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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

4Target Mass ~1.2ktonMuon SpectrometerTarget Super-Module

The OPERA detector Underground@GranSasso, ~140

0m

5

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

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

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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