1 recent results on the observation of oscillation in the opera experiment nakatsukayuji nagoya...
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Recent results on the observation of oscillation in the OPERA experiment
NakatsukaYuji
Nagoya University
On behalf of
OPERA collaboration
ICISE Qui Nhon 2013 Aug 14
Rencontres du Vietnam
Windows on the Universe
BelgiumULB Brussels
CroatiaIRB Zagreb
FranceLAPP AnnecyIPHC Strasbourg
GermanyHamburg
ItalyBariBolognaLNF FrascatiL’AquilaLNGSNaplesPadovaRomeSalerno
JapanAichi edu.KobeNagoyaTohoUtsunomiyaIsrael
Technion Haifa
KoreaJinju
RussiaINR RAS MoscowLPI RAS MoscowITEP MoscowSINP MSU MoscowJINR Dubna
SwitzerlandBernETH Zurich
TurkeyMETU Ankara
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Aim and Principle
Direct detection of oscillation
- decay “kink”
~1 mm
oscillation
-, h-, e-
plus 3-prong decay modes
Observation of neutrino oscillations in appearance mode through the channel.
Aim :
Principle of OPERA Experiment :
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LNGS
< E > ( GeV ) 17 (e + e) / 0.89, 0.06 % / 2.1 % prompt Negligible
Covers the region indicated by Super-K, K2K & MINOSCNGS Beam
%7.1~27.1sin2sin~ 2322
232
E
LmP τμ
sin22θ23 = 1.0 , Δm232 = (2.43±0.13)×10-3 eV2 [ Phys.Rev.Lett.101:131802,2008.]
732km
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4Target Mass ~1.2ktonMuon SpectrometerTarget Super-Module
The OPERA detector Underground@GranSasso, ~140
0m
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Typical NC-like event
ECC selection
12.5cm
10cm
7.5cm
8.3kg
Neutrino Beam(vertical to films)
Emulsion Cloud Chamber (ECC)Stack of 57 emulsion films, 56 lead plates (10X0). ~150,000 ECC installed in the OPERA detector
20 m
Pb1mm
Changeable Sheet (CS)Interface emulsion films for ECC selection and track connection.
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ECC
Large area ~100 cm2
Point scan~100x100 m2
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
CS TThit
TThit
Ver
tex
plat
e
Follow back in the ECC tracks found in CS until they disappear: vertex plate
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Event location in ECC
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AgBr Crystal
200nm
10GeV π-
M.I.P.~30 developed silver grains / 100 m M.I.P. track
20μm
A compton track
Fog
125mm
100mm
OPERA Film210um plastic base
44um emulsion
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Event reconstruction
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
All track data ~ 1cm x 1cm
Required plate-plate connection Tracks converge to vertex point
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1mm Pb
Primaryvertex
Decay point
Long flight decay
IP
1mm Pb
Primaryvertex
Decay point
Short flight decay
IP(Mean 104.3 m)
Kink → e- 17.8 %
→ μ- 17.4 %
→ h- 49.5 %
Trident → h- h- h+ 15.2 %
decay mode
events (MC) NC+CC events (MC)NC+CC events (Data)
Impact Parameter distribution
10 m ↔ (c = 87m)
Without muon
CC detection
Short : Long ~ 2:8
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candidate events1st candidate -> 1h, May 2010
2nd candidate -> 3h, June 2012
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1111
μm
The 3rd candidate event : decay mode
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Event Display
2.8 GeV muon
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Event analysis
Kink Angle
(mrad)
245±5
Decay Length (m)
376±10
P (Gev/c) 2.8±0.2
Decay Pt (Mev/c)
690±50
Phi Angle (degrees)
154.5±1.5
p
ph total
pri. h
e-pair
°
beam transverse plane
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τ→μ MCτ→μ candidateexcluded region
Passed all cuts of decay criteria
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Muon sign
Spectrometer 4hitscurvature radius ~ 85cmmuon charge is negative5.6
Target tracker hits1.55T
identification of oscillated interaction (≠ )
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BG1 : Charm Decay
Charm BGThe same topology
decay
-eh
the decay muon charge is plus.
