The OPERA experiment at LNGS - Infn

The OPERA experiment at LNGS - Infn

The OPERA experiment at LNGSChiara Sirignanoon behalf of the OPERA collaborationSalerno University & INFNQUARKS–201016 th International Seminar on High Energy PhysicsKolomna, Russia, June 6-12 2010

Outline Introduction The OPERA Detector at work Data Analysis OPERA latest news …2

Oscillation Project with Emulsion tRacking Apparatus732 Km• Long baseline neutrino physics experiment• CNGS quasi - pure ν µbeam, = 732 km, = 17 GeV• Appearance signal ν µ→ ν τ(by product ν µ→ ν e)• Hybrid setup (Nuclear Emulsions + electronics)• Atmospheric neutrino data allowed region oscillation search3

The OPERA CollaborationBelgiumIIHE-ULB BrusselsCroatiaIRB ZagrebFranceLAPP AnnecyIPNL LyonIPHC StrasbourgGermanyHamburgMünsterRostockIsraelTechnion Haifa180 physicists, 33 institutions in 12 countriesItalyBariBolognaLNF FrascatiL’Aquila,LNGSNaplesPadovaRomeSalernoJapanAichiTohoKobeNagoyaUtsunomiyaKoreaJinjuRussiaINR RAS MoscowNPI RAS MoscowITEP MoscowSINP MSU MoscowJINR DubnaSwitzerlandBernETH ZurichTunisiaCNSTN TunisTurkeyMETU Ankarahttp://operaweb.lngs.infn.it4

Physics motivation• Super-K (1998) : atmospheric neutrino anomaly interpretable as ν µ ->ν τ oscillation• CHOOZ (reactor) : ν µ ->ν e oscillation could not explain the anomaly• K2K and MINOS (accelerator): confirmation of the Super –K ν µ disappearance signal5

ChallengeDetection of ν τ CC interaction in a quasi- pure ν µ beam and direct observation ofthe τ lepton decay topologies.ν ττ decay kinkτ~ 1 mmτ − µ − ν τ ν µ (17.4%)τ − e - ν τ ν ε (17.8%)τ − h - ν τ n(π ο ) (49.5%)τ − π + π − π − ν τ n(π ο ) (14.5%)Nuclear emulsions + Lead (ECC) “active target”• 3D particle reconstruction• Sub-micron spatial resolutionHigh background rejection6

ν τ events topological signatureν µµ -No oscillationν µτ decaychannelSignal∆m 2 = 2.5E -3 eV 2Backgroundτ → µ 2.9 0.17ν µµ -Oscillationν τ~1 mmExpected data sample after 5 yearsTarget: ~ 1250 tons, 22.5E 19 p.o.t.τ → e 3.5 0.17τ → h 3.1 0.24τ → 3h 0.9 0.17Total 10.4 0.75• > 20000 neutrino interactions• ~ 100 ν τinteractions• ~ 10 ν τidentified• < 1 background event7

CERNCNGS neutrino beam< E > 17 GeVν µν τCC/year7 3 0 kmν µ(CC + NC)/year~4700LNGS~20(ν e+ ν e)/ ν µCC 0.87%ν µ / ν µCC 2.1%ν τpromptnegligibleThe beam is optimized to maximize the number of ν τ CC interactionsGPSL = 732 Km8

LNGS – Gran Sasso National LabThe largest underground laboratory in the world (180 000 m 3 )about 3100 m.w.e. shieldingCNGSCOPERABA1 cosmic muon /m 2 /h9

OPERA detectorVetoTargetRPCMuonTargetMuonRPCDrifttubesSpectrometerSpectrometer10 m53 BRICK WALLS• ~150000 bricks• ~1.25 kton2 0 mTARGET TRACKERS• Trigger task• Brick identification• 2 x 31 scintillating stripwalls read with PMT• 0.8 cm resolutionBrick ManipulatorSystemINNER TRACKERS• 990-ton dipole magnets(B = 1.55 T)• RPC resolution ~1.3 cm10 mHIGH PRECISION TRACKERS• spatial resolution < 0.5 mm(Ref. JINST 4 (2009) P04018)10

SM1SM21. Extract Brick and CS, scan CS.2. Confirm the event in the ECC brick.3. Develop the brick and send to scanning labs.Target area(ECC + CS + TT)Muon spectrometer(Magnet+RPC+PT)Brick Manipulator System11

ECC target brick75.4mm125mmCS sheet1 mmτ8.3kg10X 0ν beamOPERA emulsion film (Fuji Japan )100mmνPb2 emulsion layers (42 µm thick)poured on a 200 µm plastic base• 57 emulsion films + 2 CS interface sheet• 56 * 1 mm Pb (lead + 0.04 % Ca) platesLead plate (Goslar Germany)12

