The OPERA long baseline neutrino experiment : status and first results. Magali Besnier Laboratoire d’Annecy-le-Vieux de Physique des Particules On behalf of the OPERA collaboration LLWI 08 - february 21st 2008

OPERA Oscillation Project with Emulsion tRacking Apparatus Search for tau neutrino appearance at Gran Sasso laboratory in a pure muon neutrino beam produced at CERN (732 km) First direct observation of nm nt oscillation Possibility of nm ne oscillation search for q13 measurement International Collaboration (Europe + Asia) IIHE (ULB-VUB), Brussels Sofia IHEP Beijing, Shandong IRB Zagreb LAPP Annecy, IPNL Lyon, IRES Strasbourg Berlin Humboldt, Hagen, Hamburg, Münster, Rostock Technion Haifa Bari, Bologna, LNF Frascati, L’Aquila, LNGS, Napoli, Padova, Roma La Sapienza, Salerno Aichi, Kobe, Nagoya, Toho, Utsunomiya INR Moscow, ITEP Moscow, JINR Dubna, Obninsk Bern, Neuchâtel, Zurich METU Ankara 37 INSTITUTS, ~160 PHYSICISTS

vacuum tests successful CNGS beam (CERN Neutrino to Gran Sasso) vacuum 4.5 1019 p.o.t. /year 700 m 100 m 1000m 67 m To Gran Sasso 400GeV Ø at GS=2km 3.2° angle Decay tube vacuum tests successful target Muon chambers Horn Hadron stop Civil engineering completed (June ’03) Hadron stopper and decay tube installed (June ’04) Target section completed in 2006 (first CNGS beam in August 2006)

t nt CNGS beam (CERN Neutrino to Gran Sasso) P(nm->nt)*s(nt CC) Dm223 = 2.5 10-3 eV² nm Flux at Gran Sasso (given by Fluka) nm flux CNGS beam (CERN Neutrino to Gran Sasso) 4.5 1019 p.o.t. /year Number of expected events at Gran Sasso (0-100 GeV): (before reconstruction and detection efficiencies) N nm CC= 3000/yr/kton N ne CC= 20 /yr/kton N nt CC= 14 /yr/kton .Detection of  CC interaction and direct observation of decay topology .High background rejection t-  m- nt nm (17.4%) t-  e- nt ne (17.8%) t-  h- nt n(po) (49.5%) t-  p+ p- p- nt n(po) (14.5%) nt t t decay kink ~ 0.6 mm  appearance signature

OPERA Performances for nm  nt oscillation full mixing, 5 years run @ 4.5x1019 pot / year channel Reconstruction efficiency % Back-ground 11.06 10.4 14.9 0.75 Total Number of expected signal and background events 4-s evidence 3-s evidence OPERA Discovery probability vs. Dm2 Most important background : charm particle production Discovery probability (%) Best value of Dm223 = 2.5 10-3 eV² 3s range : 1.9 - 3.2 10-3 eV² T.Schwetz, hep-ph/0606060 4s Discovery probablility > 90% for Dm223>2.5 10-3 eV² 0 20 40 60 80 100 3s range 0 .05 0.1 0.15 0.2 0.25 0.3 0.35

1.35 kton lead target ~4000 nmCC/yr OPERA detector at LNGS (Notional Laboratory of Gran Sasso, Italy, 120 kms from Rome) rock thickness 1400m (3800 m.w.e.) cosmic muon flux: 1/m2/h m spectrometer: Dipolar magnet + RPC chambers Target Trackers Pb/Em. target Precision tracker: Drift tubes n B=1.6 T 2 super modules 1 super module = 29 walls + 31 Target Tracker + 1 muon spectrometer (22 RPC planes + 6 drift tube planes) 154 750 bricks 1.35 kton lead target ~4000 nmCC/yr 52*51 bricks/wall p/p < 20% for E<50GeV OPERA (CNGS1) ICARUS (CNGS2) Hall C Hall B BOREXINO brick (56 Pb/Em. “cells”) 8 cm (10X0) scintillator strips brick wall module LNGS-INFN

