OPERA Status Report

D. Autiero, IPN Lyon (on behalf of the OPERA Collaboration)

IntroductionRunning in 2008-2010Analysis resultsA first tau candidate

97th Meeting of the SPSC29/6/2010

2010: OPERA started its 3rd “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, 2nd 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) Year Beam days

Protons on target

Events in the bricks

2008

123 1.78x1019 1698

2009

155 3.52x1019 3693

2010

187 1.33x1019 (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 (4.5x1019 pot) Aim at high-intensity runs in 2011 and 2012 …

2010

2009

2008 Days

2010: 3rd 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 4.25x1019 pot

Some details of 2010 CNGS run

201020092008

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 backgroundMuon identificationNC/CCMuon momentum/charge measurementHadronic showers measurementCosmic 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 yearExtraction of few tens blocked bricks

BMS

Films developmentfacility

6 automatic lines: max 150 bricks/weekUnderground CS development: max 300 CS/week

Double BMS shift

Scanning

Nagoya

LNGSCS scanning:2 facilities ~ 200 cm2 emulsion film surface/hour/facility

Bricks scanning: 12 Labs

Concurrent activities:

CS scanning for bricks tagging (new strategy with 2009 run)Vertex locationDecay Search (D.S.), since Dec. 2009Scan-forth (Bck. measurements, min. bias kinematics) 9m done. Goal100m scanned track length in 1.5 yearsSpecial 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 runOverall location efficiency (Brick finding * CS * Vertex location):NC like events: 47%CC like events: 76%

e candidate eventFrom 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 2008+2009 2010 events scanning going in parallel

Increased event location rate during last month (>200 events/month)

Located vertices: 2013 events (65% of 2008+2009)Decay Search completed: 1402 events (45% of 2008+2009)

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/eventJune 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

Charm candidate event (dimuon)

4 mm

flight length: 1330 micronskink angle: 209 mradIP of daughter: 262 micronsdaughter muon: 2.2 GeV/cdecay Pt: 0.46 GeV/c

kink

x-view

1ryvertex

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 topologyExpected BG: 1.7 events (loose cuts: work in progress to reduce BG)

Reconstruction eff. for each topology

Charm sample

First candidate http://arxiv.org/abs/1006.1623 Physics Letters B (PLB-D-10-00744)

Big momentum given to many analysis activityAnalysis 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 sampleDATA/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 2008-2009 run statistics, corresponding to 1.85 x 1019 pot

With the above statistics, and for m223 = 2.5 x10-3 eV2 and full

mixing, OPERA expects ~ 0.5 events

* Actual DS statistics 1402 events ~45% of 2008-2009 statistics

Muonless event 9234119599, 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 detectedLarge area scanningFull reconstruction of vertices and gammas

From CS to vertex location

Event reconstruction

Event tracks’ features TRACK

NUMBERPID Probability MEASUREMENT 1 MEASUREMENT 2

tan ΘX tan ΘY P (GeV/c) tan ΘX tan ΘY P (GeV/c)

1

HADRONrange in

Pb/emul=4.1/1.2 cm

Prob(μ)≈10-3 0.177 0.3680.77

[0.66,0.93]0.175 0.357

0.80 [0.65,1.05]

2 PROTONrange,

scattering and dE/dx

-0.646 -0.0010.60

[0.55,0.65]-0.653 0.001

3 HADRONinteraction

seen0.105 0.113

2.16 [1.80,2.69]

0.110 0.1131.71

[1.42,2.15]

4 (PARENT) -0.023 0.026   -0.030 0.018  

5

HADRON:range in

Pb/emul=9.5/2.8 cm

Prob(μ)≈10-3 0.165 0.2751.33

[1.13,1.61]0.149 0.259

1.23 [0.98,1.64]

6

HADRON:range in

Pb/emul=1.6/0.5 cm

Prob(μ)≈10-3 0.334 -0.5840.36

[0.27,0.54]

7From a prompt neutral particle

0.430 0.4190.34

[0.22,0.69]0.445 0.419

0.58 [0.39,1.16]

8(DAUGHTER)

HADRONinteraction

seen -0.004 -0.008  12 [9,18] -0.009 -0.020

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

8

35

8

5 3

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 X0

• gamma search performed in the whole scanned volume• careful visual scanning checksDistance from

