1. Status and the preliminary results of the OPERA experiment V.Tioukov (INFN, Napoli) on behalf of the OPERA collaboration V. Tioukov QFTHEP11, Sochi

2. OPERA main goal: detection of neutrino oscillations in appearance mode After the Super- Kamiokande discovery of oscillations with atmospheric neutrinos and the confirmation obtained with solar neutrinos and accelerator beams the direct observation of the oscillation appearance is still missing tile Requirements to the beam: 1) long baseline, 2) high neutrino energy, 3) high beam intensity LNGS – largest underground laboratory (18000 m 2 ) 1400 m rock shielding, Cosmic μ reduction 10 -6 wrt surface

3. V. Tioukov QFTHEP11, Sochi OPERA CNGS neutrino beam

4. Detection principle ● The detection of the  lepton requires an identification of a “kink” or “trident” topology ● The detector must fulfil the following requests: 1. Large mass due to small CC cross section (lead target) 2. Micrometric and milliradian resolution to observe the kink (photographic emulsions) 3. Select neutrino interactions (electronic detectors) 4. Identify muons and their charge to reduce charm background (precision tracker and spectrometer)   e -,  , h    3h   e (17.8%)  (17.4%)  h (49.5%)  3h (15.2%) V. Tioukov QFTHEP11, Sochi

6. CNGS appearance potential CNGS  appearance potential ● The beam is optimized for ν τ appearance in the atmospheric oscillation region. The present best fit is now: Δm 23 2 = (2.43 ± 0.13)×10 -3 eV 2 sin 2 2θ 23 = 1.0 ● Although the maximum of oscillation probability at 730 km is at about 1.5 GeV, the ν τ CC cross section and the production threshold of 3.5 GeV should be taken into account 17 Gev  e  e  μ 0.87%  μ  μ 4 %   prompt negligible Total p.o.t22.5x 10 19 μ CC + NC ~23600 e  e CC ~160  ~115 V. Tioukov QFTHEP11, Sochi

7. Goal of the experiment: 22.5x10 19 pot 2010: close to nominal year (4.5x10 19 pot) 2011: hit record performance ? (expect ~5x10 19 pot for 223 days) Dedicated mode (no other fixed target) from 18 March to 7 June. Until now (2008-2011): 13.4x10 19 pot Aim at high-intensity runs in 2012 as well, with a dedicated running period YearBeam daysProton on target(pot) SPS effEvents in the bricks 20081231.78x10 19 81%1698 20091553.52x10 19 70%3693 20101874.04x10 19 81%4248 2011Ongoing4.11x10 19 79%4075 CNGS to OPERA In 2008-2011

8. OPERA layout  Hybrid detector (electronic + emulsions) with a modular structure: 2 supermodules = 2*(31 walls + 1 spectrometer) ↳ 31 walls = 31*(56*64 bricks + 2 scintillator tracker planes) The total target mass = 1.35 Kton V. Tioukov QFTHEP11, Sochi

9. The OPERA electronic detectors Target Tracker Made of plastic scintillation strips with wavelength shifting fibers p.e/mip > 5 Detection efficiency: 99 % Brick finding efficiency: ~80 % Muon spectrometer RPC and drift tubes in 1.5T magnet charge miss id (<25 GeV/c): <1% ΔP/P (<50GeV/c) ~ 20% μ id (with TT) ~ 95% V. Tioukov QFTHEP11, Sochi

10.  identification ● The target is divided in about 152000 ECC's (Emulsion Cloud Chamber), so called “bricks”. Each brick weights 8.3 kg ● One brick is made by a sandwich of: 56 (1mm) Pb sheets 57 (300  m) FUJI emulsion layers 2 (300  m) changeable sheets Long decay Short decay 10.3 cm 12.8 cm 7.5 cm = 10 X 0 V. Tioukov QFTHEP11, Sochi

11. Emulsion/lead target 8.3kg 10 X0 10.2 x 12.7 x 7.5 cm Brick filling is finished in July 2008 146621 bricks with ~ 8 millions of nuclear emulsions plates Bricks assembling was technologically challenging The small mechanical industry installed underground and worked in the red-light dark room V. Tioukov QFTHEP11, Sochi

12. Changeable sheet (interface films) 600 microns 160micron muon track Side view of a CS doublet Hybrid target structure. Neutrino From meters to microns: OPERA: 10x10 m 2 TT – indicate brick ~ 1 cm accuracy CS – ~100 microns Inside brick near the vertex ~ 1 micron CS background requirements: 1 track/ 10x10 cm 2 Doublet film for coincidence Muon Other products No cosmic rays in CS!

