Neutrino Oscillations in the OPERA Experiment e e e e Umut KOSE on behalf of OPERA Collaboration NUFACT2014, XVIth International Workshop on Neutrino Factories and Future Neutrino Facilities 1 University of Glasgow, 25th to 30th of August, 2014
The OPERA Collaboration 140 physicists, 28 institutions in 11 countries Korea Israel Belgium Jinju Technion Haifa IIHE-ULB Brussels Italy Russia Croatia Bari INR RAS Moscow IRB Zagreb Bologna LPI RAS Moscow LNF Frascati ITEP Moscow L’Aquila SINP MSU Moscow LNGS JINR Dubna France Naples LAPP Annecy Padova IPHC Strasbourg Switzerland Rome Bern Salerno Japan Germany Turkey Hamburg Aichi METU Ankara Toho Kobe Nagoya Nihon U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 2
Oscillation Project with Emulsion-tRacking Apparatus Aim: establish neutrino oscillations in direct appearance mode in the 𝝃 𝝂 → 𝝃 𝝊 channel at atmospheric scale, through detection of the tau lepton produced in Charged Current (CC) interaction on event-by-event basis. Full coverage of the parameter space indicated by SK, T2K and MINOS. 𝝊 lep epton de decays: 𝝊 − → 𝝂 − + 𝝃 𝝂 + 𝝃 𝝊 17.7% 𝝊 − → 𝒇 − + 𝝃 𝒇 + 𝝃 𝝊 17.8% - 𝝊 − → 𝒊𝒃𝒆𝒔𝒑𝒐 + 𝝃 𝝊 49.5% oscillation 𝝊 − → 𝝆 − 𝝆 − 𝝆 + (𝒐𝝆 𝟏 ) + 𝝃 𝝊 15.0% ~ 1 mm P( ) ~ sin 2 2 23 cos 4 13 sin 2 ( m 2 23 L/4E) Requirements: High energy and high intensity neutrino beam Conventional beam optimized for appearance Long baseline Large target mass and submicron resolution Detector capability to identify short-lived lepton U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 3
CERN Neutrino to Gran Sasso Beam http://proj-cngs.web.cern.ch/proj-cngs/ Gran Sasso National Laboratory : 1400 m rock shield (cosmic flux reduction by a factor 10 6 w.r.t. surface) LNGS CERN L = 730 km P( ) ~ 1% OPERA < 𝑭 𝝃 > 17 GeV L 730 km (𝝃 𝒇 + 𝝃 𝒇 )/𝝃 𝝂 0.87 % * 𝝃 𝝂 /𝝃 𝝂 2.1 % * 𝝃 𝝊 prompt Negligible * * Interaction rate at LNGS Optimised to maximise CC interactions at LNGS 4 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK
OPERA detector* *JINST 4 P04018, 2009. SM1 SM2 Muon Spectrometer Brick walls+Target Tracker(TT) RPC+ Drift Tubes (HPT) Veto Each brick wall followed by a plane of id efficiency 95% (with TT) Scintillator strips in X/Y direction. p/p < 20% , p < 50 GeV/c Target Tracker used for localization of Interaction brick. misidentified charge prob. : 1.2% ● Trigger efficiency > 99% ECC brick= 56 lead plates + 57 films ~8kg (10X 0 ) ● Brick finding : 60 80% U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 5
Typical CC-like and NC-like events CC CC, → (17.7%) 20 m NC CC, → e (17.8%) CC, → h, 3h (64.5%) e CC U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 6
Neutrino interaction location in ECC Step 1: CS scanning confirmation of Step 2-4: CS-ECC connection, ScanBack interaction, predictions for brick analysis procedure, Volume data taking JHEP 11 (2013) 036 Location efficiency vs event energy Step 5-6: Validation of neutrino interaction vertex U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 7
Decay search Eur. Phys. J. C 74 (2014) 2986. Impact Parameter evaluation crucial point to detect decay topology Kink search Parent search Impact parameter of tracks w.r.t. Impact parameter vs. longitudinal distance reconstructed interaction vertices from reconstructed interaction vertex U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 8
Status of the Analysis Run p.o.t. SPS Beam ν (10 19 ) efficiency days interactions 1.18 kt on average 2008 1.7 61% 123 1931 2009 3.53 73% 155 4005 2010 4.09 80% 187 4515 2011 4.75 79% 243 5131 2012 3.86 82% 257 3923 Total 17.97 77% 965 19505 80% of the design ~87% predicted in the bricks Analysis strategy Bricks ordered by the probability to contain the neutrino interaction Runs 2008-2009: 1 st and 2 nd most probable 6636 located 6190 decay search bricks Runs 2010 2012: 1 st brick analysed so far. Extension to less probable bricks in progress. 9 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK
Search for short-lived particle decays: charmed hadrons as control sample Charmed hadrons produced by CC interactions Eur. Phys. J. C 74 (2014) 2986. muon at the primary vertex Mass and lifetime charmed hadrons ~ tau lepton similar decay topology 2008-2010 OPERA data set 54 ± 4 charm events expected 50 observed in control sample Good agreement between data and MC. 10 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK
𝝃 𝝂 → 𝝃 𝒇 oscillation results JHEP 1307 (2013) 004 𝝃 𝒇 searched in 505 (data of 2008-2009 run ~ 50% full statistics) neutrino interaction without the muon in the final state. Extension to full statistic in progress. E = 15.6 GeV 𝒕𝒋𝒐 𝟑 𝟑𝜾 𝟐𝟒 < 𝟏. 𝟓𝟓 @ 90% C.L. 𝒕𝒋𝒐 𝟑 𝟑𝜾 𝒐𝒇𝒙 < 𝟖. 𝟑 × 𝟐𝟏 −𝟒 @ 90% C.L. U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 11
𝝃 𝝂 → 𝝃 𝝊 oscillation analysis Data sample: 4685 located and fully analysed interactions Kinematical selection cuts kept fixed since beginning of the experiment. Expected events: 2.1 0.4 ( m 2 = 2.32 x 10 -3 eV 2 , 23 = /4 ) Observed events: 4 After completion of 2 nd bricks for 2010 2012 runs, expected events : 3.2 events 12 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK
The first candidate event Phys. Lett. B (2010) 138 Variable Value First direct detection of oscillations 41 ± 2 Kink angle (mrad) in appearance mode 1335 ± 35 Decay length (µm) 1 2 120 ± 20 ± 35 MeV P daughter (GeV/c) 12 +6 -3 - 1 2 640 +125 +100 -90 MeV -80 470 +230 Pt (MeV/c) -120 + N - + hadrons Missing Pt at 1ry vertex 570 +320 - + -170 (MeV/c) - + 0 173 ± 2 ϕ ( deg) U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 13
The second candidate event JHEP 11 (2013) 036 2000 m + N - + hadrons h + h - h - U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 14
The third candidate event Phys. Rev. D 89 (2014) 051102(R) → 𝑪 + N - + hadrons - Muon momentum: by range (electronic detectors) 2.8 0.2 GeV/c by MCS in emulsion 3.1 [2.6, 4.0] GeV/c Negative muon measured in the muon spectrometer First measurement of the lepton charge in appearance mode 15 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK
The fourth candidate event arXiv 1407.3513 - Submitted to PTEP Track 3 visible interaction in downstream brick #2 Track 4 crosses 1 wall; identified as a proton based on its ionization + N - + hadrons Track 2 from neutrino - interaction vertex, p = 1.9 GeV crossing 9 wall and stopping in first iron slab of the magnet. 0.35% 9.2% U. Kose, Nufact2014, 25-30 August 2014, 16 Glasgow, UK
Summary of four events Visible energy of all 𝝃 𝝊 events: Scalar sum of momentum and energies Candidate Decay Mode Psum(GeV/c) year +𝟕.𝟐 𝝊 → 𝒊 𝟑𝟓. 𝟒 −𝟒.𝟑 1 st 2010 +𝟑.𝟒 𝝊 → 𝟒𝒊 𝟐𝟑. 𝟖 −𝟐.𝟖 2 nd 2012 𝝊 → 𝝂 − +𝟏.𝟘 𝟕. 𝟗 −𝟏.𝟕 3 rd 2013 +𝟒.𝟘 𝝊 → 𝒊 𝟐𝟓. 𝟓 −𝟑.𝟖 4 th 2014 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 17
Significance The expected signal and background is normalized to the number of located events Decay Expected signal Total Observed 2 = 2.32 meV 2 channel Δ m 23 background h 0.41 ± 0.08 0.033 ± 0.006 2 3h 0.57 ± 0.11 0.155 ± 0.030 1 0.52 ± 0.10 0.018 ± 0.007 1 e 0.62 ± 0.12 0.027 ± 0.005 0 2.11 ± 0.42 0.233 ± 0.041 Total 4 Two statistical methods Fisher combination of single channel p-value = 𝟐. 𝟑𝟓 × 𝟐𝟏 −𝟔 Likelihood ratio p-value = 𝟐. 𝟏𝟒 × 𝟐𝟏 −𝟔 Observation of tau appearance with 4.2 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK 18
𝟑 in appearance experiment First measurement of ∆𝒏 𝟒𝟑 OPERA Off-peak L/<E> ~ 43 Km/GeV (L/<E>) peak ~ 500 Km/GeV Strong dependence on ∆𝒏 𝟑 measure ∆𝒏 𝟑 with counting experiment 𝟑 assuming 𝒕𝒋𝒐 𝟑 𝟑𝜾 𝟑𝟒 = 𝟐 90% CL intervals on ∆𝒏 𝟒𝟑 OPERA Preliminary (tau appearance) Feldman & Cousin ANTARES (atm. neutrino) MINOS (pure atm. anti-nu) [1.8 – 5] x 10 -3 eV 2 MINOS (anti-nu beam) Bayesian MINOS (pure atm. nu) [1.9 – 5] x 10 -3 eV 2 MINOS (atmospheric) T2K MINOS (2ν, maximal mixing) 19 U. Kose, Nufact2014, 25-30 August 2014, Glasgow, UK
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