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).

50 micron

Microscopic Image

Recorded as silver grains along the line particle passed through

Resolution of 0.3 micron

Sub micron resolution 3D tracking

Nuclear Emulsion is used

1947 (C.Powell et al.)

Discovery of .

1971 (K.Niu et al.) Charm particle is discovered in cosmic-ray (called X-particle).

2001 (K.Niwa et al.) The first observation of at Fermi-Lab.

2009 ? First direct observation of

oscillation appearance

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

• The detector is located on the CNGS (CERN Neutrinos to Gran Sasso) beam line at a distance from the neutrino source of 730km.• Δm23

2 = (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.

INFN Gran Sasso

CERN SPS

730km

Appearance

Underground Laboratory

conventional beam

　 ( m-2 / pot) 7.45x10-9

CC / pot / kton 5.44x10-17

< E > ( GeV ) 17 (e + e) / 　 　　　　　　　　　　　 0.85 % / 4.0 % prompt negligible

%7.1~27.1sin2sin 2322

232

E

LmP τμ　

ECC detector ~ 1.3kton

5

ECC (Emulsion Cloud Chamber)125mm

100mm

75.4mm

8.3kg10X0

Neutrino Beam

OPERA emulsion film

Lead plate : 1mm

210μm44μm

emulsionPlastic base

beam 1mm

Lead

OPERA film

57 emulsion films and 56 Pb plates piled up.

6

Kink e 18 ％ 17 ％ h 49 ％

Trident 3h (h h h) 15 ％

How to detect tau neutrino

Flight Length： 280um

DONUT event

1mm

Emulsion

DONUT : Iron 1mmOPERA : Lead 1mm

7

The OPERA Detector @ Gran Sasso(1400m underground)

Emulsion　　+Target　Tracker Muon

spectrometer

Emulsion - Electronic Detectors Hybrid Detector

Emulsion Detector (ECC brick)

1.25 kton = 150,000 ECC bricks

ECC10cm

2.6cm

12.5cm

Changeable　Sheet　(CS)

T T

8

Flow of Emulsion Analysis

1. Location

Emulsion analysis is performed in two main steps

2. Decay Search

Trigger on Electronic detector ↓Connection from Electronic Detector to Emulsion Detector ↓locating the neutrino interaction in Emulsion Detector

-

- (e-, h-, 3h)

hh

Searching for tau decay topology

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

The most probable ECC brick is tagged by Target Trackers

extraction

Only CS Developed →Scanning Check tracks from the interaction . half @ Gran Sasso, half @ Japan

CSECC

12

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

Changeable Sheet (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.

Roles of CS

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.

extraction

?

Ratio of erasing > 99%

OPERA film produced in Japan. All accumulated background tracks were erased by “Refreshing”@ the underground G.S. lab.

Refresh: keeping the emulsion films at highrelative humidity(98%) and high temperature(30deg C) for 3days.

Two filmsEasily detached

Non refresh

After refresh

13

Scanning speed/system: 75cm2/hHigh speed CCD camera (3 kHz)

Piezo-controlled objective lens

FPGA Hard-coded algorithms

Emulsion Data taking – automatic scanning system – European Scanning SystemJapanese Scanning System

Scanning speed/system: 20cm2/h

Customized commercialoptics and mechanics

asynchronous DAQ software

Nagoya: 4 systems (75cm2/h) 1 systems (20cm2/h) 5 sub systems (1cm2/h)

LNGS: 10 systems, Napoli: 5 systems Bern: 5 systems, Bari: 4 systems Salerno: 4 systems, Bologna: 4 systems Padova: 1 systems

Total 325cm2/h All system : 20cm2/h Total 660cm2/h

14

CS Analysis

Emulsion track data consists its position, its slope and its darkness.

A real track is selected by the 4-layercoincidence and then validated by its quality.

In automatic data selection, Track read out Efficiency ~ 75% S/N ~ 1/2

Number of event 1473

Check done 1440

Found @ CS 1110

Next Brick; now going on 330

Current Status of CS

OPERA film OPERA film

To kill BG, 4 hold coincidence !!

