More results from the OPERA experiment

1. More results from the OPERA experiment Chiara Sirignano on behalf of the OPERA Collaboration Padova University & INFN

2. 730 Km tdecay kink t ~ 1 mm nt Oscillation Project with Emulsion tRackingApparatus 75.4mm 125mm 1 mm • Long baseline neutrino oscillation experiment • CNGSquasi – pure wide band nmbeam • <E> = 17 GeV optimized to maximizen t CC interactions • Nuclear emulsions + Lead ( 150 000 ECC bricks) “active target”, • allowing 3D particle reconstruction, sub-micron spatial resolution and high background rejection rate. • More than 18 000 neutrino interactions collected in 5 years • More than 7000 nm interactions fully reconstructed and studied • Detection of 5  CC interaction by a full reconstruction of the primary vertex andobservation of tlepton decay topologies (PRL 115 (2015) 121802) Changeable interface film (CS)  t 8.3kg 10X0 Pb  beam 100mm Reconstruction Signal Detector 57 × 2 emulsion layers (42 m thick) poured on a 200m plastic base

3. SM1 SM2 • Extract Brick and CS, scan CS. • Confirm the event in the ECC brick. • Develop the brick and send films to scanning labs.  Target area : (ECC + CS + planes of scintillator strips) Muon spectrometer (Magnet+RPC+PT) Brick Manipulator System ~ 150.000 bricks 1.25 ktmass

4. • New generation automatic emulsion scanning systems • Scanning speed/system > 20cm2/h •Customizedcommercialopticsandmechanics •Customized DAQ & eventreconstructionsoftware • ~ 0.3 m spatial resolution • ~ 2 mrad angular resolution • ~ 95% detection efficiency on a single emulsion film Neutrino interactionreconstructionchain ntinteraction and tdecay

5. Eventsselection with looserkinematicalcuts Selection criteria where modified to increase the statistics and multivariate analysis was applied to select new interesting events Preliminary • 5 more  candidates • S/B reduced from 10 to 3 • Improvement in Dm223 measurement, the • first ever in appearance mode Golden events

6. Preliminary 5.2 ssignificance 6

7. Muon-lessevent 114301850 Zoom of the interactionregion : pinkbrickselected • Twosecondaryverticesreconstructed in emulsion : • short twoprong (F.L. = 103 mm) • chargedoneprong (kink) (F.L.= 1174 mm, qk = 97mrad)

8. Eventinterpretation • Twopossible rare processes: • a) n NC + cc (only 3 events in CHORUS) • b) ntCC + charm ( neverobserved) • and possible backgrounds : • ntCC + hadroninteraction • nmCC + charm + hadroninteraction • nmNC + 2 hadroninteractions • nm CC + 2 hadroninteractions Preliminary A complete simulationwasperformed, considering the observedtopology and OPERA event location efficiencies, 0.1 eventsexpected.

9. Event classification by multivariate analysis Preliminary Event114301850 The event is classified as a tau neutrino interaction with charm production, never observed before !! The significance evaluated with respect to the background only hypothesis is 3.5 s

10. Multiplicitystudies in neutrino-leadscattering • The average charged particles multiplicity at primary vertex was measured. • Test for phenomenological and theoretical models • Provides data to tune MC event generators. • Test KNO Scaling submitted to EPJC and arXiv(http://arxiv.org/abs/1706.07930)

11. m.i.p. The average charged particles multiplicity at primary vertex was measured also for different Ionization (Ngrains/100 mm), this is peculiar in emulsion. Graytracks Nuclearfragments

12. Cosmic-muons rate temperature dependance Atmospheric temperature increaseaffects the cosmic-muons rate Preliminary

13. Thanks for the attention 28 institutions - 140 physicists http://operaweb.lngs.infn.it Part of the OPERA Collaboration Bari BolognaLNF FrascatiLNGS Napoli PadovaRoma Salerno IHE Brussels Hamburg IRB Zagreb LAPP Annecy IPHC Strasbourg METU Ankara AichiToho KobeNagoya NIhon INR Moscow LPI MoscowSINP MSU Moscow JINR Dubna LHEP Bern Technion Haifa Jinjiu