Diapositiva 1

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, Como26/09/20132Fabio Pupilli - XIV ICATPPOutline The OPERA experiment Physics goal Detector description Detector operation Status of data analysis

oscillation search status

e oscillation search status

Opera Collaboration140 physicists, 28 institutions from 11 countriesNihonOSCILLATION PROJECT WITH EMULSION TRACKING APPARATUS326/09/2013Fabio Pupilli - XIV ICATPPGoal: first direct observation of appearance from oscillation at atmospheric scale Long Baseline (730 km) experiment in the CNGS (CERN Neutrino to Gran Sasso) beam Located in LNGS 1400 m rock overburden, low cosmic flux (1/m2/h)< E>17 GeVL730 km( e + e) / 0.87 % * / 2.1 % * promptNegligible

Conventional high energy beam optimised for CC interactions observationFull coverage of the parameter space indicated by Super-K, K2K, MINOSLow e contaminationConstraints on e oscillations*Interaction rate at LNGS3The nt Detection principle

26/09/20134Fabio Pupilli - XIV ICATPPnnm -Decay kinkntnt-gctnm oscillation-, h-, 3h-, e-ct ~ 87 mmEvent by event topological and kinematical reconstructionThe challenge is to distinguish interactions from interactions, through the detection of leptons produced in -CC interactionslead nuclear emulsion target segmented into basic units called bricks Target mass O(kton) (low interaction cross-section) High granularity detector ( decay detection, background rejection)426/09/20135Fabio Pupilli - XIV ICATPP

The OPERA detector*

*JINST 4 (2009) P04018SM1SM2Target area~ 150000 ECC bricks 1.25 kton

ECC (Emulsion Cloud Chamber) brick:56 lead plates (1mm) +57 emulsion films (300 m) Muon SpectrometerDipole Magnet + RPC + Drift Tubes

Each brick followed by 2 removable emulsion films (CS) and planes of plastic scintillator strips in X/Y direction (TT)526/09/20136Fabio Pupilli - XIV ICATPPEVENT RECONSTRUCTION: ELECTRONIC DETECTORS*

Develop this brick

20 m

Selection of contained and on-time events

Muon reconstruction and classification as CC-like (1) or NC-like (0)

Muon momentum and charge measurement through the spectrometerWith : CC CC, (17.7%)Without : NC CC, e(17.8%) CC, h,3h (64.5%)eCC Identification of interaction brick, using TT data in interplay with CS analysis* [New J.Phys. 13 (2011) 053051]26/09/20137Fabio Pupilli - XIV ICATPPEvent Reconstruction: ECC Brick

nm_125756555453525150494821CSd CS analysis: interface between electronic detectors (pos ~ 8 mm, ~ 15 mrad) and emulsion

CS to brick connection (pos ~ 70 m, ~ 8 mrad) and scan back: stopping point definition

Volume scan: topological vertex reconstruction and decay search26/09/20138Fabio Pupilli - XIV ICATPPEvent Reconstruction: Decay Search and Kinematical reconstructionDecay 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 nm events (Data)Momentum measurementComparison with electronic detector (ED) measurement

Event kinematics reconstructed using:

momentum measurement by Multiple Coulomb Scattering in lead [New J.Phys. 14 (2012) 013026]

e.m. shower energy measurement using calorimetric techniques

26/09/20139Fabio Pupilli - XIV ICATPPStatus of Data AnalysisYearp.o.t.In-target eventsIntegrated p.o.t / proposal value*20081.7 x 101916987.7%20093.52 x 1019355723.4%20104.04 x 1019391241.6%20114.84 x 1019421062.7%20123.86 x 1019368079.9%*Proposal value: 22.5 x 1019 p.o.t.

Target mass evolution-9.3%Target loss: ~ 112 tonsLocated neutrino interactions6299Fully analysed events5497 candidate events3Analysis still on going26/09/201310Fabio Pupilli - XIV ICATPP CONTROL SAMPLE: CHARM EVENTS

Charm lifetime and decay topologies analogous to tau: benchmark for decay finding efficiency2008 2010 data sample

Expected events: 53 5Observed events: 50

Kolmogorov test 0.9926/09/201311Fabio Pupilli - XIV ICATPP The first candidate

Decay vertex: 0 - 0

Found in 2008-2009 decay searched data, released in 2010[ Phys. Lett. B 691 (2010) 138 ]All primary tracks incompatible with muon hypothesis26/09/201312Fabio Pupilli - XIV ICATPP

The second candidate

Primary track incompatible with muon hypothesis All tracks identified as hadrons

Event satisfies criteria for: h+h-h-[ arXiv:1308.2553 ](submitted to JHEP)26/09/201313Fabio Pupilli - XIV ICATPP The third candidate

Negative charge of the secondary muon assessed with 5.6 significance (by spectrometer measurement)Cuts for channel passedDecay in plastic base

Primary track incompatible with muon hypothesis26/09/201314Fabio Pupilli - XIV ICATPP oscillation search statusExpected Signal(m23 2 = 2.32 x 10-3 eV2)Expected Background h0.310.027 3h0.430.116 0.33 *0.021 * e0.460.020Total1.530.184With a simple counting method 3.1 significance of non-null observation3 observed events in the h , 3h , channels

Combining different channels, taking into account different signal to noise ratios:

3.4 significance of non-null observation

*1 2011+2012 statistics not includedPreliminary*conservative number, assuming the whole 1 2011+2012 statistics26/09/201315Fabio Pupilli - XIV ICATPP e oscillation search status*

E = 15.6 GeV

2008 2009 data sample

19 e candidates observed19.82.8 (syst.) events expected from bkgThree flavour mixing analysis (Ecut = 20 GeV):

4 observed events4.6 expected

Non standard oscillations at large m2 (Ecut = 30 GeV):

6 observed events9.4 expected

sin2(213) < 0.44 (90% C.L.) sin2(2new) < 7.2 x 10-3 (90% C.L.)* [ JHEP 1307 (2013) 004 ]26/09/201316Fabio Pupilli - XIV ICATPPConclusions OPERA successfully ran on the CNGS neutrino beam from 2008 to 2012. Analysis is still on going.

17.97 x 1019 p.o.t. were collected (about 80% of the CNGS nominal value)

oscillation results: Evidence for oscillation in appearance mode 3 events observed in the analysed sample 3.4 significance of non-null observation More elaborated statistical analysis, exploiting kinematical characteristics of the events, under development

e oscillation results: Upper limit of 0.44 at 90% C.L. on sin2(213) [three flavour mixing] Upper limit of 7.2 x 10-3 at 90% C.L. on sin2(2new) [non standard oscillations at large m2]