OPERA bricks : main target detector component Emulsion Cloud Chamber (ECC) : 1 ECC brick = 56 sheets Pb + 57 photographic emulsions Pb Emulsion layers n t 1 mm 300µm emulsion films and 1mm thin lead foils by Fuji Film (Japan) JLGoslar (Germany) This technology allows a few micron spatial resolution, and a 3D reconstruction of particle tracks, necessary for t detection 12.5 cm 8 cm 8.6 kg 10 cm 12.5cm 10.2cm 2 emulsion layers (45 m thick) poured on a 210 m plastic base The most precise tracker Résolution (microtracks) spatial : 0.06 µm Angular : ~ 2 mrad Vertex position resolution : ~1µm in transverse plane 2mm 6mm MC ntt3h - Measurement of hadrons momenta by MCS - dE/dx pion/muon separation at low energy - Electron identification and energy measurements for electrons and photons Reconstructed electronic shower 14 mm

BAM (Brick Assembling Machine) Target preparation BAM (Brick Assembling Machine) Automatic lead/emulsion piling in a dark room (~700 bricks/day) 5 articulated robots 2003 : start building detector June 2008 : end of filling target Begining 2007 now Insertion and extraction of bricks following intelligent procedures. The BMS(Brick Manipulator System) one robot on each side of the detector now

LNGS Hall C Detector today : electronics fully instrumented and tested Brick filling on the way : 99000 Bricks already inserted LNGS Hall C

OPERA event analysis procedure 0 max p.h.  Brick finding : 31 tracking scintillator planes (TT)/super modules Trigger(>99%) + Brick finding (7090%) selection of the interaction brick provided by time correlation of electronic detectors Emulsion Development of candidate bricks at Gran Sasso (surface facilities) 20-30 bricks extracted / day Emulsion shipment Example of a vertex in emulsion Emulsion Scanning with automated microscopes : 10 laboratories in Europe and Japan

emulsion digitisation Scanning : emulsion digitisation Reconstruction of micro-tracks (45µm) 10 scanning laboratories in Europe and Japan 16 tomographic images = 45µm 300µm Field of vue 2D images processing 3D reconstruction of particle tracks 2 emulsion sides (45 mm) 1 plastic base (200 mm) speed : 20cm²/hour/emulsion side Résolution (grains) spatial : 0.06 µm Angular : ~ 2 mrad 1 emulsion sheet (2 sides) : 12h scanning - ~5GB

n interaction in magnet (Fe) First OPERA results with CERN neutrino beam Positive electronic tests during first beam run (August 06 : 0.084 1019 integrated pot) n interaction in magnet (Fe) cosmics Beam events More than 300 registred events correlated in time with beam : interactions inside the rock and inside the detector (TT and spectrometers) First events from the CNGS neutrino beam detected in the OPERA experiment R. Acquafredda et al 2006 New J. Phys. 8 303

Muon track inside emulsions First OPERA results with target bricks from cosmic run < 1 event per day inside the acceptance ! ~20 ‘good’ muons per month Muon track inside emulsions April 17th- May 15th 2007 : 30 bricks extracted 28 muons found in emulsions 45 µm Cosmic muons in OPERA detector (ray bandle) 210 µm Mean prediction accuracy (ED-brick): Δx = 11 mm (along the tray) Δy = 14 mm (vertical direction) Δθx = 6.0 mrad Δθy = 3.3 mrad These first data have confirmed the good accuracy of the ED predictions and validated the analysis chain

Problems in ventilation control units of the proton target First OPERA results with target bricks from CNGS run (SM1 filled at 80%) Nominal intensity : 4.5 1019 pot /yr (1yr=200 days) CNGS integrated intensity from September 24th to October 20th : 8.24 1017 pot 20/10/07 12/10/07 Comissioning Physics Problems in ventilation control units of the proton target 9/10/07 6.72 1017 pot 59 : CNGS very stable at 1.58 1017 pot/day 326 expected events in bricks 38 events registered during the 2007 CNGS run : 29 CC 9 NC Expected 75% CC and 25%NC proportions 5/10/07 3.91 1017 pot

nµCC 18 m m- nµ Em=7.8 GeV n 12/29 located in bricks so far 1 cm First OPERA neutrino event located in brick (October 2nd 2007) nµCC Hadronic shower muon nµ m- Hadronic shower Em=7.8 GeV n 12/29 located in bricks so far 18 m Bologna scanning laboratory 1 cm