charm decay
charm
miss id
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BG2 : Muon Large Angle Scattering
Pb Film
kink point
Tranverse momentum PDF
500 10000 PT (MeV/c)
690MeV/c at base
104
107
muon quark
Scattering probability is proportional to the amount of material. Pb : 10-6
film (emulsion + plastic base) : 10-8 - 10-7
Upper limit : Proposal Value 10-5 (S.A. Akimenko et at al, NIM A423 1986 518)
Prob
Kink Angle (mrad) 245±5
Decay Pt (Mev/c) 690±50
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Summary of search status Three candidates have been found, 1st : h, 2nd : 3h, 3r
d : . The 3rd event is pure channel with low background and ta
gged as by its muon sign. Probability explained by only background ~ 7.29 x 10-4
The singnificance value : counting method : 3.2 of non-null observation, likelihood approach : 3.5
Signal Background Charm scattering had int
h 0.66 0.045 0.029 0.016
3h 0.51 0.090 0.087 0.003
0.56 0.026 0.0084 0.018
e 0.49 0.065 0.065
total 2.22 0.226 0.19 0.018 0.019
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Conclusions and Prospects OPERA ran on the CNGS beam successfully 2008-2012, 17.97x1
019 POT, ~80 % of proposal value of CNGS beam
Analysis stasus : completed 2008, 2009 events. 2010 - 2012 events are on going, main part (1st ECC) will finish in 2013.
Three candidates have been found, counting method 3.2 of non-null observation, likelihood approach : 3.5
Searches are on going for more interesting events, within reach 4 observation.
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backup
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Charm Decay Event Candidates
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Beam exposure and analysis status
Beam: 5 years (965days) 17.97×1019 p.o.t.
Overall 80% of the proposal value (22.5×1019 p.o.t.)
Completed: 2008, 20092010-12 on going with optimised strategy (ALL NC-like events and CC-like events with momentum < 15GeV/c)
‘08 ‘09 ‘10 ‘11 ‘12
date
Run 2008 → 2012
date
Located6211
CS found10776
ECC scanned9981
CS scanned14802
DS 5036
(13 Jul 28)
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The first “appearance” candidate (2010)
Candidate interaction
and decay from oscillation
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First tau neutrino candidate eventMuonless event 9234119599, taken on 22nd August 2009
(as seen by the electronic detectors)
G. De Lellis - Fermilab - 4 June 2010
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Event reconstruction in the brick
−→− −→→
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1
1mm lead
PL19 PL20 PL21PL17 PL18
kink point
6
2
84
3
5
1 7
Primary vertex
careful visual inspection of the films behind/in front of the secondary vertex:
no “black” or “evaporation” tracks. Support topological hypothesis of a particle decay
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Kinematical variablesVARIABLE AVERAGE
kink (mrad) 41 ± 2
decay length (m) 1335 ± 35
P daughter (GeV/c) 12 +6-3
Pt (MeV/c) 470 +240-120
missing Pt (MeV/c) 570 +320-170
ϕ (deg) 173 ± 2
• Kinematical variables are computed by averaging the two independent sets of measurements
•1 and 2 both attached to 2ry vertex
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Second neutrino tau candidate event taken on 23rd April 2011 as seen by the electronic detector event display
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animation Second Candidate Event
m
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Schematics of the event
Φ
Beam ViewΦ=167o
Secondary InteractionIn EmulsionWith four Nuclear fragments
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Zoom of the primary interaction and decay region
Decay point In Plastic Base No Nuclear fragmentFlight length 1.54mm
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Track# Momentum
( 1σ interval )[ GeV/c]
Particle
ID
Method / Comments
Primary 2.8
(2.1-3.5)
Hadron Momentum-Range Consistency Check
Stops after 2 brick walls. Incompatible with muon ( 2644 brick walls)
d1 6.6 ( 5.2 - 8.6 )
Hadron Momentum-Range Consistency Check
d2 1.3 ( 1.1 -1.5 )
Hadron Momentum-Range Consistency Check
d3 2.0
(1.4 - 2.9)
Hadron Interaction in the Brick
@ 1.3cm downstream
Momentum measurement and particle identification of event tracks
Independent momentum measurements carried out in two labs
