OPERA Status Report D. Autiero, IPN Lyon (on behalf of the OPERA Collaboration) Introduction Running in Analysis results A first tau candidate 97 th Meeting of the SPSC 29/6/2010

2010: OPERA started its 3 rd “Physics run” First two years characterized by interplay of learning and approaching more and more a routinely operation: CNGS: improving performance with time  converging to nominal figure Detector operation: DAQ for cosmics all year  increasingly smooth and automatic operation Bricks handling: removal of black CS in 2009  regular, reliable extraction/handling operations Scanning: Location procedures at CS and brick level  new CS strategy since 2009, additional tasks added for analysis needs Decay search: procedure launched at the end of 2009, 2 nd version now Analysis: data exploitation for validation of Bck. and efficiencies, charm sample. Last months activity first  candidate  many aspects useful for learning Introduction

OPERA running (CNGS) YearBeam days Protons on target Events in the bricks x x x10 19 (28 June) 1430 (28 June) 6821 events collected until 28 June 2010 (within 1  in agreement with expectations) SPS efficiency: 61-73% High specific CNGS efficiency: 97% 2010: hoping to get as close as possible to nominal year (4.5x10 19 pot) Aim at high-intensity runs in 2011 and 2012 … Days 2010: 3 rd physics run since 2008 pot

 2010 run started with MTE and then switched back to CT  Lower average intensities than 2009 at present  Rough extrapolation of 2009 performance to number of days in 2010 would yield 4.25x10 19 pot Some details of 2010 CNGS run

Cosmics CNGS events Electronic Detectors data taking Continuous operation and cosmics data taking during all the year ~100% live time (apart few hours of power cuts and small accidents) Electronic Detectors analysis (paper in preparation): Events selection and external events background Muon identification NC/CC Muon momentum/charge measurement Hadronic showers measurement Cosmic ray studies Dedicated min. bias trigger (4 hits) during CNGS spills since 2010

Brick Handling activities (all the year) BMS extraction: 25 bricks/8 hour shift ~90’000 bricks handled until 2009 to extract ~7000 event bricks Operation time ~80% of the year Extraction of few tens blocked bricks BMS Films development facility 6 automatic lines: max 150 bricks/week Underground CS development: max 300 CS/week Double BMS shift

Scanning Nagoya LNGS CS scanning: 2 facilities  ~ 200 cm 2 emulsion film surface/hour/facility Bricks scanning: 12 Labs Concurrent activities: CS scanning for bricks tagging (new strategy with 2009 run) Vertex location Decay Search (D.S.), since Dec Scan-forth (Bck. measurements, min. bias kinematics) 9m done. Goal  100m scanned track length in 1.5 years Special measurements on decay candidates: large volumes, showers, kinematics, tracks follow-down, re-measurements

CS tagging strategy 2008:  matching or 1 hadronic track matching to ED (≥3 hits in both projections on 2cm road) 77% efficiency with two Most Prob. CS (83% up to 4 M.P. CS) 88% purity CS tagging strategy since 2009: Harder cuts on hadronic tracks (>=2 tracks): 72% efficiency (2 M.P. CS) 96% purity Slightly better  *purity Lower scanning effort  Ongoing Data/MC comparisons to improve the location efficiency for NC like events  Electron searches in 691 events which underwent the DS procedure, 6 e CC candidates Location results of 2008 run Overall location efficiency (Brick finding * CS * Vertex location): NC like events: 47% CC like events: 76%

e candidate event From a subsample equivalent to ~ 800  cc located events we detected 6 e candidates

 CS and brick scanning of 2008 data completed  First CS scanning for 2009 completed, lower prob. CS continuing  by end 2010: DS completed for  2010 events scanning going in parallel Increased event location rate during last month (>200 events/month) Located vertices: 2013 events (65% of ) Decay Search completed: 1402 events (45% of )