13. The automatic emulsion scanning Developed grains frame 2-3  m 15-16 frames/45 microns The European Scanning System. About 30 of them installed in the European labs V. Tioukov QFTHEP11, Sochi

14. UTS, S-UTS automatic microscopes generation (Japan) 75 cm 2 /hour scanning performance High speed CCD Camera (3 KHz) Objective lens moved by piezo- element Dedicated hardware for the reconstruction algorithms S-UTS: V. Tioukov QFTHEP11, Sochi

15. OPERA emulsion target Pb Emulsion layers  1 mm Based on the concept of the Emulsion Cloud Chamber (ECC) 56 Pb sheets 1mm + 57 emulsion plates Solves the problem of compatibility of large mass for neutrino interactions + high space resolution in a completely modular scheme ECC are almost stand-alone detectors:  Neutrino interaction vertex and kink topology reconstruction  Measurement of the momenta of hadrons by multiple scattering  dE/dx pion/muon separation at low energy  Electron identification and measurement of the energy of the electrons and photons ECC Technique validated by the direct observation of  : DONUT 2000 V. Tioukov QFTHEP11, Sochi

16. Some numbers concerning the OPERA scanning Emulsion can be considered as a multi-layer optical storage media (like a DVD disk) with the storage capacity of about 1 Tb/100 cm 2 (images level without data reduction) The mean area to be scanned is ~200 cm 2 per each OPERA event Considering 20000 events to process the full area to be scanned is 400 m 2 of the emulsion surface With the old manual scanning the total tracks search in a wide angular range was difficult. The human scanning performance for this kind of data is less then 1 mm 2 /hour So if an experienced operator decides to analyze manually the full OPERA data it would takes him about 40000 years

17. Emulsion data reconstruction V. Tioukov QFTHEP11, Sochi 1.Track following: TT->CS-Brick upstream till the vertex 2.Volume scan and reconstruction of all tracks around the expected vertex position All segments Long tracks: after alignment and tracking Vertex found

18. V. Tioukov QFTHEP11, Sochi In spring 2010 OPERA present the first   candidate base on the analysis of 35% of ‘08/’09 statistics. Data selection was done using the cuts defined at the time experimental proposal (2001) The first tau candidate

19. V. Tioukov QFTHEP11, Sochi beam Event ECC  pink color The viewer of scintillation Target Tracker 19

20. V. Tioukov QFTHEP11, Sochi

21. Completed (92%) the 2008-2009 data analysis = 4.8 10 19 pot Statistic 2.6 larger then previous publication Improvements in signal and background based on: –Search of highly ionizing tracks in hadronic interactions –Follow down of the tracks in the emulsion to reduce charm background searching for muons not observed by the Electronic Detector Hadronic background due to muon mismatched to hadrons –Full simulation chain with emulsion off-line reconstruction. –Better knowledge of Charm production cross section from CHORUS. Work of the last year (after the candidate detection)

22. V. Tioukov QFTHEP11, Sochi  -,e - ,e D+D+ +e+h++e+h+   h  --,   h BG reduction by the systematical tracks follow down for the candidate events to improve the muons id Charm background Hadrons re-interaction background Momentum range correlation: tested for the first  candidate event Misidentified muons from charm events: 3.28 % (was 5%) Factor 100 reduction of the BG for the τ -> µ channel: golden channel! In 95 % of cases the muon should be identified by the electronic detector But when it missed or misidentified with hadron the following topologies becomes the background:

23. V. Tioukov QFTHEP11, Sochi Hadron tracks in OPERA neutrino interactions with kink topology far from primary vertex Hadron interactions search in 4 GeV π test beam 14 m, equivalent to 2300 NC events No events found in signal region, signal boundary region (Pt>200 MeV/c):  10 events observed (10.8 events expected by updated simulation including black tracks search) Signal region Hadron re-interaction studies using the Pions test-beam data and real OPERA data

24. V. Tioukov QFTHEP11, Sochi Decay channel Number of signal events expected for  m 2 = 2.5×10 -3 eV 2 22.5×10 19 p.o.t. Analysed sample  → µ 1.790.39  → e 2.890.63  → h 2.250.49  → 3h 0.710.15 Total 7.631.65 In the analyzed sample (92% of ‘08+’09 data) one  observed in the  h channel compatible with the expectation of 1.65 signal events. Including all the improvements in the analysis Expected OPERA signal

