Transcript opera

Status and results from
the OPERA experiment
Tsutomu FUKUDA ( Nagoya University )
On behalf of the OPERA Collaboration
NNN10 , 14 Dec 2010, Toyama International Conference Center in Toyama, JAPAN
Oscillation Project with
Emulsion-tRacking Apparatus
First direct detection of neutrino oscillations in
appearance mode through the  channel.
-


decay “kink”

oscillation

-

- ,h-,e-
~1 mm
Requirements : high neutrino energy & intensity
& long base line & large target mass
& detect short lived ’s
2 important experimental results
for OPERA design
Neutrino oscillation (disappearance)
Result from SK in 1998
Direct observation of  events
Result of DONuT in 2001
Flight Length：280um


1mm
Iron
DONuT  event
OPERA start !!
The OPERA Collaboration
180 physicists, 33 institutions in 12 countries
Belgium
Italy
IIHE-ULB Brussels
Bari
Bologna
LNF Frascati
L’Aquila
LNGS
Naples
Padova
Rome
Salerno
Croatia
IRB Zagreb
France
LAPP Annecy
IPNL Lyon
IPHC Strasbourg
Germany
Hamburg
Münster
Rostock
Israel
Technion Haifa
Russia
INR RAS Moscow
NPI RAS Moscow
ITEP Moscow
SINP MSU Moscow
JINR Dubna
Switzerland
Bern
ETH Zurich
Japan
Aichi
Toho
Kobe
Nagoya
Utsunomiya
Korea
Jinju
Tunisia
CNSTN Tunis
Turkey
METU Ankara
Our philosophy
following the Super- Kamiokande discovery of
oscillations with atmospheric neutrinos and the
confirmation obtained with solar neutrinos and
accelerator beams.
Important, missing tile in the oscillation
picture.
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
• OPERA give a clear and strong evidence for the existence of neutrino
oscillation.
• OPERA is also searching for first direct observation of Lepton Flavor
Violation.
CNGS beam line
conventional  beam
< E > ( GeV )
(e + e) / 
 / 
 prompt
CERN
17
0.87 %*
2.1 %*
Negligible*
* Interaction rate at LNGS
732km
LNGS
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)
~10 CC identified (BG<1)
The OPERA target – ECC brick –
Recorded as silver grains along the line
where a charged particle passed through
OPERA emulsion film
50 micron
Lead plate : 1mm
Resolution of 0.3 micron
Microscopic Image
75.4mm
125mm
8.3kg
10X0
Neutrino Beam
100mm
Emulsion Cloud Chamber (ECC)
57 OPERA films and
56 lead plates piled up.
The OPERA detector
Emulsion +
Target Tracker
Muon
spectrometer
Emulsion +
Target Tracker
Muon
spectrometer
OPERA emulsion film
Typical CC-like and NC-like events
 CC-like event
20 m
 NC-like event
Emulsion Scanning for CS
• CS Scan & analysis  NAGOYA : LNGS = 50:50

Changeable Sheets (CS), two OPERA films
fixed downstream of the ECC bricks, are
used as interfaces between the electronic
trackers and the ECC bricks.
ECC brick
CS
When a neutrino interaction is detected by
the electronic detectors, the most probable
brick is extracted and the CS are developed
and analyzed.
If one or more predicted tracks are found,
the brick films are developed. If not, the
brick is returned back to the detector with
new CS and the next brick is extracted.
By using CS, emulsion analysis speed
become about 10 times faster.
Emulsion Scanning for ECC brick
• ECC brick Scan & analysis  JP : EU = 50:50
After tracks are found on CS,
ECC brick films are developed
and sent to scanning labs
along with the CS information.
Bern
Padova
Bologna
Roma LNGS
LNF
Napoli
Salerno
Bari
Neutrino event location
CS
ECC brick
STOP

