OPERA experiment T.Toshito (Nagoya univ. Japan) for the OPERA collaboration Apr

CNGS beam Due to CERN financial situation we have one year delay. The beam will start on spring L=732km =17GeV 400GeV protons from SPS ν μ beam Optimized to study ν τ Δm 2 =3×10 -3 eV 2 (SK atm. ν) Construction started on Oct. 2000

Detector Hall C Pb Emulsion layers  1 mm ECC(Emulsion Cloud Chamber) to detect decay topology of τ μspectrometer ECC bricks+scintillator strips ν Gran Sasso 1.8kton proven by DONUT

10 cm Brick assignment Plastic scintillator strips (2.6cm width) (x,y) Pulse height 8cm 58emulsion+57Pb plates 10X cm 8cm 10cm 8kg 235k bricks

Emulsion read-out (Super-Ultra Track Selector) S-UTS Scanning speed: 20cm 2 /h ×20 faster than current system (UTS) Fast CCD camera (3k frames/sec) Continuous movement of the X-Y stage Z movement controlled by piezo actuator developed at Nagoya Univ.

~30 Events./day = 30 Bricks Extraction of the Tagged Brick (every day) emulsion development Cosmic ray exposure (for alignment) emulsion read-out Quasi on-line ECC analysis Brick disassembling scanning Nagoya Univ.

“ Long decays  reconstruct kink topology “ Short decays  detect large impact parameter track Decay search I.P.>5~20μm τ→ e 0.9 τ→μ 0.5 τ→ e 3.1 τ→μ 2.9 τ→ h 3.4 ΔΘkink > 20mrad expected 2.4×10 -3 eV 2 & full mixing

Electron identification e π Test CERN (May2001) Data MC 2GeV 4GeV eff~90%, mis-id prob~5% Shower detection & χ 2 analysis

Electromagnetic shower MC Data Test CERN a few GeV Energy determination by calorimetric method

Sensitivity 5 years 3 years exclusion plot in the absence of a signal 1.8kton 1.2×10 -3 eV 2 expected signal 2.4×10 -3 eV 2 30k ν μ CC+NC ~120ν τ CC

Summary OPERA ν τ appearance experiment at CNGS sensitive to SK atm. ν region S-UTS: start test operation in this year Electron ID and shower analysis in ECC: required performance is achieved Ready for data taking in 2006 one year delay due to CERN financial situation