Kaname HAMADA (Nagoya University) on behalf of the OPERA collaboration
Oscillation Project with Emulsion tRacking Apparatus
Status of the OPERA experiment
NEW TRENDS IN HIGH-ENERGY PHYSICS (CRIMEA 2011) 1
The goal of OPERA :
P() ~ sin2223cos413sin2(m223L/4E)P() ~ sin2223cos413sin2(m2
23L/4E)
Following the Super- Kamiokande observaion of oscillations with atmospheric neutrinos and the confirmation obtained with solar neutrinos and accelerator beams. Important, missing tile in the oscillation picture.
The PMNS 3-flavor oscillation formalism predicts:
Establish detection of neutrino oscillations in appearance mode through the channel.
Full mixing and m223 ~ 2.4 x 10-3 eV2
The light blue band indicates the OPERA allowed region (90% CL) for the above parameter values for 22.5 x 1019 pot
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oscillation
decay “kink”
~1 mm
-, h- ,e-
plus 3-prong decay modes
CC interaction
CC interaction
Difference between CC and CC interaction
In order to detect , the nuclear emulsion is used in a hybrid apparatus.Emulsion record charged particles as 3D tracks, and it has sub-micron resolution.
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BelgiumULB Brussels
CroatiaIRB Zagreb
FranceLAPP AnnecyIPNL LyonIPHC Strasbourg
GermanyHamburg
ItalyBariBolognaLNF FrascatiL’Aquila,LNGSNaplesPadovaRomeSalerno
JapanAichiTohoKobeNagoyaUtsunomiya
IsraelTechnion Haifa
KoreaJinju
RussiaINR RAS MoscowLPI RAS MoscowITEP MoscowSINP MSU MoscowJINR Dubna
SwitzerlandBernETH Zurich
TurkeyMETU Ankara
The OPERA Collaboration160 physicists, 30 institutions, 11 countries
http://operaweb.lngs.infn.it/4
LNGS
732km
CERNSPS
CNGS beam
1,400m underground
conventional beam
* Interaction rate at LNGS
< E > ( GeV ) 17 (e + e) / 0.87 %* / 2.1 %* prompt Negligible*
Expected interactions for 22.5x1019 pot (nominal pot in 5 years for 1.25kton target):
~23600 CC + NC ~160 e + e CC ~115 CC (m2 = 2.5 x 10-3 eV2)
~8 CC identified (BG<1)
L = 732 kmCERNLNGS
Tflight = 2.44 ms
5
50 micron
Microscopic imageRecorded as silver grains along the line where a charged particle passed through
Resolution : 0.3 m
OPERA emulsion film
Lead plate : 1mm
12.5cm
10cm
7.5cm
8.3kg10X0
Neutrino Beam(vertical for films)
Emulsion Cloud Chamber (ECC)
Stack of57 OPERA emulsion films,56 lead plates (10X0)
OPERA target – ECC brick –
horizontal track
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12.5cm
10cm
OPERA emulsion film
ECC + Target Tracker
Muon spectrometer
ECC + Target Tracker
Muon spectrometer
~1.25kton
OPERA detectorside view
150,000 ECC
~20 m
zoom in
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Scintillator Strips Target Tracker and brick trays
5 p.e. for a m.i.p.~ 99% detection efficiency trigger Position accuracy: ~ 8 mm brick location Probability map of event location in bricks
Module: 64 6-m scintillator stripsSignal transmitted by WLS fibersRead at both ends by 64-PMT
Brick trays: only 0.5% of target mass
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Magnetic Spectrometers: muon ID and momentum
• Dipole magnet
• 1.52 T magnetic field bending particles in the horizontal plane
• 24 slabs of magnetized iron interleaved with 24 RPC planes
• 6 drift tube stations for precision measurement of the angular deflection
• Momentum resolution: 20% below 30 GeV
Muon ID essential to reject Charmed particles background in CC interactions
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1010
20 m
top view
side view
top view
side view
charged current like
Neutral current like
Typical CC-likeand NC-like events
ECC brick extraction
ECC brick tagging by electronic detector11
1mm Pb
Primaryvertex
Decay point
Long flight decay
IP
1mm Pb
Primaryvertex
Decay point
Short flight decay
IP
charged current interaction in ECC
(Mean 104.3 m)
Kink → e- 17.8 %
→ μ- 17.4 %
→ h- 49.5 %
Trident → h- h- h+ 15.2 %
decay topology
Events with IP>10m are visually inspected: possible decay topologies
lifetime is short (c = 87m)
events (MC) NC+CC events (MC)NC+CC events (Data)
decay in same Pb plate