Scanning activities (till fall 2009) focused on event/vertex location Decay search  Systematic DECAY SEARCH started in December 2009 on 2008 and 2009 data to detect all possible decay topologies (charm +  ) 1) improvement of the vertex definition and IP distribution 2) detection of possible kink topologies (on tracks attached to primary vertex) 3) search for extra tracks from decays not attached to primary vertex  Rescanning of 2008 volumes: extended from 6  10 plates downstream vertex  Loose cuts for background studies  Full MC implementation of DS for comparison to charm sample  DS scanning time up to few hours/event June 2010: set-up revised version with harder cuts (≤ 1 hour/event)

Impact parameter measurement (a trigger used in the DS procedure) IP distribution for   events (MC) IP distribution for:   events (MC) NC+CC  events (MC), NC+CC  events (Data) expanded scale mm

Charm candidate event (dimuon) 4 mm flight length: 1330 microns kink angle: 209 mrad IP of daughter: 262 microns daughter muon: 2.2 GeV/c decay Pt: 0.46 GeV/c kin k x-view 1ry vertex 1.3 mm 1ry muon daughter muon

P daughter >2.5 GeV/c, kink Pt > 0.5 GeV/c (for kink events) looser cuts for multi-prong events DS procedure fully simulated Examples of distributions: 18 charm candidate events selected by the kinematical cuts, 3 of them with 1-prong kink topology. Expected: 15.5 ± 2.8 out of which 0.79 ± 0.22 with kink topology Expected BG: 1.7 events (loose cuts: work in progress to reduce BG) Reconstruction eff. for each topology Charm sample

First  candidate Physics Letters B (PLB-D ) Big momentum given to many analysis activity Analysis not made ad hoc for this candidate but by using the Proposal cuts Complete revision of simulation and commissioning of a variety of techniques: Understanding of hadronic reinteractions MC of general use for , charm … Direct BCK measurement from scan-forth sample DATA/MC scan-forth sample, test-beam brick First full scale demonstration of tracks-follow down to complement  -id  promising handle for background reduction Study of kinematics, MCS measurements, particles ID … Electromagnetic showers energy reconstruction …  pointing accuracy,  0 reconstruction Searches for nuclear fragments in hadronic interactions DS validation, charm

Event statistics (corresponding to the publication of the  candidate) Brick tagging efficiency times vertex location efficiency:~ 60% Total found neutrino vertices: 1617 Events for which “decay search” was completed: 1088 (187 NC) This is ~35% of the total run statistics, corresponding to 1.85 x pot With the above statistics, and for  m 2 23 = 2.5 x10 -3 eV 2 and full mixing, OPERA expects ~ 0.5  events * Actual DS statistics 1402 events ~45% of statistics

Muonless event , taken on 22 August 2009, 19:27 (UTC) (as seen by the electronic detectors)

CS predictions Scan-back in ECC CS predictions a kink is detected Large area scanning Full reconstruction of vertices and gammas From CS to vertex location

Event reconstruction

Event tracks’ features TRACK NUMBER PIDProbability MEASUREMENT 1MEASUREMENT 2 tan Θ X tan Θ Y P (GeV/c)tan Θ X tan Θ Y P (GeV/c) 1 HADRON range in Pb/emul=4.1/1.2 cm Prob(μ)≈ [0.66,0.93] [0.65,1.05] 2PROTON range, scattering and dE/dx [0.55,0.65] HADRON interaction seen [1.80,2.69] [1.42,2.15] 4 (PARENT) HADRON: range in Pb/emul=9.5/2.8 cm Prob(μ)≈ [1.13,1.61] [0.98,1.64] 6 HADRON: range in Pb/emul=1.6/0.5 cm Prob(μ)≈ [0.27,0.54] 7 From a prompt neutral particle [0.22,0.69] [0.39,1.16] 8 ( DAUGHTER ) HADRON interaction seen [9,18] muonless event (favored hypothesis)

Vertex tracks followed down (through several bricks) to assess the muonless nature of the event. Residual probability of  CC event (due to a possibly undetected large angle muon) ~ 1%. “Nominal” value of 5% assumed

