1. The Nuclear Emulsion Technology and the Analysis of the OPERA Experiment Data
Tsutomu Fukuda
Nagoya University, JAPAN
On behalf of the OPERA Collaboration
DPF-APS 2009 , 28 JULY 2009, Wayne State University in Detroit

2. Nuclear Emulsion
Nuclear Emulsion is a special kind photographic film. : AgBr micro crystal semiconductor (Band gap ~ 2.6eV).
Signal is amplified by chemical process (developing).
Nuclear Emulsion is used (C.Powell et al.) Discovery of  (K.Niu et al.) Charm particle is discovered in cosmic-ray (called X-particle) (K.Niwa et al.) The first observation of    at Fermi-Lab.
50 micron
Microscopic Image
Recorded as silver grains
along the line particle passed through
Resolution of 0.3 micron
2009 ? First direct observation of   
oscillation appearance
Sub micron resolution 3D tracking

3. OPERA experiment
Theory: In 1962, Maki, Nakagawa and Sakata conceived massive neutrino will oscillate. Important experimental result (1): In 1998, Super-Kamiokande detected the behaviour of neutrino oscillation (atmospheric  disappearance). Important experimental result (2): In 2001, DONUT ( FermiLab experiment) succeeded in detecting  by Emulsion Cloud Chamber (ECC).
Goal:
The goal of OPERA is to detect  oscillated from  by ECC.

4. Conceptual Design   Appearance INFN Gran Sasso
CERN SPS
conventional  beam
　( m-2 / pot) x10-9
 CC / pot / kton x10-17
< E > ( GeV )
(e + e) /  　 %
 /  %
 prompt negligible
730km 
Appearance
ECC detector ~ 1.3kton
INFN Gran Sasso
Underground Laboratory
The detector is located on the CNGS (CERN Neutrinos to Gran Sasso) beam line at a distance from the neutrino source of 730km.
Δm232 = (2.43±0.13)×10-3 eV2 , sin22θ23 = 1.0
# of  events = 4300/year
expected detectable # of  CC events ~ 2.5/year
Here, I will mainly talk about Emulsion Technology and Analysis.

5. ECC (Emulsion Cloud Chamber)
125mm
100mm
75.4mm
8.3kg
10X0
Neutrino Beam
57 emulsion films and 56 Pb plates piled up.
OPERA emulsion film
Lead plate : 1mm
OPERA film
1mm
beam
44μm
210μm
Plastic base
emulsion
Lead

6. How to detect tau neutrino
DONUT  event
Flight Length：280um  
1mm
Emulsion
Kink
  e
18 ％
  
17 ％
  h
49 ％
Trident
  3h (h h h)
15 ％
DONUT : Iron 1mm OPERA : Lead 1mm

7. The OPERA Detector @ Gran Sasso(1400m underground)
Emulsion +
Target Tracker
Muon
spectrometer
Emulsion - Electronic Detectors Hybrid Detector
ECC
10cm
2.6cm
12.5cm
Changeable Sheet (CS)
T T
Emulsion Detector (ECC brick)
1.25 kton = 150,000 ECC bricks 

8. Flow of Emulsion Analysis
Emulsion analysis is performed in two main steps
Trigger on Electronic detector ↓ Connection from Electronic Detector to Emulsion Detector
↓ locating the neutrino interaction in Emulsion Detector
1. Location  
2. Decay Search  -
- (e-, h-, 3h)
Searching for tau decay topology h h

9. Vertex Location – trigger by electronic detectors –
CC-like (with muon)

10. Vertex Location – trigger by electronic detectors –
NC-like (no muon)

11. Vertex Location extraction  ECC CS Only CS Developed →Scanning
The most probable ECC brick is tagged
by Target Trackers 
ECC CS
Only CS Developed →Scanning
Check tracks from the interaction . Gran Sasso, Japan

12. Changeable Sheet (CS) ? Roles of CS
Two films
Easily detached
Roles of CS
Electronic detectors don’t have enough resolution to identify the ECC
Brick where the interaction has occurred. To identify the brick, CS is needed.
OPERA film produced in Japan. All accumulated background tracks were erased by the underground G.S. lab.
In the CS, only ν associated track
is recorded. If track is found at CS.  the daughter of ν interaction.  Emulsion film of ECC are developed In the case a track is NOT found  Next Brick should be taken out.
Refresh: keeping the emulsion films at high relative humidity(98%) and high temperature (30deg C) for 3days. ?
Non refresh
extraction
After refresh
Ratio of erasing > 99% 12

13. Emulsion Data taking – automatic scanning system –
Japanese Scanning System
European Scanning System
Scanning speed/system: 75cm2/h
High speed CCD camera (3 kHz)
Piezo-controlled objective lens
FPGA Hard-coded algorithms
Scanning speed/system: 20cm2/h
Customized commercial
optics and mechanics
asynchronous DAQ software
LNGS: 10 systems, Napoli: 5 systems
Bern: 5 systems, Bari: 4 systems
Salerno: 4 systems, Bologna: 4 systems
Padova: 1 systems
Nagoya: 4 systems (75cm2/h) systems (20cm2/h) sub systems (1cm2/h)
Total 325cm2/h
All system : 20cm2/h  Total 660cm2/h

