1 Recent results on the observation of    oscillation in the OPERA experiment NakatsukaYuji Nagoya University On behalf of OPERA collaboration ICISE Qui Nhon 2013 Aug 14 Rencontres du Vietnam Windows on the Universe Belgium ULB Brussels Croatia IRB Zagreb France LAPP Annecy IPHC Strasbourg Germany Hamburg Italy Bari Bologna LNF Frascati L’Aquila LNGS Naples Padova Rome Salerno Japan Aichi edu. Kobe Nagoya Toho Utsunomiya Israel Technion Haifa Korea Jinju Russia INR RAS Moscow LPI RAS Moscow ITEP Moscow SINP MSU Moscow JINR Dubna Switzerland Bern ETH Zurich Turkey METU Ankara

2 Aim and Principle Direct detection of    oscillation   -- decay “kink”   ~1 mm  oscillation --, h -, e - plus 3-prong decay modes Observation of neutrino oscillations in appearance mode through the    channel. Aim : Principle of OPERA Experiment :

3 LNGS ( GeV ) 17 ( e + e ) /  0.89, 0.06 %  /  2.1 %  prompt Negligible Covers the region indicated by Super-K, K2K & MINOS CNGS Beam sin 2 2θ 23 = 1.0 ， Δm 23 2 = (2.43±0.13)×10 -3 eV 2 [ Phys.Rev.Lett.101:131802,2008.] 732km

4 Target Mass ~1.2ktonMuon SpectrometerTarget Super-Module The OPERA detector ~1400m

5 Typical NC-like event ECC selection 12.5cm 10cm 7.5cm 8.3kg Neutrino Beam (vertical to films) Emulsion Cloud Chamber (ECC) Stack of 57 emulsion films, 56 lead plates (10X 0 ). ~150,000 ECC installed in the OPERA detector 20 m Pb 1mm Changeable Sheet (CS) Interface emulsion films for ECC selection and track connection.

6 6 ECC Large area ~100 cm 2 Point scan ~100x100  m 2 Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion neutrino CS TT hit TT hit Vertex plate Follow back in the ECC tracks found in CS until they disappear: vertex plate 14 Event location in ECC

7 AgBr Crystal 200nm 10GeV π - M.I.P. ~30 developed silver grains / 100  m M.I.P. track 20μm A compton track Fog 125mm 100 mm OPERA Film 210um plastic base 44um emulsion

8 Event reconstruction Scanning speed/system: 75cm 2 /h *High speed CCD camera (3 kHz) *Piezo-controlled objective lens *FPGA Hard-coded algorithms European Scanning System (ESS) Japanese Scanning System (S-UTS) Scanning speed/system: 20cm 2 /h *Customized commercial Optics and mechanics *Asynchronous DAQ software All track data ~ 1cm x 1cm Required plate-plate connectionTracks converge to vertex point

9 1mm Pb Primary vertex Decay point Long flight decay  IP 1mm Pb  Primary vertex Decay point Short flight decay  IP (Mean  m) Kink  → e- → e ％  → μ- → μ ％  → h- → h ％ Trident   → h - h - h ％  decay mode    events (MC) NC+CC  events (MC) NC+CC  events (Data) Impact Parameter distribution 10  m ↔ (c  = 87  m) Without muon  CC detection Short : Long ~ 2:8

10  candidate events 1 st  candidate  -> 1h, May 2010        2nd  candidate  -> 3h, June 2012

11 μm The 3 rd  candidate event :  decay mode

12 Event Display 2.8 GeV muon

13 Event analysis Kink Angle (mrad) 245±5 Decay Length (  m) 376±10 P (Gev/c)2.8±0.2 Decay Pt (Mev/c) 690±50 Phi Angle (degrees) 154.5±1.5 pp p h total pri. h e-pair  ° beam transverse plane

14 τ→μ MC τ→μ candidate excluded region Passed all cuts of  decay criteria

15 Muon sign Spectrometer 4hits curvature radius ~ 85cm muon charge is negative 5.6  Target tracker hits 1.55T     identification of oscillated  interaction (≠  )

