Recent result in the OPERA experiment

1. Recent result in the OPERA experiment K.Ishiguro ( Nagoya ) for the Opera collaboration

2. goal of the OPERA experiment OPERA first tau neutrino cand ・not yet appearance detection of neutrino oscillation is done ・ direct detection in appearance mode of mu neutrino → tau neutrino oscillation make a conclusion of existence of neutrino oscillation and neutrino mass

3. OPERA mu neutrino beam line pot(2008-2012) 17.97 x 1019 (80% of planned pot) ・Long baseline neutrino oscillation experiment in the CNGS pure nm beam ・expect to detect about 6

4. ntappearance: detection principle no other lepton at the primary vertex ・event-by-event identification of tau neutrino event topology ・need special position resolution around vertex point

5. OPERA emulsion film 50 μm OPERA emulsion film emulsion emulsion plastic base Plastic base Lead plate : 1mm 45μm Microscopic image 200μm track of charged particle position resolution : 0.3 m

6. 7.5cm 12.5cm 10radiation length 10cm 57films In a Brick ECC(emulsion cloud chamber) 100 500 1mm lead emulsion plastic emulsion n Primary vertex IP 10 6

7. The OPERA detector • ~150000 Bricks installed • muon charge and momentum measurement is done by the spectrometers • Target Tracker (TT ) to locate the event brick

8. TT hit Vertex Location ・Brick Extraction by TT hit Volume Scan 1cm^2 * 10films

9. ・location analyses is now ongoing. ・till March 2013 4725 events fully reconstructed • 2 tau neutrino candidate events found till 2012 ①　hadron kink mode event ( ) ②　3h decay mode event

10. hadron kink mode event ( )

11. 3h decay mode event 11 Giovanni De Lellis, LNGS Seminar

12. plastic hadron interuction in emulsion Giovanni De Lellis, LNGS Seminar

13. 3rd tau neutrino candidate (First τ -> μcandidate event)

14. emulsion plastic lead Decay Pt of tau Kink point Decay point :center of plastic base Kink angle: 0.245±0.005rad Decay Pt: 690±50MeV/c muon IP:93.7μm

15. Pointing primary VTX 1ry partner ,track angle tanθ< 3.0 is searched primary hadron Φ ~154.5° Phi angle 154.5°±1.5° depth : 225μm ( lead ) strong signature as a CC event

16. daughter particle muon identified by TT hits lead

17. X Negative muoncharge from track curvature in the spectrometer (RPC hits) - μ Target Tracker hits P2<0  negative charge 5.6 σ significance R ~ 85 cm B RPC hits P-value = 0.063% (probability to reconstruct a m+ stopping in the 7th iron layer with p2 < -0.00389 cm-1)

18. Primary particle TThit the primary particle is a hadron The primary particle has a measured impulsion of 0.96 -0.20 + 0.26 GeV/c. If it had been muon, it would have penetrated 14 bricks. It penetrates only one downstream brick (TT hits), it cannot be identified as a muon. By emulsion analyses, the track entered the brick in 27th film 60micron from the edge it interacted after crossing 18 emulsion films without visible charged particles

19. By emulsion analyses, the track entered the brick in 27th film 60micron from the edge it interacted after crossing 18 emulsion films without visible charged particles another timing CR ~7cm no track in downstream8 films Stopping point primary hadron In this brick cross checked by down stream 4 CSs possibility of Inefficiency by emulsion (2.7*10^-8 ) * 1.25*10^-3 ~10^-11

20. About gamma the gamma is pointing to the primary vertex (Momentum=2.64 GeV[1.9,4.3])

21. Kinematic cuts (decay Pt) Kink angle 245 ± 5 690±50 cut 20mrad cut250MeV/c Phi angle decay length Muon momentum 2.8±0.2 154.5 ± 1.5 376 ± 10

22. Statistical considerationsExtended sample to muonic interactions with the 3 candidate events, a 3.2 sigma significance by a simple counting method. (Pvalue = 1.125 x 10-4 ) since the effect of muon charge and material of decay point is not reflected, more elaborated statistical approaches with a likelyhood approach are being studied

23. Background ・muon scattering Pt distribution of the muon scattering simulation 500 100 300 700 250 690 Pt_MeV • Third event in plastic: Pt of 690MeV • muon scattering background of order 10^-8 to 10^-7.

24. Background ・Charm event If muon not identified similar topology of tau neutrino event OPERA charm event １ｒｙ mu gamma mu+ charm daughter sign is positive muon sign is negative in 3rd event  charm backGround ~ 0.0084 * 0.01 charm

25. ・Sign of muon is negative and it is detected for the first time event by event in the neutrino oscillation . ・detected neutrino after oscillation is not but ν ν μ τ ν ν detected τ μ

26. Technology of the track selector is developed through the OPERA experiment. speed up of the track selector development of Large angle track selector Hyper Track Selector scanning time for 100cm^2 film ~ 5minutes proposal used for background reduction by large angle 1ry muon search fragment search from decay point will start OPERA film scanning from this Summer

27. ○　Another timing events are also recorded in the OPERA detector. ・atmospheric neutrino oscillation ・ CR event analyses What’s next with new technology

28. Conclusion ・till March 2013 4725 events fully reconstructed ・3rd event is detected in muonic decay mode. ・ decay point in the plastic , decay Pt~690MeV/c  muon scattering background is negligible ・muon sign is negative  charm background is negligible. ・Conservative background evaluation with 3events Significance of 3.2σ with simple counting method ・likelyhood approach are being studied. ・detected neutrino after oscillation is not but

29. Giovanni De Lellis, LNGS Seminar

30. Status at May31. CS scanned 14737 CS found 10585 ECC scanned 9629 Located 6067 DS 4949

31. Achievement for each sample All 2010CC 2010NC 2011NC 2011CC 2012NC 2012CC

32. What’s next with new technology ○Wide area CS scaning We will end 90 % of events location In 2013.