OPERA nominal analysis flow applied to the  ->1 h kink candidates: (more refined selection criteria being developed were not considered here not to bias our analysis) kink occurring within 2 lead plates downstream of the primary vertex kink angle larger than 20 mrad Secondary vertex daughter momentum higher than 2 GeV/c decay Pt higher than 600 MeV/c, 300 MeV/c if ≥ 1 gamma pointing to the decay vertex missing Pt at primary vertex lower than 1 GeV/c Primary vertex azimuthal angle between the resulting hadron momentum direction and the parent track direction larger than  /2 rad Analysis

 detection total radiation length downstream the vertices: 6.5 X 0 gamma search performed in the whole scanned volume careful visual scanning checks Distance from 2ry vertex (mm) Energy (GeV) 1 st  ± 1.0 ± nd  ± 0.4 ± 0.4 22 11 8 daughter

Distance from 2ry vertex (mm) IP to 1ry vertex (  m) IP to 2ry vertex (  m) Prob. of attach. to 1ry vtx* Prob. of attach. to 2ry vtx* Attachment hypothesis 1 st  < ry vertex 2 nd  ry vertex (favored)  attachment to the vertices 1ry vertex 2ry vertex   Pointing resolution (1  ) for a given gamma: function of scattering and distance * probability to find an IP larger than the observed one

Kinematical variables VARIABLEAVERAGE kink (mrad)41 ± 2 decay length (  m) 1335 ± 35 P daughter (GeV/c) Pt decay (MeV/c) missing Pt (MeV/c) ϕ (deg) 173 ± 2 The average values are used in the following kinematical analysis The uncertainty on Pt due to the alternative  attachment is < 50 MeV The kinematical variables are computed by averaging the two sets of track parameter measurements We assume that:  1 and  2 are both attached to 2 ry vertex

Azimuthal angle between the resulting hadron momentum direction and the parent track direction Signal :  =180 o  -decay --    - X (hadron shower)  N  - X --   kink  N   - X --  x BG: small   26 Blue: MC - NC Black: MC -  rad cut

Simulation of the reinteraction BG Background evaluation by using state-of-the-art FLUKA code, upgrade of the Proposal simulations. 160 million events ( GeV/c) of  +,  ,K +,K -,p impinging 1 mm of lead, equivalent to 160 km of hadronic track length. Kink probabilities evaluated by applying the same cuts as for the tau analysis. Typical scattering distributions for : 5 GeV  + 20 mrad 300 MeV/c Pion angular deflection Pt of secondary pion mrad GeV/c tails of the distributions

x ++ Momentum GeV/c -- K+K+ K-K- p x Kink probabilities for 1 mm Pb kink probabilities integrated over  NC hadronic spectrum yield a BG probability of: (1.9 ± 0.1) x kinks/NC (2 mm Pb)

no events in the signal region 90% CL upper limit of 1.54 x kinks/NC event the number of events outside the signal region is confirmed by MC (within the ~30% statistical accuracy of the measurement) signal region 1 cm Measure interaction BG far from the  -decay region = 9 m of hadron track length ~ 8 times scanned track length for NC events (NC x hadron multiplicity x 2 mm). Goal: ~100 m to fully validate (eventually replace) the MC in 1.5 years.

DATA/MC comparison: good agreement in normalization and shape 1-prong multi-prong Data/MC: Brick exposed to 4 GeV/c pions ~20 m of pion track scanned to search for interactions Kinks

Background expectations 1-prong hadron  decay channel: (~ 50% syst. error for each component) events (reinteractions) events (charm, assuming standard mu ID) ± (syst.) events 1-prong hadron BCK for all decay modes: 1-prong hadron, 3-prongs + 1-prong μ + 1-prong e : ± (syst.) events total BG Assuming  m 2 23 = 2.5 x eV 2 and full mixing, we expected: 0.54 ± 0.13 (syst.)  CC events in all  decay channels and 0.16 ± 0.04 (syst.)  CC events in the 1-prong hadron  decay channel This result allows us to exclude at the 90% CL  m 2 23 values > 7.5 x eV 2 (full mixing) Background fluctuation probabilities to 1 event: 1-prong hadron channel only: P=1.8%  2.36  significance All  decay modes included in search: P=4.5%  2.01  significance

