the opera experiment 12 th topical seminar on innovative particle and radiation detectors (iprd10)...
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The OPERA Experiment 12th Topical Seminar on Innovative Particle and Radiation Detectors
(IPRD10)
7-10 June 2010, Siena, Italy
Jonas Knüsel
Albert Einstein Center for Fundamental PhysicsLaboratory for High Energy Physics
University of BerneOn behalf of the OPERA collaboration
The Photographic Emulsion Technology of the OPERA Experiment on its Way to
Find the →
Oscillation
OPERA
Oscillation Project with Emulsion tRacking Apparatus
JINST 4 (2009) P06020
New Journal of Physics (2006) 303a
JINST 4 (2009) P06020
• Introduction
• The OPERA experiment
• The nuclear emulsion technology
• On the way to find the →
oscillation
• Conclusion
4
IntroductionThe OPERA collaboration
LAPP AnnecyIPNL LyonIPHC Strasbourg
INR, LPI, ITEP, SINP MoscowJINR Dubna
IRB Zagreb
BariBologna L’AquilaLNF FrascatiLNGSNapoliPadovaRomaSalerno
BernETH Zurich
ULB Brussels HamburgMünsterRostock
AichiTohoKobeNagoyaUtsunomiya
Technion HaifaMETU Ankara
Jinju
• 33 Institutions
• ~200 physicist
IntroductionPhysics motivation
• Neutrinos as fundamental particles of the SM
• Flavour vs. Mass Eigenstates:
– Mixing – Oscillation!
• Oscillation parameters: θ and ∆m2, available in experiment: L, E
• Detection of Tau Neutrino from an oscillated muon neutrino via the tau decay kink.
– High target mass to compensate low neutrino cross section: use LEAD
– High granularity and resolution to see the tau kink: use PHOTGRAPHIC EMULSIONS
• Prove neutrino oscillation by observing the Tau appearance.
IntroductionPrinciple of topological detection
Topology Selection
τ-ν
μ, e, h, 3h
h
h
cτ = 87 micron
Tau decay kinkAlso other topologies, according to decay:
νt
νt
<Enm> 17 GeV
L 730 km
(ne+ne)/nm CC 0.87%
nm/n m CC 2.1%
nt prompt negligible
The OPERA experimentFrom CERN to Gran Sasso
CERN
LNGS
730 km
Expected number of interactions in 5 years running:
~23600 nm CC + NC~205 ne + ne CC
~115 nt CC (Dm2=2.5 x 10-3 eV2)
~ 10 tau decays are expected to be observed, with less than 1
background event
8
The OPERA experimentThe OPERA detector
Dimension of the detector: 20m x 10m x 10m
The OPERA experimentThe OPERA detector
Brick Wall and Brick Manipulation system.bricks
scintillator
The OPERA experimentThe OPERA basic unit: the „brick“
125mm
100mm
75.4mm
8.3kg10X0
Neutrino
Beam
OPERA emulsion film
Lead plate : 1mm
The Emulsion Cloud Chamber (ECC)
• The OPERA emulsion film plays the main role in this experiment.
• These emulsion films are scanned by automatic optical microscopes.
• > 200000 m2 of emulsion surface in OPERA
57 emulsion per brick
CSd
The OPERA experimentThe scanning systems
• Scanning speed/system: 75cm2/h• High speed CCD camera (3 kHz) , Piezo-
controlled objective lens• FPGA Hard-coded algorithms• Japan overall capacity: ~ 200 cm2/h
• Scanning speed/system: 20cm2/h • Customized commercial optics and
mechanics• Asynchronous DAQ software• EU overall capacity: ~ 200 cm2/h
JapanEurope
ESS: (European Scanning System) SUTS (Super Ultra Track Selector)
The OPERA experimentThe scanning procedure
1257565554535251504948…21
CSdScanback• Track follow-up film by film:
• Alignment using cosmic ray tracks
• Definition of the stopping point
Volume-Scan• Volume scanning (2-3 cm2)
around the stopping point
The OPERA experimentThe scanning analysis
JINST 4 (2009) P04018
Different steps of the emulsion data processing
• All base-tracks in the 11 films
• Long tracks for the alignment
• Tracks belonging to the vertex
≈ 2 mm
Position residuals for the position alignment
The OPERA experimentFrom the m to the m scale
• Detector• Muon Spectrometer
O (m)
The OPERA experimentFrom the m to the m scale
• The ECC brick
O (m)O (cm)
extraction
The OPERA experimentFrom the m to the m scale
• The Changeable Sheet (CS)
O (m)O (cm)O (mm)
JINST 3 (2008) P07005
CS:2 emulsion film
located on the brick
The OPERA experimentFrom the m to the m scale
O (m)O (cm)O (mm)
emulsion film doublets
• CS confirmes prediction by electronic detectors.• Move from cm-range (electronic detector) to mm-range• Bricks are only developed after CS confirmes prediction
The OPERA experimentFrom the m to the m scale
O (m)O (cm)O (mm)O (mm)
• The emulsion
This is the main part of the OPERA experiment. The essentiall stuff happens here. Vertex finding and topology classification.
