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The Nuclear Emulsion Technology and the Analysis of the OPERA Experiment Data

Learn about the nuclear emulsion technology used in the OPERA experiment to detect neutrino oscillations and analyze the experimental data. Topics include the discovery of charm particles, the detection of neutrino oscillation behavior, and the use of emulsion films and lead plates in the OPERA detector.

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The Nuclear Emulsion Technology and the Analysis of the OPERA Experiment Data

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  1. The Nuclear Emulsion Technology and the Analysis of the OPERA Experiment Data Tsutomu Fukuda Nagoya University, JAPAN On behalf of the OPERA Collaboration DPF-APS 2009 , 28 JULY 2009, Wayne State University in Detroit

  2. Recorded as silver grains along the line particle passed through 50 micron Resolution of 0.3 micron Microscopic Image Nuclear Emulsion • Nuclear Emulsion is a special kind photographic film.: AgBr micro crystal semiconductor (Band gap ~ 2.6eV). • Signal is amplified by chemical process (developing). Nuclear Emulsion is used1947 (C.Powell et al.) Discovery of .1971 (K.Niu et al.)Charm particle is discovered in cosmic-ray (called X-particle).2001 (K.Niwa et al.) The first observation of   at Fermi-Lab. 2009 ?First direct observation of   oscillation appearance Sub micron resolution 3D tracking

  3. OPERA experiment Theory:In 1962, Maki, Nakagawa and Sakata conceived massive neutrino will oscillate.Important experimental result (1):In 1998, Super-Kamiokande detected the behaviour of neutrino oscillation (atmospheric disappearance).Important experimental result (2):In 2001, DONUT ( FermiLab experiment) succeeded in detecting  by Emulsion Cloud Chamber (ECC). Goal: The goal of OPERA is to detect  oscillated fromby ECC.

  4. conventional  beam ( m-2 / pot) 7.45x10-9  CC / pot / kton 5.44x10-17 < E >( GeV ) 17 (e + e) /  0.85 % /  4.0 % prompt negligible   Conceptual Design CERN SPS 730km Appearance ECC detector ~ 1.3kton INFN Gran Sasso Underground Laboratory • The detector is located on the CNGS (CERN Neutrinos to Gran Sasso) beam line at a distance from the neutrino source of 730km. • Δm232 = (2.43±0.13)×10-3 eV2 , sin22θ23 = 1.0 • # of  events = 4300/year • expected detectable # of  CCevents ~2.5/year Here, I will mainly talk about Emulsion Technology and Analysis.

  5. OPERA emulsion film Lead plate : 1mm 75.4mm 125mm 8.3kg 10X0 Neutrino Beam 100mm ECC (Emulsion Cloud Chamber) 57 emulsion films and 56 Pb plates piled up. OPERA film 1mm beam 210μm 44μm emulsion Plastic base Lead

  6. How to detect tau neutrino DONUT event Flight Length：280um   1mm Emulsion DONUT : Iron 1mmOPERA : Lead 1mm

  7. Emulsion Detector (ECC brick) Emulsion + Target Tracker Muon spectrometer TT 2.6cm ECC 10cm 12.5cm Changeable Sheet (CS) Emulsion - Electronic Detectors Hybrid Detector 1.25 kton = 150,000 ECC bricks The OPERA Detector@ Gran Sasso(1400munderground) 

  8.  Flow of Emulsion Analysis Emulsion analysis is performed in two main steps Trigger on Electronic detector ↓Connection from Electronic Detector to Emulsion Detector ↓locating the neutrino interaction in Emulsion Detector 1. Location  2. Decay Search  - - (e-, h-, 3h) Searching for tau decay topology h h

  9. Vertex Location – trigger by electronic detectors – CC-like(with muon)

  10. Vertex Location – trigger by electronic detectors – NC-like(no muon)

  11. extraction The most probable ECC brick is tagged by Target Trackers Vertex Location  ECC CS Only CS Developed →Scanning Check tracks from the interaction . half @ Gran Sasso, half @ Japan

  12. Two films Easily detached Changeable Sheet (CS) Roles of CS Electronic detectors don’t have enough resolution to identify the ECC Brick where the interaction has occurred. To identify the brick, CS is needed. OPERA film produced in Japan. All accumulated background tracks were erased by “Refreshing”@ the underground G.S. lab. In the CS, only ν associated track is recorded.If track is found at CS. the daughter of ν interaction. Emulsion film of ECC are developedIn the case a track is NOT found Next Brick should be taken out. Refresh: keeping the emulsion films at highrelative humidity(98%) and high temperature(30deg C) for 3days. ? Non refresh extraction After refresh Ratio of erasing > 99%

  13. Emulsion Data taking– automatic scanning system – European Scanning System Japanese Scanning System Scanning speed/system: 20cm2/h Customized commercial optics and mechanics asynchronous DAQ software Scanning speed/system: 75cm2/h High speed CCD camera (3 kHz) Piezo-controlled objective lens FPGA Hard-coded algorithms LNGS: 10 systems, Napoli: 5 systems Bern: 5 systems, Bari: 4 systems Salerno: 4 systems, Bologna: 4 systems Padova: 1 systems Nagoya: 4 systems (75cm2/h) 1 systems (20cm2/h) 5 sub systems (1cm2/h) All system : 20cm2/h  Total 660cm2/h Total 325cm2/h

