status and results from the opera experiment tsutomu fukuda ( nagoya university ) on behalf of the...
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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.
oscillation
-
decay “kink”
~1 mm
- ,h-,e-
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
OPERA start !!
Flight Length: 280um
DONuT event
1mmIron
BelgiumIIHE-ULB Brussels
CroatiaIRB Zagreb
FranceLAPP AnnecyIPNL LyonIPHC Strasbourg
GermanyHamburgMünsterRostock
ItalyBariBolognaLNF FrascatiL’AquilaLNGSNaplesPadovaRomeSalerno
JapanAichiTohoKobeNagoyaUtsunomiya
IsraelTechnion Haifa
KoreaJinju
RussiaINR RAS MoscowNPI RAS MoscowITEP MoscowSINP MSU MoscowJINR Dubna
SwitzerlandBernETH Zurich
TurkeyMETU Ankara
180 physicists, 33 institutions in 12 countries
TunisiaCNSTN Tunis
The OPERA CollaborationThe OPERA Collaboration
Our philosophy
following the Super- Kamiokande discovery ofoscillations with atmospheric neutrinos and theconfirmation 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
CERN
LNGS
732km
conventional beam
< 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)
~10 CC identified (BG<1)
* Interaction rate at LNGS
The OPERA target – ECC brick –
50 micron
Microscopic Image
Recorded as silver grains along the line where a charged particle passed through
Resolution of 0.3 micron
OPERA emulsion film
Lead plate : 1mm
57 OPERA films and 56 lead plates piled up.
125mm
100mm
75.4mm
8.3kg10X0
Neutrino Beam
Emulsion Cloud Chamber (ECC)
The OPERA detector
OPERA emulsion film
Emulsion + Target Tracker
Muon spectrometer
Emulsion + Target Tracker
Muon spectrometer
Typical CC-like and NC-like events
20 m
CC-like event
NC-like event
Emulsion Scanning for CS
• CS Scan & analysis NAGOYA : LNGS = 50:50
ECC brick
CS
Changeable Sheets (CS), two OPERA films fixed downstream of the ECC bricks, are used as interfaces between the electronic trackers and the ECC bricks.
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
To Japan
PadovaBern
Bologna
RomaLNF
NapoliSalerno
Bari
LNGS
After tracks are found on CS, ECC brick films are developed and sent to scanning labs along with the CS information.
Neutrino event location
5 mm
CSECC brick
CS ~100cm2 large area scanECC ~100100m2 point scan
How to locate1. 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.
STOP
1 cm
Scan about 10 plates around stop plate by follow up from down stream.
Located neutrino interaction in ECC brick
1 cm
Reject passing trough track and only few plates connect track.
Located neutrino interaction in ECC brick
1 cm
Search tracks making vertex by neutrino interaction .
Located neutrino interaction in ECC brick
2010
2009
2008 Days
POT
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
• 9639 events collected (within 1 in agreement with expectations from pot) → 2.1 nominal years in 3 years.
• POT of 2010: 90% of nominal year
Progress of CNGS runs
Location Status
• 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 ).
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
Decay topology search
IP distribution for events (MC)
IP distribution for:
events (MC)
NC+CC events (MC),
NC+CC events (Data)
A Charm event (dimuon event)
Kink angle = 209mrad
Flight Length= 1330micron
Decay Pt ~ 460MeV/c
1ry
Charm
+
In 901 sub-sample events,20 charm events were found. (expected : 16.0±2.9)
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
Event statistics for Decay search
The first candidate event was found
This result is opened at June/2010.
Event number 9234119599,taken on 22 August 2009, 19:27 (UTC)
2
1
3
2
75
1
6
8 (daughter)
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 length0.033 interaction length
primary vertex
kink point
Event topological features (Side view)
beam
top
view
side
vie
w
Event ECC pink color
The viewer of scintillation Target Tracker
primary vertex
kink point
Pointing resolution (1) for a given gamma: function of scattering and distance
γattachment 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 (8) is consistent with
120 ± 20 ± 35 MeV 640 +125-80
+100-90 MeV
Kinematical variables
The event passes all the kinematical cuts required.
The uncertainty on Pt due to the alternative attachment is < 50 MeV.
VARIABLE MeasuredSelection
criteria
Kink (mrad)
41 ± 2 >20
Decay length (m)
1335 ± 35Within 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
(Animation)
Missing Pt at primary vertex
cut
Pt at decay vertex
cut
GeV/c
Blue: MC NC Black: MC -
GeV/c
Missing Pt at primary vertex
cut
Features of the decay topology…red bands: values for the “interesting” event
with uncertainties
mm
Decay length
GeV/c
cut
Daughter momentum
1335 ± 35 m
12 +6-3 GeV
rad
Accepted kinks > 20 mrad
Kink angle41 ± 2 mrad
..and kinematical cuts to be passed
Reject NC events withlarger missing Pt (neutrino)
Reject hadron interactions 470 +230
-120 MeV
570 +320-170 MeV
Background sources
• Prompt ~ 10-7/CC• Decay of charmed particles produced in e interactions ~ 10-6/CC • Double charm production ~ 10-6/CC
• Decay of charmed particles produced in interactions ~ 10-5/CC
• Hadronic reinteractions ~ 10-5/CC
Main Background
Hadronic reinteraction background
cross check ① (4GeV test-beam data)
multi-prong1-prong
18 times track length of tau search
The number of estimated hadronic reinteraction BG is 0.011±0.006 by using FLUKA simulation code.
cross check ② (scan-forth data)
signal region
• 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)
8 times track length of tau search
Charmed particles have similar decay topologies to the
• 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
,e
,e-
+
e+
h+D+
primary lepton not identified
Charm background
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 on themeasurement 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 .
Statistical significance
• 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 on the measurement of a first candidate event in OPERA when considering all tau decays is relevant.
Conclusions
• 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.
Outlook
Thank you for your attention !
Tsutomu FUKUDA ( Nagoya University )
NNN10 , 14 Dec 2010, Toyama International Conference Center in Toyama, JAPAN