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

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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

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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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