16 BG1 : Charm Decay Charm BG The same topology   decay  -eh-eh the decay muon charge is plus. charm decay charm   miss id

17 BG2 : Muon Large Angle Scattering Pb Film kink point Tranverse momentum PDF P T (MeV/c) 690MeV/c at base muon quark Scattering probability is proportional to the amount of material. Pb : film (emulsion + plastic base) : Upper limit : Proposal Value (S.A. Akimenko et at al, NIM A ) Prob Kink Angle (mrad)245±5 Decay Pt (Mev/c)690±50

18 Summary of    search status Three  candidates have been found, 1st :  h, 2nd :  3h, 3rd :  . The 3rd  event is pure  channel with low background and tagged as  by its muon sign. Probability explained by only background ~ 7.29 x The singnificance value : counting method : 3.2  of non-null observation, likelihood approach : 3.5  SignalBackgroundCharm  scattering had int  h  h   3h      e   e total

19 Conclusions and Prospects OPERA ran on the CNGS beam successfully , 17.97x10 19 POT, ~80 % of proposal value of CNGS beam Analysis stasus : completed 2008, 2009 events events are on going, main part (1 st ECC) will finish in Three  candidates have been found, counting method 3.2  of non-null observation, likelihood approach : 3.5  Searches are on going for more interesting events, within reach 4  observation.

20 backup

21 Charm Decay Event Candidates

22

23 Beam exposure and analysis status Beam: 5 years (965days) 17.97×10 19 p.o.t. Overall 80% of the proposal value (22.5×10 19 p.o.t.) Completed: 2008, on going with optimised strategy (ALL NC-like events and CC-like events with  momentum < 15GeV/c) ‘08‘09‘10‘11‘12 date Run 2008 → 2012 date Located 6211 CS found ECC scanned 9981 CS scanned DS 5036 (13 Jul 28)

24 The first  “ appearance ” candidate (2010) Candidate  interaction and  decay from    oscillation

25 First tau neutrino candidate event Muonless event , taken on 22 nd August 2009 (as seen by the electronic detectors) G. De Lellis - Fermilab - 4 June 2010

26 Event reconstruction in the brick  − →  −    − →        →  

27 11 1mm lead PL19PL20PL21PL17PL18 kink point Primary vertex careful visual inspection of the films behind/in front of the secondary vertex: no “black” or “evaporation” tracks. Support topological hypothesis of a particle decay

28 Kinematical variables VARIABLEAVERAGE kink (mrad)41 ± 2 decay length (  m) 1335 ± 35 P daughter (GeV/c) Pt (MeV/c) missing Pt (MeV/c) ϕ (deg) 173 ± 2 Kinematical variables are computed by averaging the two independent sets of measurements  1 and  2 both attached to 2 ry vertex

29 Second neutrino tau candidate event taken on 23 rd April 2011 as seen by the electronic detector event display

30 animation Second  Candidate Event  m

31 Schematics of the event Φ Beam View Φ=167 o Secondary Interaction In Emulsion With four Nuclear fragments

32 Zoom of the primary interaction and decay region Decay point In Plastic Base No Nuclear fragment Flight length 1.54mm

33 Track#Momentum （ 1σ interval ） [ GeV/c] Particle ID Method / Comments Primary2.8 ( ) Hadron Momentum-Range Consistency Check Stops after 2 brick walls. Incompatible with muon ( 26  44 brick walls) d1 6.6 （ ） Hadron Momentum-Range Consistency Check d2 1.3 （ ） Hadron Momentum-Range Consistency Check d32.0 ( ) HadronInteraction in the 1.3cm downstream Momentum measurement and particle identification of event tracks Independent momentum measurements carried out in two labs