  14. CS Analysis OPERA film OPERA film To kill BG, 4 hold coincidence !! Emulsion track data consists its position, its slope and its darkness.A real track is selected by the 4-layercoincidence and then validated by its quality. In automatic data selection, Track read out Efficiency ~ 75% S/N ~ 1/2 Current Status of CS Now going on

  15. Flow of Location – ECC – TT ECC CS Large area scan~100cm2 Point Scan ~100x100mm2 neutrino emulsion emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion Lead emulsion

  16. y z y x An example of Found Neutrino Event (1) beam ~1.3mm Event: 228913162 Brick: 29373 Type: CC

  17. y z y x An example of Found Neutrino Event (2) beam Event: 228425652 Brick: 16263 Type: CC

  18. y z y x An example of Found Neutrino Event (3) beam Event: 228482662 Brick: 53754 Type: NC

  19. Location Summary:Number of events identified (located) in ECC bricks under microscope ’08 Run only (In 1690 events triggered by Scintilator Target Trackers) Now going on

  20. Long flight decay ：40% q ~10% : In Film Decay~30% : Next Lead Decay θkink > 20mrad pt > 250Mev/c Decay Search – detect kink topology – cτ = 87 micron Kink detection  track angle deference between tau and daughter Short flight decay：60% IP > 5um Min_pt > 250Mev/c ~60% of tauleptonsdecay in the same Lead plate with vertex. IP Kink detection  minimum distance between daughter and vertex point

  21. Decay Search:High resolution to identify the topology of  decay Minimum distance between pairs of tracks from neutrino interaction (data, P>1GeV/c) IP of a decay daughter of  (Monte Carlo) Minimum distance [micron]

  22. x 13.6 (MeV/c) P =  X0 Physical value from ECC1.Momentum measurement by multiple coulomb scattering P(GeV/c) 1/P(GeV/c)-1 0.8GeV/c pion : P =0.79(GeV/c), dP/P =11% 1.5GeV/c pion : P=1.53(GeV/c), dP/P =16%

  23. MC Data Energy determination by calorimetric method @ a few GeV Test exp. @ CERN (May2001) Physical value from ECC2. Electromagnetic shower

  24.  = 0.98  = 0.54 Physical value from ECC3. Particle ID by dE/dX In Emulsion,dE/dX is defined as darkness of track.  -- Darkness Darkness Momentum-dE/dX 0.87 GeV/c Entry 1063 tracks  P dE/dX (MeV g-1cm2) P   D Particle ID Momentum(GeV/c)

  25. Event# 234539244, Brick# 51248 A charm candidate (1) Decay Pt ~ 460MeV/c • 1ry VTX is PL33. (100960, 52357) • depth=380micron up of film. • 6 tracks found @ PL33. • CharmFlight length : 1330micron.Decay: in Lead (PL33-PL32 )340micron up of PL32.Kink angle : 209mrad. • Daughter Particle : muon (~2.2GeV)IP : 262micron.Decay Pt : ~ 460MeV/c mu+ Kink angle = 209mrad ax ay IP 1. 0.1325 0.0624 (PL33) 6.6  proton 2. 0.0097 -0.0663 (PL33) 4.5 3. 0.0876 0.6656 (PL33) 2.3  1ry mu 4. -0.0390 -0.1354 (PL33) 1.4  charm 5. 0.2215 0.4319 (PL33) 10.3 6. -0.0876 0.0418 (PL31) 18.9  e-pair 7. 0.0893 -0.0638 (PL33) 4.3 Charm Flight Length = 1330micron 1ry muon

  26. A charm candidate (2) pl50 pl51 pl52 pl53 pl54 pl 55 pl 56 pl57 side face Clear kink topology Two EM showers pointing to the vertex Flight length 3247.2 μm kink 0.204 rad Pdaughter 3.9 (+1.7 -0.9) GeV PT 796 MeV 4x10-4 % probability for a hadron re-interaction to have a PT > 600 MeV 7

  27. A Charm candidate (3)

  28. Summary • The goal of OPERA is to detect  oscillation appearance. • OPERA developed Nuclear Emulsion Technology. • In 2008 Run, 1690 neutrino events were triggered in the target tracker.797 vertices were found in ECC bricks under microscope and the search is going on. • From the observation of charm candidates, the ability to detect kink or trident tau decay topologies is proven and its efficiency is being evaluated. • For the run of 2009 that started on June 1, we require 4.5E19 p.o.t. 4300neutrino eventsshould be collected in ECC targets.About 2.5 tau-neutrino interactions are expected to be detected.By 5 years, OPERA will get 10 events. • The OPERA detector suffered no damage following the L’Aquila earthquake.Great thanks to you for the huge support from all over the world!

  29. fin

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