Observation of ν μ → ν τ oscillations in the CNGS beam with the OPERA experiment M. De Serio...

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Transcript of Observation of ν μ → ν τ oscillations in the CNGS beam with the OPERA experiment M. De Serio...

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Observation of oscillations in the CNGS beam with the OPERA experiment M. De Serio University of Bari & INFN Bari On behalf of the OPERA Collaboration 3 rd International Conference of New Frontiers in Physics - Kolymbari, Crete Slide 2 M. De Serio - ICNFP 20142 Observation of oscillations in the CNGS beam with the OPERA experiment The OPERA experiment Physics motivation detection principle Detector Analysis chain Status of data analysis oscillation results Other physics results Slide 3 The OPERA Collaboration M. De Serio - ICNFP 20143 About 140 physicists from 28 institutions http://operaweb.lngs.infn.it Belgium IIHE-ULB Brussels Croatia IRB Zagreb France LAPP Annecy IPHC Strasbourg Germany Hamburg Israel Technion Haifa Italy Bari Bologna Frascati LAquila LNGS Naples Padova Rome Salerno Japan Aichi Toho Kobe Nagoya Utsunomiya Russia INR RAS Moscow LPI RAS Moscow ITEP Moscow SINP MSU Moscow JINR Dubna Switzerland Bern Turkey METU Ankara Korea Jinju Slide 4 M. De Serio - ICNFP 20144 Neutrino oscillation appearance Neutrino oscillation in the atmospheric sector established in 1998 in disappearance mode (SuperKamiokande, MACRO, ) Oscillation mechanism later confirmed by accelerator experiments (K2K, MINOS) as well as solar neutrino experiments (KamLAND, SNO, Borexino, ) Oscillated neutrino appearance: a missing tile in the picture. OPERA designed to observe appearance in a pure beam. Requirements: High neutrino energy High beam intensity Large target mass Long baseline Detector capability to identify short-lived lepton Slide 5 M. De Serio - ICNFP 20145 Oscillation Project with Emulsion tRacking Apparatus L = 732 km CERN LNGS Cern Neutrinos to Gran Sasso beam High-energy beam ( ) optimised to maximise interactions at LNGS Gran Sasso National Laboratory: 1400 m rock shield (cosmic flux reduction ~ 10 -6 ) Slide 6 M. De Serio - ICNFP 20146 Decay kink -- oscillation -, h -, e - (+ 3h) -- detection signature Detection of s from oscillation in a sea of interactions through the observation of decays into muon, electron and hadron(s): Target mass O(kt) (small interaction cross-section) High granularity detector ( decay detection, background rejection) appearance on event-by-event basis Slide 7 M. De Serio - ICNFP 20147 OPERA detector SUPERMODULE 1SUPERMODULE 2 Hall C Laboratori Nazionali Gran Sasso CNGS Beam Muon spectrometer dipolar magnet instrumented with RPCs and drift tubes Target section walls of lead nuclear emulsion bricks interfaced with planes of plastic scintillator strips (Target Tracker, TT) Veto Muon ID, momentum and charge measurement Event trigger and brick finding Slide 8 M. De Serio - ICNFP 20148 OPERA detector SUPERMODULE 1SUPERMODULE 2 Hall C Laboratori Nazionali Gran Sasso CNGS Beam Muon spectrometer dipolar magnet instrumented with RPCs and drift tubes Target section walls of lead nuclear emulsion bricks interfaced with planes of plastic scintillator strips (Target Trackers, TT) Veto id efficiency 95% (with TT) p/p < 20%, p < 50 GeV/c misidentified charge prob. : 1.2% Trigger efficiency > 99% Brick finding : 60 80% Slide 9 M. De Serio - ICNFP 20149 OPERA detector 6 m 150,000 bricks (total target mass ~ 1.25 kt) arranged in 62 walls Changeable Sheets (CS) Changeable Sheets (CS): 2 nuclear emulsion films in a removable box glued on the downstream face of the brick acting as an interface between TT and brick Brick Brick: 57 nuclear emulsion films interleaved with 56 lead plates (1mm thick) 12.5cm 10.2cm 10 mm 25 mrad TT - CS 60 m 10 mrad CS - brick Slide 10 M. De Serio - ICNFP 201410 From ED data analysis, a brick probability map is built. The brick with the highest probability is extracted from the target. First interaction reconstructed in OPERA target (2007) Event location strategy Slide 11 M. De Serio - ICNFP 201411 Event location strategy Analysis of CS confirmation of interaction, predictions for brick analysis Track following in the brick film by film up to disappearance point High-energy cosmic rays used for film inter-calibration Micrometric resolution achieved in track and vertex reconstruction JHEP 11 (2013) 036 Location efficiency vs event energy Impact parameter of tracks w.r.t. reconstructed interaction vertices Slide 12 M. De Serio - ICNFP 201412 Decay