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Kinematics of the second Candidate Event
Cut Value
φ (Tau - Hadron) [degree] >90 167.8±1.1
average kink angle [mrad] < 500 87.4±1.5
Total momentum at 2ry vtx [GeV/c] > 3.0 8.4±1.7
Min Invariant mass [GeV/c2] 0.5 << 2.0 0.96±0.13
Invariant mass [GeV/c2] 0.5 << 2.0 0.80±0.12
Transverse Momentum at 1ry vtx [GeV/c] < 1.0 0.31±0.11
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candidatecut
Satisfying the criteria for ντ 3hadron decay
Kinematics of the second candidate event
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Analysis of the interface films
Sign of electromagnetic shower
μ track
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Third tau neutrino eventτ μ
μm
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Event tracks’ features TRACK NUMBER PID MEASUREMENT 1 MEASUREMENT 2
ΘX ΘY P (GeV/c) ΘX ΘY P (GeV/c)
1DAUGHTER
MUON -0.217 -0.0693.1
[2.6,4.0]MCS-0.223 -0.069
2.8±0.2Range (TT+RPC)
2HADRON
Range0.203 -0.125
0.85 [0.70,1.10]
0.205 -0.1150.96
[0.76,1.22]
3 PHOTON 0.024 -0.1552.64
[1.9,4.3] 0.029 -0.160
3.24[2.52,4.55]
4 PARENT
TAU -0.040 0.098 -0.035 0.096
γ attachment
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Muon charge and momentum reconstructionBending by the magnetic field
Muon momentum by range in the electronic detector: 2.8±0.2 GeV/cMCS in the brick consistent 3.1 [2.6,4.0] GeV/c
Cells ϑ
(mra
d)
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Track follow down to assess the nature of track 2
Momentum/range inconsistent with μ hypothesis0.9 GeV/4 cm Lead
Track 2 interacting in thedownstream brick withoutvisible charged particles
Hadrons and muon stopping in the brick
track value
cut valueL = track lengthRlead = µ rangeρaverage = average density ρlead = lead densityp = momentum in emulsion
D variable
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THE MAGNETIC SPECTROMETERS
• 1.55 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
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µ→e analysis
4.1 GeV electron
≈ 30 events found in the analyzed sample
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Electron neutrino search in 2008 and 2009 runs: one of the νe events with a π0 as seen in the brick
Interface films
19 candidates found in a sample of 505 neutrino interactions without muon
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Background from µNC (0→)
A close-up of an electron pair
1micron
Gamma-ray
BG: 0.17 events (less than 1%)
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Observation compatible withbackground-only hypothesis: 19.8±2.8 (syst) events
3 flavour analysis
Energy cut to increase the S/N
4 observed events 4.6 expected
⇒ sin2(2θ13)<0.44 at 90% C.L.
Energy distribution of the 19 νe candidates
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Search for non-standard oscillations at large Δm2 values: exclusion plot in the sin2(2θnew) - Δm2
new plane
arXiv:1303.3953
Caveat: experiments with different L/E values
Submitted to JHEP
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Background estimation (hadron)
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10GeV/c10GeV/c4GeV/c4GeV/c2GeV/c2GeV/c
Multiplicity
Kink angle (1-prong)
nuclear fragments in emulsion
4GeV/c4GeV/c2GeV/c2GeV/c
Multiplicity
Emission angle(cos )
10GeV/c10GeV/c
MC: < 0.7
ForwardBackward ForwardBackward ForwardBackward
We confirmed MC simulation estimation of hadron backgrounds by using the data analysis of ECC bricks exposed to 2GeV/c , 4 GeV/c and 10GeV/c pion beams and reduced systematic uncertainty.
Error bars : Experimental dataHistogram : Simulated data
Secondary track emission: 30%
nuclear fragments:10%
Nuclear fragment associated probability
2 10GeV/c4
Hadronic background was reduced by “40%” by requiring no association of large angle nuclear fragments.
100%
0%
0 5 0 5 0 8
0 0.6 0 0.6 0 0.6 180° 0° 180° 0°180° 0°
0 15 0 15 0 15
8
・ data- MC
New technique for background reduction
They argee well Well reproduced by MC
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Track recognition method •Take 16 tomographic images by microscope optics.• Shift images to aim at specific angle tracks.• Sum up 16 images to examine coincidence.• Find signal of tracks.•Repeat for all angles in space, >2000 timesInvented by K.Niwa in 1974