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Status of the OPERA experiment

Status of the OPERA experiment. Akitaka Ariga LHEP, University of Bern on behalf of the OPERA collaboration. n m CC event with charm production Candidate (Data). OPERA experiment. Aiming to prove the Flavor-Mixing neutrino oscillation hypothesis by appearance method .

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Status of the OPERA experiment

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  1. Status of the OPERA experiment Akitaka Ariga LHEP, University of Bern on behalf of the OPERA collaboration nmCC event with charm production Candidate (Data)

  2. OPERAexperiment • Aiming to prove the Flavor-Mixing neutrino oscillation hypothesis by appearance method. • Appearance of new flavor: nm  nt • Search in the region predicted by disappearance experiments (SK, K2K, MINOS). • Direct observation of nt events in Nuclear Emulsion detectors. • Only detector which can detect nt(DONUT exp.). • Sub-micron position resolution • mrad angular resolution. • 1.25 kt of target mass t (F.L. ~500mm) nt 1ry vertex non-mu nt CC interaction

  3. LNGS CERN CERN L = 732 km 730 km LNGS CNGS beam  Expected produced interactions (22.5x1019): ~25400  CC + NC ~170 e +e CC ~125  CC (m2 = 2.5 x 10-3 eV2) ~10 tau decays are expected to be observed Less than 1 background after 5 years running Tflight = 2.44 ms

  4. Emulsion film by FUJI Film Emulsion Layer (44micron) A minimal detector AgBr Cristal, Size = 0.2micron Detection efficiency = 0.16/crystal 1013channels in a film Plastic Base (205micron) Emulsion Layer Cross-sectional view (SEM) Intrinsic resolution50nm Deviation from linear-fit line. (2D) sensitivity36grains/100micron π-10GeV/c Electron ～100keV 20μm 4

  5. OPERA target & main detector ECC brick neutrino Hybrid target structure. 10.2 cm 7.5 cm 10 X0 12.5 cm 0.3mm 1mm Lead plate (CS) The OPERA target consists of about 150,000 bricks. Total target mass: 1.25 kton OPERA Film 2 emulsion layers (44 m thick) poured on a 205 m plastic base OPERA Film × 57 plates Lead x 56 plates

  6. OPERA detector SM1 SM2 Brick Wall and Brick Manipulation system. Brick Manipulator System Target area (ECC + CS + TT) Muon spectrometer (Magnet+RPC+PT)

  7. OPERA detector SM1 SM2 Extract Brick and CS, scan CS. Confirm the event in the ECC brick. Develop brick and send to scanning labs. Brick Manipulator System Target area (ECC + CS + TT) Muon spectrometer (Magnet+RPC+PT)

  8. ECC validation by CS • Select proper ECC brick which contains neutrino interactions. • Save analysis time • Minimize the loss of target mass Develop this brick CS

  9. CS Scanning Stations LNGS (Italy) Nagoya (Japan) European Scanning System Super-UltraTrackSelector 11

  10. Parallel analysis of ECC bricks • Validated bricks are sent to the scanning labs. • 10 scanning labs share the scanning. (Increasing!) To Mosccow Padova To Japan GS Scanning station in LHEP Bern

  11. Flow of Location – ECC Scanback – TT ECC CS Large area scan~100cm2 Point Scan ~100x100mm2 neutrino emulsion emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion

  12. Flow of Location – Volume Scan – TT ECC CS Volume scan  topology analysis 5 plates upstream 10 plates downstream neutrino emulsion emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion

  13. Located neutrino interaction Emulsion gives 3D vector data, giving a micrometric precision of the vertexing accuracy. (The frames correspond to scanning area. Yellow short lines  measured tracks. The other colored lines  interpolation or extrapolation. The colors indicate the Z-depth in the module.) 1 cm

  14. Status and prospect of Data taking. 1.93·1019 pot 2008 2009 1.78·1019 pot Sep 6th pot 03 Nov Extrapolation to end of 2009 run = 3.5 x 1019 POT May 9th 18 June Unix Time Time

  15. Status of event location in ECC for 2008 run Scanning for 2008 run will be completed by September 2009. Y (mm) X (mm)

  16. Impact parameters lead emulsion MC IP DZ IP = Distance from the reconstructed vertex DZ profile plot Data Data <IP>

  17. Improvement of analysis speedin ECC validation by CS Red : ’08Run Black : ’09Run (Zoom up) Av ’08Run : 55.3 daysAv ’09Run : 5.5 days Red : ’08Run Black : ’09Run Long tail in 2008 run day day Most of events in 2009 are processed with in a few days.

  18. Gamma detection and π0reconstruction 70% of 1-prong hadronic tau decays include one or more p0. Important to detect gamma from tau decay to improve S/N. Gamma detection detection of shower detection e-pair at start point π0 reconstruction is in progress. hadron t g g 2 e-showers give a reconstructed mass ~ 160 MeV/c2 e+ e- g  e-pair g E ~8.1 GeV E ~0.5 GeV

  19. n 2.2 cm Example of Gamma to vertex attachment • nm CC interaction with hadronic re-interaction Secondary vertex 7 mm Primary vertex muon

  20. 7 mm n 2.2 cm Example of Gamma to vertex attachment 6 g reconstructed around the vertex muon

  21. 7 mm n 2.2 cm Example of Gamma to vertex attachment 6 g reconstructed around the vertex 4 g attached to primary vtx and well separated from secondary vtx: - IP at 1ry vtx: 27 - 31 - 119 - 3.5 mm - IP at 2ry vtx: 260 -158 - 500 - 700 mm muon