2ry vertex (mm)Energy (GeV)

1st 2.2 5.6 ± 1.0 ± 1.7

2nd 12.6 1.2 ± 0.4 ± 0.4

2

1

8 daughter

Distance from 2ry vertex (mm)

IP to 1ry vertex (m)<resolution>

IP to 2ry vertex (m)<resolution>

Prob. of attach. to 1ry vtx*

Prob. of attach. to 2ry vtx*

Attachment hypothesis

1st 2.2 45.0 <11> 7.5 <7> <10-3 0.32 2ry vertex

2nd 12.6 85.6 <56> 22 <50> 0.10 0.82 2ry vertex (favored)

attachment to the vertices

1ry vertex2ry 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 VARIABLE AVERAGE

kink (mrad) 41 ± 2

decay length (m) 1335 ± 35

P daughter (GeV/c) 12 +6-3

Pt decay (MeV/c) 470 +230-120

missing Pt (MeV/c) 570 +320-170

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 2ry vertex

Azimuthal angle between the resulting hadron momentum direction and the parent track direction

Signal :=180o

-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 (0.5-15 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 angulardeflection

Pt of secondary pion

mrad GeV/ctails of the distributions

x 10-4

+

Momentum GeV/c

-

K+ K-

p

Momentum GeV/c

Momentum GeV/c Momentum GeV/c

Momentum GeV/c

x 10-4

x 10-4x 10-4

x 10-4

Kink probabilities for 1 mm Pb

kink probabilities integrated over NC hadronic spectrum yield a BG probability of:

(1.9 ± 0.1) x 10-4 kinks/NC (2 mm Pb)

• no events in the signal region

• 90% CL upper limit of 1.54 x 10-3 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

Kinks Kinks

Background expectations 1-prong hadron decay channel:(~ 50% syst. error for each component)

0.011 events (reinteractions)0.007 events (charm, assuming standard mu ID)

---------------------------------0.018 ± 0.007 (syst.) events 1-prong hadron

BCK for all decay modes: 1-prong hadron, 3-prongs + 1-prong μ + 1-prong e :0.045 ± 0.020 (syst.) events total BG

Assuming m223 = 2.5 x 10-3 eV2 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% CLm2

23 values > 7.5 x 10-3 eV2 (full mixing)

Background fluctuation probabilities to 1 event:

1-prong hadron channel only: P=1.8% 2.36 significanceAll decay modes included in search: P=4.5% 2.01 significance

Since 2008 improving CNGS performance, aiming at nominal one (4.5 1019 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 2008+2009 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 m2 = 2.5 x 10-3 eV2

Background

17.7 2.9 0.17

e 17.8 3.5 0.17

h 49.5 3.1 0.24

3h 15.0 0.9 0.17

All BR*eff

=10.6%10.4 0.75

5 years of nominal beam 4.5 E19 pot/year:

OP

ER

A

Dis

cove

ry p

rob

ab

ility

(%

)

m2 (eV2)

4- evidence

3- evidence

MINOS 2008

Background components:

Production of charmed particles in CC interactions(all decay channels)

Primary lepton unidentified

-,e-,e

D+

+

e+

h+

-

Coulombian large angle scattering of muons in leadBck. to

Hadronic interactions in lead: Bck. to h

or to (if hadron misid. as muon)

h

The number of signal events goes as (m2)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

35

20 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

3 2

7

51

6

8 daughter

4

1

1mm lead

PL19 PL20 PL21PL17 PL18

kink point

6

2

84

3

5

1 7

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 ~ 10-7/CC• Decay of charmed particles produced in e interactions ~ 10-6/CC • Double charm production ~ 10-6/CC

•Hadronic reinteractions (UPDATE) ~ 10-5/CC

•Decay of charmed particles produced in interactions ~ 10-5/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

12 +6-3 GeV

41 ± 2 mrad

Kinematical cuts to be passed

Reject NC events withlarger 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

44

570 +320-170 MeV

470 +230

-120 MeV

o mass mass

120 ± 20 ± 35 MeV 640 +125-80

+100-90 MeV

Event natureThe 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 thedecays: .

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+D+

primary lepton not identified

Charm background