search strategy Decay confirmation benefits of : Momentum measurement by Multiple Coulomb Scattering E.m. shower detection and energy measurement Detection of highly-ionizing nuclear fragments (discrimination between interactions and decays) Impact parameter crucial to detect decay daughters Details will be given in A. Pastores talk this afternoon Impact parameter vs. longitudinal distance from reconstructed interaction vertex Slide 13 M. De Serio - ICNFP 201413 Search for short-lived particle decays: charmed hadrons as control sample Charmed hadrons have masses and lifetimes similar to those of the lepton: powerful tool to directly test detection efficiency 50 events observed in the sample 2008 2010 54 4 events expected arXiv1404.4357 Accepted for publication in EPJC Details will be given in A. Pastores talk this afternoon Slide 14 M. De Serio - ICNFP 201414 Runp.o.t. (10 19 ) SPS efficiency Beam days interactions 20081.761%1231931 20093.5373%1554005 20104.0980%1874515 20114.7579%2435131 20123.8682%2573923 Total17.9777%96519505 Status of the analysis 1.18 kt on average 80% of the expected intensity Analysis strategy Runs 2008 2009: 1 st and 2 nd most probable bricks analysed Runs 2010 2012: 1 st brick only analysed so far. Extension to less probable bricks in progress. Slide 15 M. De Serio - ICNFP 201415 oscillation analysis Data sample: 4685 located and fully analysed interactions Expected events: 2.1 0.4 ( m 2 = 2.32 x 10 -3 eV 2, 23 = /4 ) Observed events: 4 Slide 16 M. De Serio - ICNFP 201416 The first candidate event Physics Letters B 691 (2010) 138 First direct detection of oscillations in appearance mode VariableValue Kink angle (mrad)41 2 Decay length (m)1335 35 P daughter (GeV/c)12 +6 -3 Pt (MeV/c)470 +230 -120 Missing Pt at 1ry vertex (MeV/c) 570 +320 -170 (deg) 173 2 0 - 0 Slide 17 2000 m M. De Serio - ICNFP 201417 The second candidate event Journal of High Energy Physics 11 (2013) 036 - h - h - h + candidate decay in plastic base Flight length: 1.54 mm Slide 18 M. De Serio - ICNFP 201418 The third candidate event First measurement of the lepton charge in appearance mode Phys. Rev. D 89 (2014) 051102(R) - - Muon momentum: by range (electronic detectors) 2.8 0.2 GeV/c by MCS in emulsion 3.1 [2.6, 4.0] GeV/c Slide 19 M. De Serio - ICNFP 201419 The fourth candidate event arXiv 1407.3513 - Submitted to PTEP Slide 20 The fourth candidate event M. De Serio - ICNFP 201420 All tracks attached to the reconstructed interaction have been followed in downstream bricks in order to check the compatibility with the muon hypothesis. Track 2 crosses 9 wall and stops in the spectrometer; not compatible with hypothesis based on momentum range correlation Track 3: visible interaction in downstream brick #2 Track 4 crosses 1 wall; identified as a proton based on its ionization Slide 21 M. De Serio - ICNFP 201421 The fourth candidate event Slide 22 Expected events after completion of 2 nd bricks for 2010 2012 runs: 3.2 events M. De Serio - ICNFP 201422 oscillation analysis summary Not yet accounted for: foreseen extension of the analysis to 3rd and 4th bricks in the probability map (~ 20% effect ) Visible energy in emulsion 1 st candidate 3 rd candidate 4 th candidate 2 nd candidate Slide 23 Expected events after completion of 2 nd bricks for 2010 2012 runs: 3.2 events M. De Serio - ICNFP 201423 oscillation analysis summary Not yet accounted for: foreseen extension of the analysis to 3rd and 4th bricks in the probability map (~ 20% effect ) Decay channel Expected signal m 23 2 = 2.32 meV 2 Total background Observed h 0.41 0.080.033 0.0062 3h 0.57 0.110.155 0.0301 0.52 0.100.018 0.0071 e 0.62 0.120.027 0.0050 Total2.11 0.420.233 0.0414 Two statistical methods Fisher combination of single channel p-values Likelihood ratio 4.2 significance of null observation Observation of appearance Slide 24 M. De Serio - ICNFP 201424 oscillation analysis OPERA Preliminary (tau appearance) ANTARES (atm. neutrino) MINOS (pure atm. anti-nu) MINOS (anti-nu beam) MINOS (pure atm. nu) MINOS (atmospheric) T2K MINOS (2, maximal mixing) First measurement of m 2 23 with appearance 90% CL intervals on m 2 32 assuming sin 2 (2 23 ) = 1 Feldman & Cousin [1.8 5] x 10 -3 eV 2 Bayesian [1.9 5] x 10 -3 eV 2 OPERA Off-peak L/ ~ 43 Km/GeV (L/ ) peak ~ 500 Km/GeV Slide 25 M. De Serio - ICNFP 201425 e oscillation results e events searched for in a sample of 505 neutrino interactions without muon in the final state (runs 2008-2009). Extension to full statistics in progress. 19 (4) events observed, 19.8 2.8 (4.6) events expected (E