1. The OPERA neutrino oscillation experiment Paolo Strolin University and INFN, Napoli

2. What is “Neutrino oscillation” Pontecorvo, 1957 Maki, Nakagawa and Sakata, 1962 Pontecorvo and Gribov, 1969 A phenomenon induced by m > 0 m = 0 in “Standard Model” of elementary particles The observed e    and   are “flavour eigenstates”, related by a mixing matrix to the invisible “mass eigenstates” 1  2 and 3 At a large distance from the source, it implies an apparent “metamorphosis” of a flavour into a different one (e.g.    ) A very sensitive method to measure  m i 2

3.  disappearance (interpreted as  →  ) observed by Super-Kamiokande best fit:  m 2 = 2.4  10 -3 eV 2, sin 2 2  = 1 Independently observed by MACRO Confirmed by K2K and MINOS still missing:  direct observation (“appearance”) of oscillated  Atmospheric neutrino oscillations

4. ● Main aim: unambiguous evidence for    oscillation in the parameter region indicated by the atmospheric neutrino disappearance ● Search for  appearance in a pure  beam at a long baseline (CNGS beam, = 17 GeV, L = 732 km) ● Detection of  CC interactions with the unstable  lepton identified by the direct observation of its decay ● Hybrid set-up (nuclear emulsions + electronic detectors) needed to observe decays OPERA

5. The CNGS beam Beam main features L730 km 17 GeV L/ 43 km/GeV ( e + e )/  0.87%  /  2.1%  prompt negligible “off peak” Limiting for  e  → e searches Event rate for OPERA (~1.3kton) with 4.5·10 19 pot (200 days/year) ~ 6200  (CC + NC) / year ~ 25  CC/year for ∆m 2 = 2.4·10 -3 eV 2 CERN LNGS 730 km

6. OPERA Laboratori Nazionali del Gran Sasso - INFN 1400 m rock coverage cosmic µ reduction factor = 10 –6 → 1/m 2 h underground area: 18 000 m 2 756 scientists from 25 countries Neutrino physics (mass, oscillations, stellar physics) Dark matter Nuclear reactions of astrophysics interest Gravitational waves Geophysics Biology Roma

7. To identify  leptons, “see” their decay “kink”     decay kink ~ 0.6 mm Lead – nuclear emulsion sandwich “Emulsion Cloud Chamber” ( ECC) AND  see the decay   m resolutionrare process  massive target The challenge

8. The Emulsion Cloud Chamber (ECC) Emulsions for tracking, passive material as target –Established technique charmed “X-particle” first observed in cosmic rays (1971) DONUT/FNAL beam-dump experiment:  observed (2000) <  m space res. mass Pb  1 mm Emulsion layers track segments  m 2 = O (10 -3 eV 2 )   M target ~ O (kton) –modular structure (“bricks”): basic performance is preserved –large detector  sensitivity, complexity –required: “industrial” emulsions, fast automatic scanning The dense lead-emulsion sandwich allows –electron identification by showering –momentum measurement by Multiple Coulomb Scattering

9. 36 INSTITUTIONS, ~160 PHYSICISTS IPNL, IPHC, LAPP INR ITEP, MSU, LPI JINR, Obninsk Zagreb L’Aquila, Bari, Bologna, Napoli, Padova, Roma, Salerno, LNF, LNGS Bern Neuchatel ETH Zurich Brussels Hamburg, Münster, Rostock Sofia Aichi, Toho Kobe, Nagoya Utsunomiya Technion Haifa METU Ankara Tunis Gyeongsang University The OPERA Collaboration

10. 20m 10m 10m SM1 SM2 Target lead/emulsion ECC bricks emulsion tracking resolution:  x< 1μm  1mrad 154,750 “bricks” ~ 1.3 kton planes of scintillator strips Pb Emulsion layers  1 mm Muon Spectrometers Magnetized iron slabs. Vertical drift tubes for momentum measurement from deflection through 24 magnet instrumented with 22 RPC planes ∆p/p~20% up to 50 GeV The OPERA ”hybrid” detector 1 brick: 8.3 kg

11. A view of the OPERA detector SM1 Veto BMS Target SM2 Spectrometer: XPC, HPT, RPC, magnet

12. Lead – Emulsion target Brick (basic module) 56 Pb 1 mm thick plates 57 emulsions films Emulsion film (Fuji-Nagoya) emulsion layers (43  m thick) on both sides of a 200  m thick plastic base 12.5cm 10.2cm 8.3 kg 10 X 0 wall 52 x 64 bricks Bricks assembled in walls Total target mass :  1300t Changeable Sheet (CS) Doublet of emulsion films with very low background, attached to the brick, as interface to electronic detectors

