1 / 16

Recent results of the OPERA experiment

Recent results of the OPERA experiment. Fabio Pupilli ( INFN – Laboratori Nazionali del Gran Sasso) on behalf of the OPERA Collaboration 26/09/2013 – XIV ICATPP – Villa Olmo, Como. Outline. Opera Collaboration 140 physicists , 28 institutions from 11 countries.

ellard
Download Presentation

Recent results of the OPERA experiment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent results of the OPERA experiment Fabio Pupilli (INFN – Laboratori Nazionali del Gran Sasso) on behalfof the OPERA Collaboration 26/09/2013 – XIV ICATPP – Villa Olmo, Como

  2. Outline Opera Collaboration 140 physicists, 28 institutionsfrom 11 countries • The OPERA experiment • Physics goal • Detector description • Detector operation • Status of data analysis • νµ  ντoscillationsearch status • νµ  νeoscillationsearch status Nihon Fabio Pupilli - XIV ICATPP

  3. OSCILLATION PROJECT WITH EMULSION TRACKING APPARATUS Goal: first direct observation of ντ appearance from νµ oscillation at atmospheric scale • Long Baseline (730 km) experiment in the CNGS (CERN Neutrino to Gran Sasso) νµ beam • Located in LNGS  1400 m rock overburden, low cosmic µ flux (1/m2/h) Fabio Pupilli - XIV ICATPP Conventionalhighenergybeamoptimisedforντ CC interactionsobservation Full coverage of the parameter space indicated by Super-K, K2K, MINOS Low νecontamination Constraints on νµνe oscillations *Interaction rate at LNGS

  4. - nm n The ntDetection principle The challenge istodistinguishντinteractionsfromνµinteractions, through the detection ofτleptonsproduced in ντ -CC interactions n Decay “kink” -, h-, 3h-, e- nm oscillation t- ct ~ 87 mm nt gct Eventbyeventtopological and kinematicalreconstruction Fabio Pupilli - XIV ICATPP ● Target mass O(kton) (low  interaction cross-section) ● High granularity detector ( decay detection, background rejection) lead – nuclear emulsion target segmented into basic units called bricks

  5. *JINST 4 (2009) P04018 The OPERA detector* SM1 SM2 Fabio Pupilli - XIV ICATPP Target area ~ 150000 ECC bricks  1.25 kton Muon Spectrometer Dipole Magnet + RPC + Drift Tubes Each brick followed by 2 removable emulsion films (CS) and planes of plastic scintillator strips in X/Y direction (TT) ECC (Emulsion Cloud Chamber) brick: 56 lead plates (1mm) + 57 emulsion films (300 µm)

  6. EVENT RECONSTRUCTION: ELECTRONIC DETECTORS* *[New J.Phys. 13 (2011) 053051] • Selectionofcontained and “on-time” events • Muonreconstructionand classificationasCC-like (1µ) or NC-like (0µ) • Muonmomentum and chargemeasurementthrough the spectrometer With µ: ・µ CC ・CC, τ→µ(17.7%) Develop this brick 20 m Without µ: ・µ NC ・CC, τ→e(17.8%) ・CC, τ→h,3h(64.5%) ・eCC Fabio Pupilli - XIV ICATPP • Identificationofinteractionbrick, using TT data in interplay with CS analysis

  7. nm_ Event Reconstruction: ECC Brick CSd • CS analysis: interface between electronic detectors(σpos~ 8 mm, σθ~ 15 mrad) and emulsion • CS tobrick connection (σpos~ 70 µm, σθ~ 8 mrad) and scan back: stoppingpointdefinition • Volume scan: topologicalvertexreconstruction and decaysearch 2 1 1 … 53 57 2 48 49 50 51 52 54 55 56 Fabio Pupilli - XIV ICATPP

  8. Event Reconstruction: Decay Search and Kinematical reconstruction • Decay topologies detected through: • kink angle along tracks attached to the vertex • Impact Parameter (IP) evaluation • IP distribution for: • - nt events (MC) • NC+CC nm events (MC) • NC+CC nmevents (Data) Fabio Pupilli - XIV ICATPP Momentum measurement Comparison with electronic detector (ED) measurement • Eventkinematicsreconstructedusing: • momentummeasurementby Multiple Coulomb Scatteringin lead[New J.Phys. 14 (2012) 013026] • e.m.showerenergymeasurementusingcalorimetrictechniques

  9. Status of Data Analysis *Proposal value: 22.5 x 1019 p.o.t. Fabio Pupilli - XIV ICATPP Target mass evolution -9.3% Target loss: ~ 112 tons Analysis still on going

  10. νµ ντCONTROL SAMPLE: CHARM EVENTS Charm lifetime and decaytopologiesanalogousto tau:  benchmark forτ decayfindingefficiency 2008  2010 data sample Expected events: 53 ± 5 Observed events: 50 Fabio Pupilli - XIV ICATPP Kolmogorov test ≥ 0.99

  11. The firstντ candidate Decay vertex: τ−→ρ− ντ ρ−→π0 π- π0 → γγ Fabio Pupilli - XIV ICATPP All primary tracks incompatible with muon hypothesis Found in 2008-2009 decaysearched data, released in 2010 [ Phys. Lett. B 691 (2010) 138 ]

  12. The secondντ candidate • Primary track incompatible with muon hypothesis • All tracks identified as hadrons • Event satisfies criteria for: • τ h+h-h-ντ [ arXiv:1308.2553 ] (submitted to JHEP) Fabio Pupilli - XIV ICATPP

  13. The thirdντ candidate Decay in plastic base Primary track incompatible with muon hypothesis Fabio Pupilli - XIV ICATPP Negative charge of the secondary muon assessed with 5.6 σ significance (by spectrometer measurement) Cuts for τ µchannel passed

  14. νµ  ντoscillationsearch status Preliminary *1µ 2011+2012 statisticsnotincluded Fabio Pupilli - XIV ICATPP *conservativenumber, assuming the whole 1µ 2011+2012 statistics 3 observedevents in the τ h , τ 3h , τ µ channels Combiningdifferentchannels, takinginto account differentsignaltonoiseratios: 3.4 σsignificanceofnon-nullobservation With a simple counting method  3.1 σ significance of non-null observation

  15. νµ  νeoscillationsearchstatus* * [ JHEP 1307 (2013) 004 ] 2008  2009 data sample 19 νe candidates observed 19.8±2.8 (syst.) events expected from bkg E = 15.6 GeV Fabio Pupilli - XIV ICATPP Three flavour mixing analysis (Ecut = 20 GeV): 4 observed events 4.6 expected Non standard oscillations at large Δm2 (Ecut = 30 GeV): 6 observed events 9.4 expected ⇒ sin2(2θ13) < 0.44 (90% C.L.) ⇒ sin2(2θnew) < 7.2 x 10-3 (90% C.L.)

  16. Conclusions • OPERA successfullyran on the CNGS neutrino beamfrom 2008 to 2012. Analysisisstill on going. • 17.97 x 1019p.o.t.werecollected (about 80% ofthe CNGS nominalvalue) • νµ ντoscillationresults: • Evidenceforνµ ντoscillation in appearance mode • 3 eventsobserved in the analysed sample • 3.4 σsignificanceofnon-nullobservation • More elaboratedstatisticalanalysis, exploitingkinematicalcharacteristicsof the events, under development • νµ νeoscillationresults: • Upper limitof 0.44 at 90% C.L. on sin2(2θ13) [threeflavour mixing] • Upper limitof 7.2 x 10-3 at 90% C.L. on sin2(2θnew) [non standard oscillations at largeΔm2] Fabio Pupilli - XIV ICATPP

More Related