Since 2008 improving CNGS performance, aiming at nominal one ( pot) in 2010 and beyond (2011, 2012, …) Smooth detector and ancillary facilities running  reliability and performance improving with time, small margins for improvements Good understanding of electronic detectors analysis Scanning optimizing and coping to parallel processes: CS tagging, vertex location, scan-forth, Decay Search DS launched at the end of 2009, 45% of completed  First charm results. DS optimized version II released A first  candidate event published, important achievement. Many analysis progresses stimulated by the candidate and availability of new data Next steps: complete measurements from data (DS, BCK, kinematics) and MC implementation of what learned from data (efficiencies,  -ID)  Improved analysis strategy. Looking forward and preparing for next candidates  OPERA goal: discovery of oscillations in direct appearance mode  Requires statistically significative evidence. Still implying strong support from CERN, funding agencies and the whole collaboration Conclusions

OPERA sensitivity  decay channel B.R. (%) Signal  m 2 = 2.5 x 10-3 eV 2 Background        e   h   3h All BR*eff =10.6% years of nominal beam 4.5 E 19 pot/year: OPERA Discovery probability (%)‏  m 2 (eV 2 )‏ 4-  evidence 3-  evidence MINOS 2008 Background components: Production of charmed particles in CC interactions (all decay channels) Primary lepton unidentified  -,e - ,e D+D+ +e+h++e+h+  -- Coulombian large angle scattering of muons in lead Bck. to    Hadronic interactions in lead: Bck. to  h or to  (if hadron misid. as muon) h The number of signal events goes as (  m 2 ) 2

Typical  CC- and NC-like events The measured ratio of NC-like/CC-like events after muon ID and event location is ~20%, as expected from simulations m

Momentum measurement by Multiple Coulomb Scattering… Pmcs error bar: 68% CL  p/p  = (22±4)%  test beam …in the lead/emulsion film sandwich and comparison with electronic detector measurements Pmcs-Pspectro Pspectro

 detection and  0 mass reconstruction E = 0.5 GeV E = 8.1 GeV 2 EM showers give a reconstructed mass ~ 160 MeV EM shower energy measured by shower shape analysis and Multiple Scattering method

 0 mass resolution (real data) 35 gamma pairs 1  mass resolution: ~ 45%

Event reconstruction (2) Zoom

Event topological features Side view 2 11 3 2 daughter 4

11 1mm lead PL19PL20PL21PL17PL18 kink point Primary vertex careful visual inspection of the films behind/in front the secondary vertex: no “black” or “evaporation” tracks. Support topological hypothesis of a particle decay

BACKGROUND SOURCES Prompt    ~ /CC Decay of charmed particles produced in e interactions ~ /CC Double charm production ~ /CC Hadronic reinteractions (UPDATE) ~ /CC Decay of charmed particles produced in  interactions ~ /CC

rad Accepted kinks > 20 mrad Kink angle Features of the decay topology red bands: values for the “interesting” event with uncertainties mm Decay length GeV/c cut Daughter momentum 1335 ± 35  m GeV 41 ± 2 mrad

Kinematical cuts to be passed Reject NC events with larger missing Pt (neutrino) Reject hadron interactions Missing Pt at primary vertex cut 44 Pt at decay vertex cut GeV/c Blue: MC NC Black: MC -  GeV/c Missing Pt at primary vertex cut MeV MeV

 o mass  mass 120 ± 20 ± 35 MeV MeV Event nature The event passes all cuts, with the presence of at least 1 gamma pointing to the secondary vertex, and is therefore a candidate to the    1-prong hadron decay mode. Invariant mass reconstruction The invariant mass of the two detected gammas is consistent with the    mass value (see table below). The invariant mass of the    system has a value (see below) compatible with that of the  (770). The  appears in about 25% of the  decays:         .

Charmed particles have similar decay topologies to the  charm production in CC events represents a background source to all tau decay channels this background can be suppressed by identifying the primary lepton  ~ 95% muon ID for the 1-prong hadronic channel 0.007±0.004 (syst) background events are expected for the analyzed statistics further charm BG reduction is under evaluation by implementing the systematic follow-down of low energy tracks in the bricks and the inspection of their end-range, as done for the “interesting” event. For the latter we have 98-99% muon ID efficiency. ,e ,e - +e+h++e+h+ D+D+ primary lepton not identified Charm background