13. Brick Assembly Machine (BAM) at LNGS Robots produce bricks at a rate of  700 bricks / day

14. Brick Manipulator System (BMS) Ventouse Vehicle Brick Carousel mechanism Robot for brick insertion (target filling) and removal (during run)

15. An event in OPERA Electronic detectors  select ν  interaction brick and CS  μ ID, charge and p Target Trackers Pb/Em. target μ spectrometer 8 cm Pb/Em. brick Extract selected brick with CS Emulsion analysis  vertex search  decay search  e/μ ID, kinematics Pb 1 mm Basic “cell” Emulsion ντντ

16. Automated Emulsion Scanning Started with the pioneering work in Nagoya ~ 30 bricks will be daily extracted from the target and analyzed quasi-online using high-speed automatic systems in Several labs in Europe and Japan Customized commercial optics and mechanics + asynchronous DAQ software Hardware-coded algorithms Continuous movement of emulsion High speed CCD Camera (3 kHz ) Piezo-controlled objective lens Constant speed stage Synchronization of objective lens and stage S-UTS (Japan)European Scanning System

17. Track segments found in 8 consecutive films Passing-through tracks rejection Vertex reconstruction 3D reconstruction of particle tracks 16 tomographic images 200  m Microscope field of view 43  m emulsion sheet Automatic microscopy: from a microscope field of view to a reconstructed vertex

18. Search for    oscillation: expected number of events  decay channels Signal Background  m 2 = 2.4 x 10 -3 eV 2  m 2 = 3.0 x 10 -3 eV 2   µ   µ 2.94.20.17   e   e 3.55.00.17   h   h 3.14.40.24   3h 0.91.30.17 ALL 10.415.900.76 full mixing, 5 years run @ 4.5x10 19 pot / year Main background sources: - charm production and decays - hadron re-interactions in lead - large-angle muon scattering in lead

19. OPERA sensitivity Discovery probability (%) Discovery probability vs  m 2 4-  evidence 3-  evidence Exclusion plot at 90% C.L

20. A short run: 0.0824*10 19 protons on target with  1.8*10 13 p/extraction  3.6 effective days at nominal proton intensity 4.5*10 13 On October 3 rd observed the first event in the target 365 events in the whole detector s elected and analyzed 331 events passed through the analysis cuts (303 expected) 38 events (31.5 expected) in the neutrino target Their study is ongoing First OPERA Physics Run Sept. 24 - Oct. 22, 2007

21. Time Selection of Beam Events GPS T CERN SPS extraction T OPERA Event Time T flight = 2.44 ms T OPERA - T CERN resolution ~ 100 ns Cosmic ray background Beam

22. 22MIAMI 2007 In target events in the electronic detectors (top: display in the whole detector; bottom: display in the target)

23. EVENT 179673325 in el. det. and ECC quasi-elastic-like topology IP  = 0.33  m SlopeX=-0.040 SlopeY=0.014 IP h = 4.50  m SlopeX=-0.380 SlopeY=-0.602  (by ionization)  ECC

24. Event analysis muon P=21.8 GeV (spectrometer) hadron p  = 308±50 MeV Pion hypothesis p=331±54 MeV  = 0.93 Proton hypothesis p=583±95 MeV  = 0.53 Emulsions permit energy loss measurement of charged particles by counting the number of grains produced by ionizations Energy loss measurement suggest that pion is most probable hypothesis for the hadron track PRELIMINARY!!!

25.  6 prongs a b e d c f TrackSlopeCS track Stop film IP (  m) A -0.028, 0.095 6575.2 B -0.114,0.143 (7?)570.3 C 0.091, 0.009 576.2 D-0.166,-0.3423221.4 E 0.127, 0.075 3516.4 F -0.370, 0.430 2815.3 Shower 0.019, -0.006 2,838- EVENT 178969961 in el. det. and ECC ECC

26. TrackSlopeXSlopeYLengthIP 10.026-0.09730-335.7 2(  ) -0.0240.01930-561.2 30.0450.19730-521.7 40.0240.20330-522.6 50.1000.15130-517.9 6-0.0470.19931-452.9 70.0730.15231-458.8 80.0850.25431-4310.3 90.0740.20130-334.6 Track 1: kink between plates 33 and 34 Flight length of parent track  5 mm Kink attributed to hadronic interaction EVENT 180400976 in el. det. and ECC ECC

27. Kink analysis  =0.031 rad Daughter track momentum estimated by MCS P=3.1 ± 0.7GeV P T =96±20MeV Elastic or inelastic scattering? PRELIMINARY!!! Kink due to hadronic interaction (KEK measurement)

28. Conclusions  Main aim: prove the  →    interpretation of the atmospheric  disappearance, by observing  →   appearance  First physics run 24 Sept. - 22 Oct. 2007  The whole chain from data acquisition to event analysis has been tested  The studies on the acquired events are ongoing  Wait for the 2008 physics run and the 1 st  appearance !