14. Next Brick; now going on
CS Analysis
OPERA film
OPERA film
To kill BG, 4 hold coincidence !!
Emulsion track data consists its position, its slope and its darkness. A real track is selected by the 4-layer coincidence and then validated by its quality.
In automatic data selection,
Track read out Efficiency ~ 75%
S/N ~ 1/2
Current Status of CS
Number of event
1473
Check done
1440 CS
1110
Next Brick; now going on
330
Now going on

15. Flow of Location – ECC – ECC CS TT Large area scan~100cm2 Point Scan
~100x100mm2
neutrino
emulsion
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead 15

16. An example of Found Neutrino Event (1)
beam y z y x
~1.3mm
Event:
Brick: 29373
Type: CC

17. An example of Found Neutrino Event (2)
beam y z y x
Event:
Brick: 16263
Type: CC

18. An example of Found Neutrino Event (3)
beam y z y x
Event:
Brick: 53754
Type: NC

19. Location Summary: Number of events identified (located) in ECC bricks under microscope
’08 Run only NC CC
Total
Bricks received in labs
218
959
1177
Bricks measured
195
895
1090
CS to brick connection successful
178
849
1027
 interactions located
in the bricks
119
678
797
Interaction is upstream wall 12 46 58
 interactions in the
dead material 4 17 21
(In 1690 events triggered by Scintilator Target Trackers)
Now going on

20. Decay Search – detect kink topology –
Long flight decay ：40%
θkink > 20mrad pt > 250Mev/c q
~10% : In Film Decay ~30% : Next Lead Decay
cτ = 87 micron
Kink detection  track angle deference between tau and daughter
Short flight decay：60%
IP > 5um
Min_pt > 250Mev/c
~60% of tau leptons decay in the same Lead plate with vertex. IP
Kink detection  minimum distance between
daughter and vertex point

21. Decay Search: High resolution to identify the topology of  decay
Minimum distance between pairs of tracks from neutrino interaction
(data, P>1GeV/c)
IP of a decay daughter of  (Monte Carlo)
Minimum distance [micron]

22. Physical value from ECC 1
Physical value from ECC 1.Momentum measurement by multiple coulomb scattering
P(GeV/c)
P =
13.6 (MeV/c)  X0 x
1/P(GeV/c)-1
0.8GeV/c pion : P =0.79(GeV/c), dP/P =11%
1.5GeV/c pion : P =1.53(GeV/c), dP/P =16%

23. Physical value from ECC 2. Electromagnetic shower
Test CERN (May2001) MC
Data
@ a few GeV
Energy determination
by calorimetric method

24. Physical value from ECC 3. Particle ID by dE/dX
In Emulsion, dE/dX is defined as darkness of track.
 = 0.98
 = 0.54
 -- Darkness
Darkness
Momentum-dE/dX
0.87 GeV/c
Entry 1063 tracks  P
dE/dX (MeV g-1cm2) P   D
Particle ID
Momentum(GeV/c)

25. A charm candidate (1) Event# 234539244, Brick# 51248
1ry VTX is PL (100960, 52357)
depth=380micron up of film.
6 tracks PL33.
Charm Flight length : 1330micron. Decay: in Lead (PL33-PL32 ) micron up of PL32. Kink angle : 209mrad.
Daughter Particle : muon (~2.2GeV) IP : 262micron. Decay Pt : ~ 460MeV/c
Decay Pt ~ 460MeV/c
mu+
Kink angle
= 209mrad
Charm
ax ay IP
(PL33)  proton
(PL33)
(PL33)  1ry mu
(PL33)  charm
(PL33)
(PL31)  e-pair
(PL33)
Flight Length
= 1330micron
1ry muon

26. A charm candidate (2) side face Clear kink topology
pl50 pl51 pl pl pl54 pl pl pl57
side
face
Clear kink topology
Two EM showers pointing to the vertex
Flight length μm
kink rad
Pdaughter ( ) GeV
PT MeV
4x10-4 % probability for a hadron re-interaction to have a PT > 600 MeV 7

27. A Charm candidate (3)

28. Summary The goal of OPERA is to detect  oscillation appearance.
OPERA developed Nuclear Emulsion Technology.
In 2008 Run, 1690 neutrino events were triggered in the target tracker. 797 vertices were found in ECC bricks under microscope and the search is going on.
From the observation of charm candidates, the ability to detect kink or trident tau decay topologies is proven and its efficiency is being evaluated.
For the run of 2009 that started on June 1, we require 4.5E19 p.o.t neutrino events should be collected in ECC targets. About 2.5 tau-neutrino interactions are expected to be detected. By 5 years, OPERA will get 10  events.
The OPERA detector suffered no damage following the L’Aquila earthquake. Great thanks to you for the huge support from all over the world!

29. fin