5 mm
CS  ~100cm2 large area scan
ECC  ~100100m2 point scan
How to locate
1. Connect track CS to ECC brick.
2. Follow up track in ECC brick.
(Scan Back method)
3. Confirm the stop plate.
4. Scan around stop plate.
The Plate changer system for
Scan Back in Japan.
Films of ECC brick are glued on
a sheet for changing plates easily.
Located neutrino interaction in ECC brick
Scan about 10 plates around stop plate by follow up from down stream.
1 cm

Located neutrino interaction in ECC brick
Reject passing trough track and only few plates connect track.
1 cm

Located neutrino interaction in ECC brick
Search tracks making vertex by neutrino interaction .
1 cm

Progress of CNGS runs
Year
Days
beam
POT
Events
Run
2006
0.076×1019
no bricks
Commissioning
2007
0.082×1019
38
Commissioning
2008
123
1.78×1019
1698
First physics
run
2009
155
3.52×1019
3693
Physics run
2010
187
4.04×1019
4248
Physics run
POT
2010
• POT of 2010: 90% of nominal year
2009
2008
• 9639 events collected (within 1s in
agreement with expectations from pot)
→ 2.1 nominal years in 3 years.
Days
Location Status
Interaction in the target
Events with at least 1 brick extracted
Events with a positive CS result
Interactions located in the bricks
Decay Search completed
• Event location is going well. 2779 events are already located.
• Based on the 2008 run efficiencies, about 5650 events to be located
in ( 2008 + 2009 + 2010 run ).
Decay topology search
IP distribution for
 events (MC)
Decay Pt ~ 460MeV/c
Kink angle
= 209mrad
+
Charm
Flight Length
= 1330micron
1ry 
IP distribution for:
 events (MC)
NC+CC  events (MC),
NC+CC  events (Data)
A Charm event (dimuon event)
In 901 sub-sample events,
20 charm events were found.
(expected : 16.0±2.9)
Event statistics for Decay search
The analysis of a sub-sample of the data
taken in the 2008-2009 runs was completed.
Number of events completed:
1088 (187 NC)
This is ~20% of the total 2008-2010 run statistics, corresponding to 1.85 x 1019 pot
With the above statistics, and for m223 = 2.5 x10-3 eV2 and full mixing, OPERA expects:
~ 0.5  events
The first  candidate event was found
Event number 9234119599,
taken on 22 August 2009, 19:27 (UTC)
This result is opened at June/2010.
Event topological features (Side view)
7
3
5
g2
1
kink point
primary
vertex
g1
2
4 ( cand)
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
track)
0.438
0.419
0.49 +0.29--0.13
8（daughter）
-0.007
-0.014
12 +6-3
1 radiation length
0.033 interaction length
The viewer of scintillation Target Tracker
top view
6
8 (daughter)
 beam
Event ECC  pink color
side view