29. “Neutrino oscillations” Pontecorvo, 1957 Maki, Nakagawa and Sakata, 1962 Pontecorvo and Gribov, 1969 A phenomenon induced by m > 0 Implies the apparent “metamorphosis” of a into a different one (e.g.    ) A very sensitive method to measure  m 2 The PMNS matrix Atmospheric Terms probed by next experiments Solar, reactor analysis CP violation phase

30. September 24 th to October 22 nd 2007: first OPERA Physics Run On October 3 rd OPERA observed the first event in the target SPS super-cycle with 3 CNGS cycles every 39.6s During the run we have accumulated 0.0824*10 19 pot onto the target with a mean value of 1.8*10 13 proton per extraction: this represents  effective days for the run! CNGS run parameters

31. Data are extracted from the DAQ data base every 12 hours and processed with the OPERA reconstruction package. In time events are selected and stored on a dedicated file. Then in time events are scanned visually and stored by categories: magnet interaction rock muon in target CC and NC like (according to the muon id) The interactions in the material surrounding OPERA target are analysed separately and are used for the monitoring on the CNGS beam and of the OPERA detector Data analysis and event selection

32. Beam events CC event originated upstream of the detector (BOREXINO, rocks) CC event originated in the first magnet

33. Data analysis and event selection Main physical distribution for the selected events The vertical angle of the track. Fit: 3.4±0.2 degree The Vertex location is defined as the first hit of the 3D reconstructed track The Energy of the muon as measured with the RPC of the spectrometer

34. In target events analysis We have observed 38 events (31.5 expected) in the emulsion target area 22 charged current 9 neutral current compatible with the relative cross sections The events are analysed through the brick finding package: a neural network for the wall finding the hadronic shower parametrization the exact configuration and alignment of the target at the time of the event taking into account the wall elongation as a function of the filling the probability estimate for the vertex location in each brick

35. 35 Target Tracker 7 m 6.9m 1.7m Plastic scintillator strips (AMCRYS-H, 6.7m x 2.6cm x 1cm) readout by Kuraray WLS fibres + Hamamatsu PMT’s (64 channels) Target Tracker tasks ● Trigger:  > 99% ● Initiate muon tagging 31 walls Alberto Marotta - INFN NapoliMIAMI 2007

36. Beam events are selected correlating events GPS time information with CERN beam spill time 319 events on time selected Events Time Structure OPERA Cosmic ray background Extraction length = 10.5  sec OPERA

37. 37 Muon spectrometer  identification:  > 95%  p/p < 20%, p < 50 GeV/c misidentified  charge prob. < 0.3% B= 1.55 T base slabs coil 8.2 m M ~ 950t Drift tubes 12 Fe slabs (5cm thick) RPC’s ● muon identification (TT) ● range measurement 11 + 11 planes of RPC’s 21 bakelite RPC’s (2.9x1.1m 2 ) / plane Inner Tracker Precision Tracker 6 planes of drift tubes space resolution:  300µm ● momentum measurement Alberto Marotta - INFN NapoliMIAMI 2007

38. Alberto Marotta - INFN Napoli38 Brick handling and processing IN PROGRESS….EuropeJapan Allocated events19 (15 CC + 4 NC) 19 (14 CC + 5 NC) Event confirmed in the CSd1413 Located events in the bricks (scanning in progress….) 74 brick confirmation by finding the tracks associated to the interaction inside the Changeable Sheet doublet (CSd) if the event is not confirmed in the most probable brick, the processing of the CSd for the next one is organized; if the brick is confirmed by the CSd results the brick is sent in the brick professing chain. Brick processing chain confirmed bricks are exposed to cosmics used for plate to plate alignemet developed shipped to laboratories for scanning and analysis

39. Angular distribution of all events Angle w.r.t. horizontal Azimuth angle Cosmic µ: mountain rock structure asymmetry coherently with previous MACRO observation Zoom on Beam events Coming 3.5° from below