decay in further downstream Pb plate
Impact Parameter distribution
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Scanning speed/system: 75cm2/h*High speed CCD camera (3 kHz)*Piezo-controlled objective lens*FPGA Hard-coded algorithms
European Scanning System (ESS)Japanese Scanning System (S-UTS)
Scanning speed/system: 20cm2/h
*Customized commercial Optics and mechanics*Asynchronous DAQ software
5 systems in Japan 33 systems in Europe
Emulsion data taking – automatic scanning system –
ECC brick Scan & analysis JP : EU = 50:50
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ECC
Large area ~100 cm2
Point scan~100x100 m2
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
Lead
emulsion
emulsion
emulsion
neutrino
CS TThit
TThit
Ver
tex
plat
e
Follow back in brick tracks found in CS until they disappear: vertex plate
Interactions location in ECC brick
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1 cm
Scan about 10 films around vertex plate, and reconstruct tracks over several films.
Track reconstruction in ECC brick
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1 cm
Reject passing-through tracks and tracks connected in few films.
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1 cm
Search tracks making vertex by neutrino interaction.
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Momentum measurement
ECC featureParticle ID
Measurement of the position or angular displacement caused by the multiple Coulomb scattering
dRMS 13.6
pczx
X0
1 0.038lnx
X0
Particle ID is possible in ECC by dE/dx. (hadron or muon or electron)
Soft muon data sampleMuon momenta measured by MCS as a function of the momenta obtained from the electronic detectors.
The relative difference between the two measurements with respect to the electronic detector measurement.
Compatible ! 18
CNGS beamSummary of the 4 physics runs
Year Beam days Protons on target
Events in the bricks
2008 123 1.78x1019 1698
2009 155 3.52x1019 3693
2010 187 4.04x1019 4248
2011 Ongoing 3.31x1019 3304
As of 20 Aug. 2011
Goal of the experiment: 22.5x1019 pot
Total: 12.65x10 19 pot
2010
2009
2008
Days
pot2011
19
Global performance
Decay Search completed
Interactions located in the ECC bricks
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1st candidate event
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2
1
3
2
75
1
6
8 (daughter)
4 (candidate)
beam
track # tan x tan y p [GeV/c]
1 0.176 0.363 0.78 +0.13-0.10
2 -0.650 0.000 0.32 +0.31-0.11
3 0.108 0.113 1.97 +0.33-0.25
4( parent) -0.027 0.022
5 0.157 0.267 1.30 +0.22-0.16
6 0.334 -0.584 0.36 +0.18-0.09
7(from neutral particle)
0.438 0.419 0.49 +0.29--0.13
8( daughter) -0.007 -0.014 12 +6
-3
1 radiation length0.033 interaction length
top
view
side
vie
w
The viewer of scintillation Target Tracker
beam
primary vertex
kink point
interaction ECC -> pink color
Event topological features (Side view)・ 1-prong hadronic mode topology
・ IP = 55 ± 4 [m] (long flight decay)
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primary vertex
kink point
Pointing resolution (1) for a given gamma:
function of scattering and distance
attachment to the vertices
Distance from 2ry vertex (mm)
IP to 1ry vertex (m)<resolution>
IP to 2ry vertex (m)<resolution>
Prob. of attach. to 1ry vtx*
Prob. of attach. to 2ry vtx*
Attachment hypothesis
1st 2.2 45.0 <11> 7.5 <7> <10-3 0.32 2ry vertex
2nd 12.6 85.6 <56> 22 <50> 0.10 0.82 2ry vertex (favored)
* probability to find an IP larger than the observed one
The invariant mass of 1 2 is consistent with 0.The invariant mass of 1 2 and (daughter) is consistent with
daughter
120 ± 20 ± 35 MeV 640 +125-80
+100-90 MeV
Invariant mass reconstruction
with a B.R. of 25% )23
VARIABLE MeasuredSelection
criteria
Kink (mrad) 41 ± 2 >20
Decay length (m) 1335 ± 35 Within 2 plates
P daughter (GeV/c) 12 +6-3 >2
PT daughter (MeV/c) 470 +230-120
>300 ( attached)
Missing PT (MeV/c) 570 +320-170 <1000
ϕ (deg) 173 ± 2 >90
Kinematical variables
Satisfying all selection criteria for hadronic kink 1st candidate !
