flavor Violation

Neutrino must be Majorana particle. ( ν 　 = ν ）

2νββ 0νββ

Enegy spectrum of double beta decay

(Z,A)→(Z+2,A) + e1- + e2

- + νe1 + νe2 (Z,A)→(Z+2,A) + e1

- + e2- Total energy of 2 electron is Q-value region of energy

spectrum of 2ν mode electrons.

S(0

ν)/

N(2

ν)Energy resolution [%]

The case of T1/2 0νββ

T1/2 2νββ～ 106

Energy resolution is very important to distinguish between 0νββ　 and 2νββ !!