  22. 7 mm n 2.2 cm Example of Gamma to vertex attachment 6 g reconstructed around the vertex 2 g attached to secondary vtx and well separated from primary vtx: - IP at 2ry vtx: 8 - 10 mm - IP at 1ry vtx: 1216 - 806 mm Not only detection, but also pointing of vertex muon

  23. Gamma study and MC/data comparison Gamma multiplicity attached to 1ry vertex preliminary dZ from 1ry vertex to start point IP of gamma to 1ry vertex preliminary preliminary

  24. Analysis for located events • 2008 run • Nu-tau detection • 0.7 event observation is expected • Background 0.05 event. • Check nu-tau detection efficiency by detecting charmed particles (similar life time and mass with tau) • Charm particles are produced in nu-mu CC interactions (~4.5%) ntCC-int m, e, hadron t nmCC-int +charm production Charm m

  25. Example of Detected Topologies 1. A Muon is isolated from the vertex. muon emulsion 1mm muon (animation) Yellow short line is data. Lines with other color are extension.

  26. Lead plate (1 mm) Hypothesis (1) D0 candidate D0 1ry vertex muon Hypothesis (2) t candidate? minimum kink angle: 312 mrad muon momentum: 17 GeV/c Decay Pt > 5.3 GeV/c Excluded by Pt: Pt > maximum decay Pt of t (about 0.9 GeV/c) 1ry vertex t muon

  27. Example of Detected Topologies 2. Tilted view • A muon kink detected in rather short flight length. Em Em m- 1ry vtx 1ry vertex kink vtx Beam view Kink angle 15 mrad F.L. 1.8 mm Kink angle 15mrad, Pt = 90MeV/c m 6GeV/c 1.8mm 1ry vtx kink vtx • Topology looks similar to tau decay. • Kink angle = 7 sigma away from the resolution. • Rejected by Kinematical analysis (Pt cut). • Pt cut for tau decay : Pt>250MeV/c • Possibly, muon single large-angle scattering or hadronic particle decay (pi, K) into muon. m-

  28. Current status for 2008 run. • Tau candidates • Analysis ongoing. • No candidate yet. (0.7 expected, 0.05 BG) • Charm candidates. • Analysis ongoing for located ~700 nu-mu CC events. • Up to now, we have collected 15 candidates. • Agreement with our expectation

  29. The L’Aquila earthquake A strong earthquake (MI=6.2) hit L’Aquila on April 6th 2009. The epicenter was 15 km away from the Gran Sasso laboratory. 306 killed, 1600 injured, many houses collapsed, 15000 buildings were damaged. OPERA found basically intact, geometric measurements showed no significant alignment changes. Gran Sasso activities, stopped for ~1.5 months. Big OPERA effort to let CNGS start with only 2 weeks delay ! 28

  30. TT and the earthquake amplitude of the oscillation ~10 mm No other consequences of the earthquake were observed, thanks to the anti-seismic studies made for OPERA 30

  31. Summary • The OPERA experiment is taking data in the CNGS beam. • 1.78x1019 pot were collected during the first physics run in 2008. • 800 out of 1600 located in ECC • Scanning to be finished this month • The analysis of 2008 data is in progress. • Expected detector performances. • No nu tau signal yet. • Several charmed candidates are detected as expected. • The evaluation of total efficiencies and background is ongoing. • In 2009 run, 1.93x1019pot were already collected. • 4.5x1019 pot are requested. • 3.5x1019 pot are expected at the end of the run. • Detection of ~2 nu-tau events is expected…SOON.

  32. Charm candidate: 51284 (di-muon event) x-view 1ry muon flight length: 1330 micron kink angle: 209 mrad IP of daughter: 262 micron daughter muon: 2.2 GeV/c decay Pt: 0.46 GeV/c 1ry vertex 4 mm kink daughter muon 1.3 mm (animation)

  33. BACKUP

  34. 160micron 600micron Changeable Sheet (CS) Roles of CS • Pick up tracks from neutrino interaction • Helps tagging ECC  Saving Scanning load and Target Mass OPERA film x 2 OPERA film OPERA film 10cm Neutrino beam Base 205micron Base 205micron 12.5cm X Z Emulsion layers 44micron

  35. Scanning and reconstruction Single base-track Base Computing ~ 5 min. Emulsion Emulsion Reconstructed tracks between base. Scanning ~ 10 min / cm2 Raw-tracks in each layer. Most time consuming. Computing ~ 5 min Analysis Reconstructed tracks between films

  36. OPERA signal and background Full mixing, 5 years run, 4.5x1019 pot /year • Main background sources: • Production and decay of charmed particles • Hadron re-interactions • Large angle muon scattering

  37. Tau background by D0    channel • Neutral charmed particle decay vertex mistaken as primary vertex in events where only a muon and D0 are produced at primary vertex Cut on the invariant mass to be used to reduce this background source

  38. P MCS (GeV) p test beam P beam (GeV) Momentum measurement in ECCby Multiple Coulomb Scattering. Evaluate scattering of particles Data from Test exposure to pion beam Pion 2 GeV Pion 6 GeV

  39. Pt cut MC MC Daughter particle of hadronic re-interactions Daughter particle of τ Pt(GeV/c) Pt(GeV/c)

  40. 72853 m- muon single stop at pl 22. a vertex found 342 m upstream from pl 22. minimum distance w.r.t muon trk 145 37.0 m (confirmed in CS) trk 206 13.5 m

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