25. V. Tioukov QFTHEP11, Sochi Decay channel Number of background events for: 22.5×10 19 p.o.t.Analysed sample CharmHadronMuonTotalCharmHadronMuonTotal  → µ 0.0250.000.070.09±0.040.00 0.020.02±0.01  → e 0.22000.22±0.050.05000.05±0.01  → h 0.140.1100.24±0.060.030.0200.05±0.01  → 3h 0.18000.18±0.040.04000.04±0.01 Total 0.550.110.070.73±0.150.120.02 0.16±0.03 Background summary Production and decay of charmed particles Hadrons re-interactions Muons scattering on the big angle

26. V. Tioukov QFTHEP11, Sochi 3765 interactions located, 3289 “decay searched” events OPERA events interaction, bricks extraction and processing rates 2008 2009 2010 2011

27. V. Tioukov QFTHEP11, Sochi Other interesting events: nue so far detected 20 nu-e events as the byproduct of nu-tau search Developed the dedicated strategy for nu-e search to increase the detection efficiency Estimation of the background in progress: prompt nu-e and gamma conversion contamination

28. V. Tioukov QFTHEP11, Sochi Summary for the peculiar topologies found Events Located Decay search Charm Candidates e  candidates Total3765328952201

29. V. Tioukov QFTHEP11, Sochi Neutrino velocity measurement in OPERA ● LBL (730 km) neutrino experiment with is well suited for this kind of test ● Velocity = distance/time = (x2 - x1) / (t2 - t1) we need to know start point and end point with the 10 cm accuracy and the start time and finish time with 5 ns accuracy for this measurement in the global Reference System ● Using the GPS technique it is possible to know the global coordinate of the reference point with the accuracy of 1 cm ● Using the GPS in a special way and the atomic clocks it is possible to synchronize CERN and GS DAQ with 1 ns ● It is not possible to know the exact position of the neutrino decay point inside the decay tunnel but this do not change significantly the total travel time ● It is not possible to know the exact position inside the spill of the particular OPERA event but it is possible to make the statistical analysis if we know the exact shape of each spill.

30. OPERA sensitivity High neutrino energy - high statistics ~16000 events Sophisticated timing system: ~1 ns CNGS-OPERA synchronisation Accurate calibrations of CNGS and OPERA timing chains: ~ 1 ns level Precise measurement of neutrino time distribution at CERN through proton waveforms Measurement of baseline by global geodesy: 20 cm accuracy over 730 km  Result: ~10 ns overall accuracy on TOF with similar stat. and sys. errors V. Tioukov QFTHEP11, Sochi

31. Summary of the principle for the TOF measurement Measure  t =TOF c - TOF 31 z y x V. Tioukov QFTHEP11, Sochi

32. Time-link created between Tx LNGS and Tx CERN updated every second GPS and common view mode  Data of the satellites seen simultaneously selected offline, ionospheric free P3 code used  Delay of the Cs clock with respect to the GPS observation computed internally by the GPS receiver (RefC, RefG) V. Tioukov QFTHEP11, Sochi

33. The analysis of data from the 2009, 2010 and 2011 CNGS runs was carried out to measure the neutrino time of flight. For CNGS muon neutrinos travelling through the Earth’s crust with an average energy of 17 GeV the results of the analysis indicate an early neutrino arrival time with respect to the one computed by assuming the speed of light: δt = TOF c -TOF n = (60.7 ± 6.9 (stat.) ± 7.4 (sys.)) ns We cannot explain the observed effect in terms of known systematic uncertainties. Therefore, the measurement indicates a neutrino velocity higher than the speed of light: (v-c)/c = δt /(TOF c - δt) = (2.48 ± 0.28 (stat.) ± 0.30 (sys.)) ×10 -5 with an overall significance of 6.0 σ. Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to identify any still unknown systematic effect. We do not attempt any theoretical or phenomenological interpretation of the results. V. Tioukov QFTHEP11, Sochi

34. Summary and outlook The Collaboration has completed the study of the neutrino data taken in the CNGS beam in the 2008-2009 runs One muonless event showing a  → 1 -prong hadron decay topology has been detected and studied in details. It passes all kinematical cuts required to reduce the physics background   The observation so far of a single   candidate event is compatible with the expectation of 1.65 signal events. The significance of the observation of one decay in the  → h channel is 95% Our expectation is to collect by the end of 2012 a total statistics (2008-2012) as close as possible to the goal of the experiment: of 22.5x1019 p.o.t.  eThe main physics goal remains the statistically significant observation of direct appearance  -  flavor transition, as well as of the study of the sub- leading  - e oscillation In the coming months will be done the extensive campaign for crosschecking and additional systematic errors study for the neutrino velocity measurement