CS interface sheetT T10cmECC2.6 cmPosition accuracy of the electronic predictions12.5cmChangeable Sheet(CS)Interface emulsion films: high signal/noiseratio for event trigger and scanning timereductionAngular accuracy of the electronic predictions

Emulsion films scanningEU: ESS (European Scanning System)Japan: SUTS (Super Ultra Track Selector)• Scanning speed/system: 20cm 2 /h• Customized commercial opticsand mechanics• Asynchronous DAQ software• Scanning speed/system: 75cm 2 /h• High speed CCD camera (3 kHz),Piezo-controlled objective lens• FPGA Hard-coded algorithmsBoth systems demonstrate:• ~ 0.3 µm spatial resolution• ~ 2 mrad angular resolution• ~ 95% base track detection efficiency14

Vertex findingTrack follow-up film by film:• alignment using cosmic ray tracks• definition of the stopping pointCSdσ ~2 µm…ν µ1484950515253545556572Ref. JINST 4 (2009) P06020Volume scanning (~2 cm 3 ) around the stopping point

Decay searchIPleademulsionThe IP evaluation is a crucial pointin order to detect decay topologies∆ZDataMuon I.P.τµ (MC)IP of the muon tracks attached to the neutrino vertices foundIP(µm)16

OPERA status2000: approval of the CNGS project2003: start of detector construction2004: end of CNGS beam civil engineering2006: commissioning run (empty detector’s target)• 7.6E 17 pot2007: short pilot run (40% target)• 8.2E 17 pot, 38 ν events in the target2008: 1st physics run• 1.78E 19 pot, 1663 ν events in the target, 0.7 ν expectedτ2009: 2nd physics run• 3.52E 19 pot, 3693 ν events in the target, ~2 ν τ2010: 3rd physics run (May – November)• hope to reach more than 4 E 19 potexpected in total1 year CNGS nominal: 4.5E 19 pot17

Performance Plot

NC/CC events: Data vs MC}Visible NC/CC takes into account:NC/CC true ratio (0.3)Target interactions selectionefficiencyMuon ID efficienciesEvents migrations due tomisidentification CC - NC-- NC excess in data described by MC when including BCK due to external interactions:-- NC/CC ratio by cutting harder on the fiducial volume:Data 2008: NC/CC= 0.230 ± 0.014 (stat.)Data 2009: NC/CC= 0.228 ± 0.009 (stat.)MC:NC/CC= 0.236 ± 0.005 (stat.)19

Run 2008 event location (completed)ScannedCs scanning and brick selectionFoundScannedLocated neutrino interactionsLocated interactions in ECC ,then used for the decay search20

Run 2009 event location (in progress)CS scanning results21

Event location details (Run 2009)NC CC AllEvents predicted by the electronic detector 1097 2460 3557Events with at least 1 brick extracted 1050 2389 3439CS scanned 826 2143 2969Found in CS 447 1418 1865Neutrino interactions in the bricks 112 550 662Located in dead material 3 15 18Interactions in the upstream brick 4 50 54Decay search completed 53 226 27922

Charm events (I)Charm topology analogous to τ (similar lifetime): reference sample for the decayfinding efficiencySystematic decay search completed on 1088 neutrino located interactions20 events found showing a charm decay topologyEvent in Europe (D0 4 prong)x-viewEvent in Japan (kink)1ryvertex1ry muonkinkdaughter muon1.3 mm

Charm events (II)PrimaryvertexDecayvertex24

Particles momenta measuremnts by MCSTest beam data samples of pions and several MC samples were produced and used for thedevelopment of the method.Very detailed results are given and should be considered as reference ones for furtherMCS investigations.P rec (GeV)987654321π test beam1 2 3 4 5 6 7 8P beam (GeV)Measurements were performed also on several selectedsoft muon events registered in the OPERA detectorσ = (22±4)%

ν eCC interaction6 electron neutrino interactions were found in a subsampleof 800 CC located interactions.26

γ reconstruction (I)Example of reconstructed γ’s in real neutrino interactionsImportant for τ hadronic decay channels (signal vs background discrimination)

γ reconstruction (II)

Conclusions• The OPERA experiment at LNGS was designed and successfully constructed toensure the detection of neutrino oscillations in appearance mode through thestudy of the ν µ-> ν τchannel.• The analysis of neutrino data taken in the CERN CNGS beam in the 2008-2009runs is successfully on going.• Decay event topologies due to charmed particles have been observed inagreement with expectations, as well as events induced by prompt ν e present inthe CNGS beam.29

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