34 Kinematics of the second Candidate Event CutValue φ (Tau - Hadron) [degree] > ±1.1 average kink angle [mrad] < ±1.5 Total momentum at 2ry vtx [GeV/c] > ±1.7 Min Invariant mass [GeV/c 2 ] 0.5 < < ±0.13 Invariant mass [GeV/c 2 ] 0.5 < < ±0.12 Transverse Momentum at 1ry vtx [GeV/c] < ±0.11

35 candidate cut Satisfying the criteria for ν τ    3hadron decay Kinematics of the second candidate event

36 Analysis of the interface films Sign of electromagnetic shower μ track

37 Third tau neutrino event τ  μ μm

38 Event tracks’ features TRACK NUMBERPIDMEASUREMENT 1MEASUREMENT 2 Θ X ΘYΘY P (GeV/c) Θ X ΘYΘY P (GeV/c) 1 DAUGHTER MUON [2.6,4.0]MCS ±0.2 Range (TT+RPC) 2 HADRON Range [0.70,1.10] [0.76,1.22] 3PHOTON [1.9,4.3] [2.52,4.55] 4 PARENT TAU γ attachment

39 Muon charge and momentum reconstruction Bending by the magnetic field Muon momentum by range in the electronic detector: 2.8±0.2 GeV/c MCS in the brick consistent 3.1 [2.6,4.0] GeV/c Cells ϑ (mrad)

40 Track follow down to assess the nature of track 2 Momentum/range inconsistent with μ hypothesis 0.9 GeV/4 cm Lead Track 2 interacting in the downstream brick without visible charged particles Hadrons and muon stopping in the brick track value cut value L = track length R lead = µ range ρ average = average density ρ lead = lead density p = momentum in emulsion D variable

41 THE MAGNETIC SPECTROMETERS 1.55 T magnetic field bending particles in the horizontal plane 24 slabs of magnetized iron interleaved with 24 RPC planes 6 drift tube stations for precision measurement of the angular deflection momentum resolution: 20% below 30 GeV

42 µ → e analysis 4.1 GeV electron ≈ 30 events found in the analyzed sample

43 Electron neutrino search in 2008 and 2009 runs: one of the ν e events with a π 0 as seen in the brick Interface films 19 candidates found in a sample of 505 neutrino interactions without muon

44 Background from µ NC (  0 →  ) A close-up of an electron pair 1micron Gamma-ray BG: 0.17 events (less than 1%)

45 Observation compatible with background-only hypothesis: 19.8±2.8 (syst) events 3 flavour analysis Energy cut to increase the S/N 4 observed events 4.6 expected ⇒ sin 2 (2θ 13 )<0.44 at 90% C.L. Energy distribution of the 19 νe candidates

46 Search for non-standard oscillations at large Δm 2 values: exclusion plot in the sin 2 (2θ new ) - Δm 2 new plane arXiv: Caveat: experiments with different L/E values Submitted to JHEP

47 Background estimation (hadron) 47 10GeV/c 4GeV/c 2GeV/c Multiplicity Kink angle (1-prong) nuclear fragments in emulsion 4GeV/c 2GeV/c Multiplicity Emission angle(cos  ) 10GeV/c MC:  < 0.7 ForwardBackward ForwardBackwardForwardBackward We confirmed MC simulation estimation of hadron backgrounds by using the data analysis of ECC bricks exposed to 2GeV/c, 4 GeV/c and 10GeV/c pion beams and reduced systematic uncertainty. Error bars : Experimental data Histogram : Simulated data Secondary track emission: 30% nuclear fragments:10% Nuclear fragment associated probability 2 10GeV/c 4 Hadronic background was reduced by “40%” by requiring no association of large angle nuclear fragments. 100% 0% ° 0°180° 0° 180° 0° ・ data - MC New technique for background reduction They argee well Well reproduced by MC

48 Track recognition method Take 16 tomographic images by microscope optics. Shift images to aim at specific angle tracks. Sum up 16 images to examine coincidence. Find signal of tracks. Repeat for all angles in space, >2000 times Invented by K.Niwa in 1974