γattachment to the vertices
Pointing resolution (1s) for a given
gamma: function of scattering and
distance
primary
vertex
g2
kink
point
g1
The invariant mass of g1 g2 is consistent with p0.
The invariant mass of g1 g2 and p-(8) is consistent
with r(770).
Distance
from 2ry
vertex (mm)
IP to 1ry
vertex (m)
<resolution>
g1g2
p-(8)g1g2
120 ± 20 ± 35 MeV
640 +125-80 +100-90 MeV
IP to 2ry
vertex (m)
<resolution>
Prob. of
attach. to
1ry vtx*
Prob. of
attach. to
2ry vtx*
Attachment
hypothesis
1st g
2.2
45.0 <11>
7.5 <7>
<10-3
0.32
2ry vertex
2nd g
12.6
85.6 <56>
22 <50>
0.10
0.82
2ry vertex (favored)
* probability to find an IP larger than the observed one
Kinematical variables
(Animation)
VARIABLE
Measured
Selection
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
(g attached)
Missing Pt
(MeV/c)
570 +320-170
<1000
ϕ (deg)
173 ± 2
>90
The uncertainty on Pt due to the alternative g2
attachment is < 50 MeV.
The event passes all the kinematical cuts required.
Features of the decay topology…
red bands: values for
the “interesting” event
with uncertainties
41 ± 2 mrad
1335 ± 35 m
Kink angle
Accepted kinks
> 20 mrad
Decay length
rad
mm
..and kinematical cuts to be passed
12
+6
-3
GeV
570
Daughter
momentum
+320
-170
MeV
Blue: MC NC
Black: MC - 
Reject NC
events with
larger missing
Pt (neutrino)
Missing Pt Pt
at primary
vertex
Missing
at primary
vertex
cut
cut
cut
GeV/c
GeV/c
Pt at decay vertex
Reject hadron
interactions
470
+230
-120
MeV
cut
GeV/c
Background sources
• Prompt 
~ 10-7/CC
• Decay of charmed particles produced in e interactions
~ 10-6/CC
• Double charm production
~ 10-6/CC
Main Background
• Decay of charmed particles produced in  interactions
• Hadronic reinteractions
~ 10-5/CC
~ 10-5/CC
Hadronic reinteraction background
The number of estimated hadronic reinteraction BG is 0.011±0.006 by using
FLUKA simulation code.
cross check ① (4GeVp test-beam data)
cross check ② (scan-forth data)
signal region
8 times track length of tau search
1-prong
multiprong
•
•
•
18 times track length of tau search
no event in the signal region
90% CL upper limit of 1.54 x 10-3
kinks/NC event
The number of events outside the signal
region is confirmed by MC
(within the ~30% statistical accuracy
of the measurement)
Charm background
Charmed particles have similar
decay topologies to the 
primary lepton not
identified
,e-
,e
D+
+
e+
h+
• charm production in CC events represents a background source to all tau decay
channels
• this background can be suppressed by identifying the primary lepton
 ~ 95% muon ID
• for the 1-prong hadronic channel 0.007±0.004 (syst) background events are
expected for the analyzed statistics
Statistical significance
We observe 1 event in the 1-prong hadron  decay channel,
with a background expectation (estimating a ~ 50% error for each component) of:
0.011 events (reinteraction)
0.007 events (charm)
0.018 ± 0.007 (syst) events 1-prong hadron
all decay modes: 1-prong hadron, 3-prongs + 1-prong μ + 1-prong e :
0.045 ± 0.020 (syst) events total BG
By considering the 1-prong hadron channel only, the probability to observe 1 event
due to a background fluctuation is 1.8%, for a statistical significance of 2.36 s on the
measurement of a first  candidate event in OPERA.
If one considers all  decay modes which were included in the search, the probability
to observe 1 event for a background fluctuation is 4.5%.
This corresponds to a significance of 2.01 s.
Conclusions
• The OPERA experiment is aimed at the first direct detection of neutrino oscillations
in appearance mode through the study of the -  channel.
• In 2008 – 2010, data has been taken corresponding to 2.1 nominal years.
In 2010, beam intensity has reached 90% nominal.
• One muon-less event showing a   1-prong hadron decay topology has been
detected and studied in a subsample of 20% of the accumulated data.
• It passes all kinematical cuts required to reduce the physics background. It is the
first  candidate event in OPERA. The expected number of events in the analysed
subsample is 0.54 ± 0.13 (syst.)
The statistical significance of 2.01 s on the measurement of
a first  candidate event in OPERA when considering all tau
decays is relevant.
Outlook
• In 2011, 6 extra weeks of beam in dedicated mode have been attributed
corresponding to 1.2 nominal years.
If 2012 (or 2013) is like 2011:
Data on ~ 19.7×1019 POT or ~ 87% of Proposal beam intensity collected
• Analysis of 2008/2009 events will be closed in Feb/2011 and new results
on oscillations will be released in spring 2011.
Thank you for your attention !
Tsutomu FUKUDA ( Nagoya University )
NNN10 , 14 Dec 2010, Toyama International Conference Center in Toyama, JAPAN