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

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 used 1947 (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. 50 micron Microscopic Image Recorded as silver grains along the line particle passed through Resolution of 0.3 micron 2009 ? First direct observation of    oscillation appearance Sub micron resolution 3D tracking

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.

Conceptual Design   Appearance INFN Gran Sasso CERN SPS 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 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  CC events ~ 2.5/year Here, I will mainly talk about Emulsion Technology and Analysis.

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

How to detect tau neutrino DONUT  event Flight Length：280um   1mm Emulsion Kink   e 18 ％    17 ％   h 49 ％ Trident   3h (h h h) 15 ％ DONUT : Iron 1mm OPERA : Lead 1mm

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

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

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

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

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

Changeable Sheet (CS) ? Roles of CS Two films Easily detached 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 developed In the case a track is NOT found  Next Brick should be taken out. Refresh: keeping the emulsion films at high relative humidity(98%) and high temperature (30deg C) for 3days. ? Non refresh extraction After refresh Ratio of erasing > 99% 12

Emulsion Data taking – automatic scanning system – Japanese Scanning System European Scanning System Scanning speed/system: 75cm2/h High speed CCD camera (3 kHz) Piezo-controlled objective lens FPGA Hard-coded algorithms Scanning speed/system: 20cm2/h Customized commercial optics and mechanics asynchronous DAQ software 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) Total 325cm2/h All system : 20cm2/h  Total 660cm2/h

Next Brick; now going on 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-layer coincidence and then validated by its quality. In automatic data selection, Track read out Efficiency ~ 75% S/N ~ 1/2 Current Status of CS Number of event 1473 Check done 1440 Found @ CS 1110 Next Brick; now going on 330 Now going on

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

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

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

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

Location Summary: Number of events identified (located) in ECC bricks under microscope ’08 Run only NC CC Total Bricks received in labs 218 959 1177 Bricks measured 195 895 1090 CS to brick connection successful 178 849 1027  interactions located in the bricks 119 678 797 Interaction is upstream wall 12 46 58  interactions in the dead material 4 17 21 (In 1690 events triggered by Scintilator Target Trackers) Now going on

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

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]

Physical value from ECC 1 Physical value from ECC 1.Momentum measurement by multiple coulomb scattering P(GeV/c) P = 13.6 (MeV/c)  X0 x 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%

Physical value from ECC 2. Electromagnetic shower Test exp. @ CERN (May2001) MC Data @ a few GeV Energy determination by calorimetric method

Physical value from ECC 3. Particle ID by dE/dX In Emulsion, dE/dX is defined as darkness of track.  = 0.98  = 0.54  -- 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)

A charm candidate (1) Event# 234539244, Brick# 51248 1ry VTX is PL33. (100960, 52357) depth=380micron up of film. 6 tracks found @ PL33. Charm Flight 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 Decay Pt ~ 460MeV/c mu+ Kink angle = 209mrad Charm 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 Flight Length = 1330micron 1ry muon

A charm candidate (2) side face Clear kink topology 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

A Charm candidate (3)

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. 4300 neutrino events should 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!

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