1 cm
1 cm
The nuclear emulsion technologyRenaissance
The central part of OPERA happens in emulsion films:
• AgBr Crystal, size ~ 0.2 microns
• Semiconductor detector technique, band gap ~ 2.6eV
• Signal amplified by developing the photographic films.
• After developing the „silver grains“ are read out by optical microscopes
Plastic Base (205micron)
Emulsion Layer
Emulsion Layer (44micron)
The nuclear emulsion technologySub micron resolution 3D tracking
50 micron
Microscopic Image
Recorded as silver grains along the line particle passed through
Resolution of 0.3 micron
cτ of tau:
~87 microns
The nuclear emulsion technologyMicroscope images
JINST 4 (2009) 6020
Nuclear emulsion image as seen by the microscope
Peculiar event: neutrino interaction occured inside the emulsion layer
On the way to find the nm→ nt oscillation
First OPERA run 2006
• Only electronic detectors, at that time:• No bricks in target, then.
Cosmic muon induced background
Muons from CNGS beam.Angle w.r.t. earth curvature: 3.4 degree.
New Journal of Physics 8 (2006) 303
✔ Neutrino beam✔ Electronic detector
24
On the way to find the nm→ nt oscillation
nm CC interaction
muon primary vertex 4 tracks with IP < 2 mm
secondary vertex 2 tracks with IP < 4 mm
2.2 cm
7 mm
25
y
On the way to find the nm→ nt oscillation
nm CC interaction
muon primary vertex 4 tracks with IP < 2 mm
6 Gammas reconstructed4 Gammas from 1ry vtx2 Gammas from 2ry vtx
secondary vertex 2 tracks with IP < 4 mm
2.2 cm
7 mm
On the way to find the nm→ nt oscillation
Charm candidates
• Thetakink: 0.204 rad• Pdaughter: 3.9 (+1.7 -0.9) GeV• PT: 800 MeV
• Flight length: 3247.2 μm • 2 EM-showers point to
vertex
Charm topology analogous to tau (similar lifetime): reference sample for the decay finding efficiency
On the way to find the nm→ nt oscillation
Charm candidates
Event in Europe (D0 4 prong) Event in Japan (kink)
Topology Kink Vee Trident 4Vee
Observed events 5+2N1 5 1+N3 1
On the way to find the nm→ nt oscillation
ne interaction
6 ne interactions found in a subsample of 690 CC located interaction (expected are about 6)
On the way to find the nm→ nt oscillation
search for t
• Search for nt is ongoing
• Systematic decay studies are performed for all interactions
• About 2 t are expected from 2008-2009 run
Channel Signal Background
t → m 2.9 0.17t → e 3.5 0.17
t → h 3.1 0.24t → 3h 0.9 0.17
Total 10.4 0.75
On the way to find the nm→ nt oscillation
work in progress...
• CNGS run 2010 is going well (started on April 20th 2010)
• Continuous extraction of bricks from triggered events
• About 100 bricks / week are extracted, developed and sent to the labs
• Systematic decay search studies are performed to find all possible decay topologies.
Conclusion
• OPERA, the largest nuclear emulsion experiment is successfully taking data.
• OPERA has collected for 5.3E19 pot in 2008 and 2009.
• The full chain of events handling/analysis is proven.
• Electronic detector performance is reliable and well understood.
• Several charm events are found as expected.
• The first t event is close...
Additional Information2008 run status (May 5th, 2010)
0mu 1mu All
Events predicted by the electronic detector 406 1292 1698
Found in CS 276 1056 1332
Neutrino interactions in the bricks 155 798 953
Located in dead material 8 40 48
Interaction in the upstream brick 6 35 41
Decay search completed 130 673 803
• Decay search completed for 84.3% of the sample
• 22 observed charm candidates
• Decay search completed for 42.1% of the located event sample
• 4 observed charm candidates
0mu 1mu All
Events predicted by the electronic detector 1097 2460 3557
Events with at least 1 brick extracted 1050 2389 3439
CS scanned 826 2143 2969
Found in CS 447 1418 1865
Neutrino interactions in the bricks 112 550 662
Located in dead material 3 15 18
Interactions in the upstream brick 4 50 54
Decay search completed 53 226 279
Additional Information2009 run status (May 5th, 2010)