3/9 located in bricks so far nµ NC Hadronic shower nµ n Hadronic shower 3/9 located in bricks so far 18 m Nagoya scanning laboratory 2 cm

Conclusion OPERA is the first experiment for nt appearance in a nm beam Hybrid detector with passive lead target and active electronic detectors Electronic parts fully commissioned 0.9 kton (99000 Bricks) already inserted in the detector First results CNGS beam run in August 2006 : electronic detectors gave good results Cosmic run : brick candidate extraction ; scanning and analysis have validated the full analysis chain Neutrino events have been observed in OPERA bricks during the CNGS beam run of 2007. Location and reconstruction of neutrino vertex in emulsions was an important learning phase. Analysis is on the way. Future Next CNGS beam run with full target completed expected by june 2008 ~20 neutrino interactions / day  1st t event expected

CNGS beam @ CERN: Proton extractions from SPS with 3 cycles of 6s each : 2 extractions of 10.5 ms, separated by 50 ms. time ~1extraction Beam event selection : TOPERA – (TSPS + TOF) < Tgate ~2.4ms Nominal intensity : 4.5 1019 pot /yr, with 2.4 1013 pot/extraction (FE)

Control of the neutrino beam direction: With the horizontal profile of the CNGS muons in the 2 muon detectors 1st muon chamber 2nd muon chamber p m, nm >1km 67m - First muon detector : ≤ 2.5 x 107 muons / cm2 / 1013 pot - Second muon detector :  ≤ 4 x 105 muons / cm2 / 1013 pot

CERN-LNGS time correlation All events within a window of +- 20 ms since the beginning of the extraction Extraction 1 Should start at 0 and last up to 10500 µs.  New calibrations will be done with a new GPS system receiver and a Cs clock of 1ns accuracy. ns Extraction 2 ns

Target chamber Solution : Replace damaged electronics Find another place for ventilation control units These doses were computed by the Fluka group and known since many years !! They were not just taken into account when the ventilation was installed Radiation protection measurements confirm the calculations

1.7 m 6.9m Target Tracker Reconstructed cosmic track LNGS 64 strips/module ●Trigger:  > 99% ● Brick finding :   7080% ● Initiate muon tagging Plastic scintillator strips (AMCRYS-H, 6.7m x 2.6cm x 1cm) readout by Kuraray WLS fibres + Hamamatsu PMT’s (64 channels) Tracker wall 2 x 256 strips Reconstructed cosmic track LNGS

Muon spectrometer Inner Tracker: 11 planes of RPC’s B= 1.55 T base slabs coil 8.2 m M ~ 950t Drift tubes 12 Fe slabs (5cm thick) RPC’s 2 cm gaps Inner Tracker: 11 planes of RPC’s 21 bakelite RPC’s (2.9x1.1m2) / plane Precision tracker: 6 planes of drift tubes diameter 38mm, length 8m 4 staggered layers / plane, each layer consisting of 168 tubes efficiency: 99% space resolution: 300µm  identification:  > 95% (TT) p/p < 20% , p < 50 GeV/c misidentified  charge prob.  0.1  0.3%

PEANUT : OPERA test-beam at FERMILAB goal : to observe neutrino interactions in OPERA bricks Detector placed in the front of the MINOS near detector: -4 walls of 3*4 OPERA bricks exposed to NUMI beam (nm ) in « low energy » configuration (<E>=10GeV, Epeak=3GeV ) -DONUT SFT (scintillators) between each wall Brick piling in dark room 5 nm events/brick /day expected bricks exposed ~20days Exposure time: October 18th 2005 -> Mars 1st 2006 total 160 Bricks made, exposed and developped developper SFT-emulsions alignment Neutrino reconstruction in emulsions ~500µm spatial resolution ~5mrad angular resolution Salerno scanning lab analysis

  e oscillation search 2.5x10-3 eV2 m232 = 2.5 x 10-3 eV2 23 = 45° nominal CNGS beam 5 years Combined fit of Ee, Evis, (pt)miss sin2(213)<0.06 13 < 7.1º 90% C.L. limits on sin2(213) and 13 :