Now going on

15

ECC

Large　area　scan~100cm2

Point　Scan~100x100m2

Lead

emul

sion

Lead

emul

sion

Lead

emul

sion

Lead

emul

sion

Lead

emul

sion

Lead

emul

sion

Lead

emul

sion

emul

sion

emul

sion

neutrino

Flow of Location – ECC –

CS TT

16

y

z

beam

Event: 228913162Brick: 29373Type: CC

y

x

~1.3mm

An example of Found Neutrino Event (1)

17

beam

y

z

y

x

Event: 228425652Brick: 16263Type: CC

An example of Found Neutrino Event (2)

18

beam

y

z

y

x

Event: 228482662Brick: 53754Type: NC

An example of Found Neutrino Event (3)

19Now going on

Location Summary:Number of events identified (located) in ECC bricks under microscope

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 bricks119 678 797

Interaction is upstream wall 12 46 58

interactions in the

dead material4 17 21

(In 1690 events triggered by Scintilator Target Trackers)

’08 Run only

20

Decay Search – detect kink topology –

Short flight decay ： 60%IP > 5umMin_pt > 250Mev/c

IP ~60% of tau leptons decay in the same Lead plate with vertex.

Long　flight　decay　： 40%

θkink > 20mrad pt > 250Mev/c

~10% : In Film Decay~30% : Next Lead Decay

cτ = 87 micron

Kink detection track angle deference between tau and daughter

Kink detection minimum distance between daughter and vertex point

21

Minimum distance between pairs of tracks from neutrino interaction (data, P>1GeV/c)

Minimum distance [micron]

Decay Search:High resolution to identify the topology of decay

IP of a decay daughter of (Monte Carlo)

22

Physical value from ECC1.Momentum measurement by multiple coulomb scattering

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%

P(GeV/c)

23

Physical value from ECC2. Electromagnetic shower

MCData

)(E

4.0~

GeV

@ a few GeVEnergy determination by calorimetric method

Test exp. @ CERN (May2001)

24

Physical value from ECC3. Particle ID by dE/dX

Dar

knes

s

-- Darkness

dE

/dX

(M

eV g

-1cm

2 )Momentum(GeV/c)

Momentum-dE/dX

P

0.87 GeV/c

P

D

Entry 1063 tracks

Particle ID

In Emulsion,dE/dX is defined as darkness of track. = 0.98

= 0.54

25

Event# 234539244, Brick# 51248

A charm candidate (1)

Kink angle = 209mrad

Flight Length= 1330micron

Decay Pt ~ 460MeV/c

1ry muon

Charm

1ry VTX is PL33. (100960, 52357)

depth=380micron up of film.

6 tracks found @ PL33.

CharmFlight length : 1330micron.Decay: in Lead (PL33-PL32 ) 340micron up of PL32.Kink angle : 209mrad.

Daughter Particle : muon (~2.2GeV)IP : 262micron.Decay Pt : ~ 460MeV/c

ax ay IP 1. 0.1325 0.0624 (PL33) 6.6 proton 2. 0.0097 -0.0663 (PL33) 4.5 3. 0.0876 0.6656 (PL33) 2.3 1ry mu 4. -0.0390 -0.1354 (PL33) 1.4 charm 5. 0.2215 0.4319 (PL33) 10.3 6. -0.0876 0.0418 (PL31) 18.9 e-pair 7. 0.0893 -0.0638 (PL33) 4.3

mu+

26

A charm candidate (2)A charm candidate (2)

Flight length 3247.2 μmkink 0.204 radPdaughter 3.9 (+1.7 -0.9) GeVPT 796 MeV

4x10-4 % probability for a hadron re-interaction to have a PT > 600 MeV

side

face

pl50 pl51 pl52 pl53 pl54 pl 55 pl 56 pl57

Clear kink topology Two EM showers pointing to the vertex

7

27

A Charm candidate (3)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. 4300 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