Recent results of OPERA experiment T. Shiraishi - Nagoya University On behalf of The OPERA Collaboration 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 Nihon Israel Technion Haifa Korea Jinju Russia INR RAS Moscow LPI RAS Moscow ITEP Moscow SINP MSU Moscow JINR Dubna Switzerland Bern Turkey METU Ankara 140 physicists, 28 institutions in 11 countries 1

 →  oscillation in appearance SK’s observation of the atmospheric neutrino disappearance indicated neutrino oscillation The oscillation analyses have been mostly done in disappearance OPERA is designed to observe  →  oscillation through  appearance 2

CNGS (CERN Neutrino to Gran Sasso) CERN SPS 732km Pure   Appearance  3 /17 OPERA Gran Sasso High energy neutrino (above 3.5 GeV) Long baseline Optimized to maximize tau neutrino interaction Oscillation Prob * Cross Section

Principle of tau neutrino detection   -- No-oscillation 11% QE, 89%DIS Micrometric accuracy with large target mass ECC is the only detector which directly observed tau neutrinos in DONUT experiment decay “kink”     -,e -,h -,3h Oscillation 35% QE, 65%DIS c  ~ 87  m (~ IP) Path ~ 600  m 8.3 kg, 10 Radiation Length 7.5 cm 12.5 cm 10 cm beam ECC (Emulsion Cloud Chamber) : OPERA main detector 57 emulsion films 56 lead plates 4

OPERA detector Target areaMuon spectrometer (Drift Tube + RPC + Magnet) 150,000 ECC bricks = 1.25 kton target mass 1.0cm Scintillator strips Target Tracker (TT) Doublet of emulsion films Gran Sasso UnderGround 1,400m (3,800 m.w.e)

Vertex Location and Decay Search TTCS ECC leademulsion 2.6 cm Reconstruction All candidates of tracks 1cm 2 ×10plate volume scan Tracks remaining after taking multi layers’ coincidence After rejection of tracks penetrating the volume Japan (S-UTS)Europe (ESS) Scanning speed : 75cm 2 /h x 5 system 20cm 2 /h x 10 system Tracking to the vertex Vertex Raw data Search for large IP tracks (Decay Search) Scanning system 6

Analysis status 7 Data Sample Run Analysis strategy is 1st and 2nd probable bricks 1st 2nd ~10% remained  These will be done until July 2015

Event selection Kinematical cuts Background beam transverse plane Parent vector Other visible vectors  angle Neutrino vertex 8  MC charm MC In decreasing order  distribution  : large  Charm : small 

9 Efficiency control sample Charm decay has similar topology as tau decay Muon attached to the interaction point  + n   + D + p + (anything) Good agreement between data and MC Eur. Phys. J. C (2014) 74: 2986

4 tau neutrino events τ − →ρ − ν τ ρ − →π 0 π - π 0 → γ γ 1 st  τ -> 3h τ ->  τ  ->    2 nd  3 rd  τ -> h 4 th  4 th  paper has been accepted by PTEP JHEP 1311 (2013) 036 Phys.Rev. D89 (2014) τ -> h 10 arXiv : v2 Phys.Lett. B691 (2010)

Summary of 4 tau neutrino events Visible energy (Scalar sum of momenta and  energies)  angle 11 2 nd 1 st 3 rd 4 th

P value = 1.03 x  No oscillation excluded at 4.2  CL (Multivariable analysis ongoing) Oscillation analysis 12 90% CL intervals assuming sin 2 (2  )=1 Feldman&Cousin : [ 1.8, 5.0] x eV 2 Bayesien : [ 1.9, 5.0] x eV 2 The first measurement of  m 2 32 in tau neutrino appearance Decay channel Expected signal Δm 2 = 2.32x10 -3 eV 2 Total background Observed τ  h τ  h0.41± ± τ  3h0.57± ± τ  μ0.52± ± τ  e τ  e0.62± ± Total2.11± ± Details of background Charmμ scatteringHadron int 0.015± ± ± ± ± ± ± ± ± ±0.006 Combination of four single channel p-value

Non-standard oscillation model Number of observed  is a little excess, but consistent with other disappearance results in standard 3 flavors model LSND indicated existence of 3rd  m 2 (4th neutrino) eV 2 7.6×10 -5 eV 2, 2.4×10 -3 eV 2, eV 2 Number of observed  depends on the oscillation model (standard 3 flavors, 3+1, 3+2 …) Limiting the non-standard oscillation (ex. 3+1 model) 13

Sterile neutrinos OPERA allowed region Koop et al. JHEP 1305 (2013) 050 OPERA 14  appearance in the presence of sterile neutrino (3+1) Preliminary log scal

Sterile neutrinos OPERA 15 Preliminary  appearance in the presence of sterile neutrino (3+1)

OPERA analyses 16 Oscillation analysis    in appearance OPERA can also see other oscillations   e in appearance 19 e events have been reported from 2008~2009 data sample JHEP 1307 (2013) 004 They are consistent with prompt e This analysis will be extended to 2010~2012 data sample    disappearance Measurement of TeV atmospheric muon charge ratio Eur.Phys.J. C74 (2014) 2933 Study of hadron interactions PTEP 2014 (2014) 093C01 Cosmic ray events analysis OPERA detector has also recorded cosmic ray events No other detectors achieve such the coexistence of micro-metric tracking accuracy and large target mass Atmospheric neutrinos analysis Exotic events search (such as unsolved Kolar events [ref. Phys. Lett. B57 (1978) ] )

Conclusion The achievement of main analysis is about 90%. In them, 4  events have been found. The significance for the  →  oscillation in appearance is 4.2 . The  m 2 32 is consistent with other disappearance results. Analyzing limitation the non-standard oscillation, preliminary Some other analyses ongoing 17

Backup 18

Summary of 4 tau neutrino events  → h  → 3h  →   →  →   → h  → 3h  →   → h  →   → h  → 3h  → h  → 3h  →   → h  → 3h  → h  →  19

Marginal events analysis ongoing 大体 2 倍ぐらいシグナル増える 20

 →  e  oscillation analysis ongoing Run sample 19 事象同定（ prompt e コンシステント） → JHEP 1307 (2013) 004 現在全サンプルを対象に探索中 45 事象同定 update したサンプルで次の結果を出す。 21 ３種類のニュートリノ フレーバーと NC 反応を 決定できる。 原子核乾板での分解能 により π 0 と e 反応を区別可能。 BG ~ 1% (0.2 個 19  e 中 )

POT and Target Mass 22

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Prompt  25

Charmed mesons creation 26

 leptons creation 実験室系重心系 27