1 and 2 are both assumed as attached to 2ry vertex The uncertainty on PT due to the alternative attachment is < 50 MeV
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- Charged charmed particles have lifetimes similar to that of the lepton and share analogous decay topologies.
- The finding efficiecy of the decay vertices is therefore also similar for both types of particles.
- Comparing the observed charm event sample in size, decay topologies and kinematics with expectations from simulations is thus a straightforward way to verify that prompt-decay selection criteria and their corresponding efficiencies and backgrounds are well understood.
Finding efficiency of the charged charmed particles
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Charmed particle analysis with the 2008-2009 sample
Background sources for interaction
- Interactions of hadrons produced in interactions
- Decay of charmed particles produced in interactions
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1mm Pb
Decay
1mm Pb
NC interaction
re-interactionh
CC interaction
signal
BG Kinematical cut- “daughter” momentum (p) > 2 GeV/c- “daughter” transverse momentum (PT) > 0.6 GeV/c ( If gamma attached: PT > 0.3 GeV/c )
“daughter”
daughter
signal, BG separation
Hadron re-interaction background
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Hadronic tracks in neutrino interactions with
Kink topology far from primary vertexHadronic interactions in test beam brick
14 m, equivalent to 2300 NC events
Pion interaction studies
signal region signal region
No events found in the signal region.
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,e
-, e-
+e+
h+D+
-e-
h-
CC interaction e CC interaction
Charmed particles have similar decay topologies to the
primary lepton not identified
• Charm production in CC events represents a background source to all tau decay channels• This background can be suppressed by identifying the primary lepton
Charmed particles background
signal BG
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Summary of the backgrounds
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Signal events
One candidate event observed in the hadronic decay mode, with a BG of 0.05 +- 0.01 events. (0.49 +- 0.12 expected signal events)
For standard oscillation parameter values this corresponds to 95% probability that the event is not due to a BG fluctuation.
Considering all decay modes:expected 1.65 +- 0.41 events, BG = 0.16 +- 0.03 events.Probability of BG fluctuation: 15%
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An example of e candidate events
- 14 events in the analyzed sample- Developing dedicated analysis to increase the detection efficiency- Estimation of BG in progress: prompt e beam component and conversion contamination- - e oscillation analysis in progress
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- The goal of OPERA: Establish detection of neutrino oscillations in appearance mode through the channel, the signature being the identification of the lepton produced in its charged current interaction.
- In order to detect the appearance of though the identification of the lepton produced in their CC interactions, a massive hybrid detector is used where the required m spatial resolution is provided by emulsion films.
- We observed 1st candidate event in last year.
- After the observation of a 1st candidate event, OPERA is progressing with the analysis of new data.
- Our goal is to collect by the end of 2012 a total statistics (2008-2012) as close as possible to the goal of the experiment, namely 22.5x1019 p.o.t.
- In the analysed sample, expected signal = 1.65 +- 0.41 events, BG = 0.16 +- 0.03 events. - e oscillation analysis in progress.
Summary
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