Experiment Proposal - opera - Infn

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4 The detector 4.1 Detector configuration and choice of baseline options The Progress Report [6] submitted in 1999 to the Scientific Committees outlined the design of an experiment sensitive to ν τ appearance in the parameter region indicated by the atmospheric neutrino signal. Different detector options fulfilling the physics requirements were considered. Our main efforts have since then been devoted to the definition of a baseline experiment design with cost effective solutions and a reduced need for R&D studies. In particular, two different kinds of brick structures were envisaged in [6]: the so-called spacer and compact bricks. The main features of spacer bricks can be found in Section 9 and in [3–6]. Their cell structure includes a low density spacer of 3 mm thickness. The low density material minimises the probability of reinteractions allowing to reduce the corresponding backgrounds. On the other hand, compact bricks have the advantage of a denser brick structure, optimal for the identification of the τ → e decay mode and for the measurement of charged particle momentum by the multiple scattering method. Because of this capability, the hadron reinteraction background in compact bricks can be suppressed by kinematical cuts. For a given emulsion surface, compact bricks also provide a larger target mass and their mechanical rigidity ensures a better parallelism of the emulsion films. The above arguments, together with the existing experience with similar detectors (DONUT), leads us to propose as a baseline option a setup made up of three compact brick supermodules. A total lead mass of about 2 kton can be obtained with a surface of emulsion films similar to what foreseen in [6]. Baseline options have also been identified for the magnet (dipole), for the spectrometer Inner Trackers (RPC detectors), for the spectrometer Precision Trackers (drift tubes) and for the Target Trackers (scintillator strips). In all cases, the decision has been driven by the physics requirements, by consideration of cost effectiveness and by the needs of large scale production and reliable long term <strong>opera</strong>tion. 4.2 The ECC bricks 4.2.1 ECC brick structure About 235000 ECC bricks compose the OPERA detector. A schematic drawing of a brick is shown in Fig. 21. Its structure is obtained by stacking 56 1 mm thick lead plates interleaved with thin emulsion films. Each film has 50 µm thick emulsion layers on both sides of a 200 µm thick plastic base. An extra emulsion film in front of the first lead plate helps in connecting tracks from the upstream wall. Another film, called Special Sheet (SS) is placed at the most downstream part, separated from the 56 th film by a 2 mm thick plastic plate. This allows to preserve the τ decay detection efficiency for events occurring in the last lead plate. The brick-stack is kept together by the so-called origami packing method, a technique used in previous emulsion experiments. A photograph of a prototype brick packed with origami is shown in Fig. 22. The packing material is an aluminum-coated paper closed under vacuum by thermo-sealing. The paper quality is selected in order to avoid chemical contamination which could affect the emulsion sensitivity. 34
Emulsion Film + 56 (Lead + Emulsion Film) + Plastic plate + Emulsion Film (The SS film) 75.4mm ....... 127mm The SS film 2mm 102mm Neutrino Emulsion Film ....... Lead Plate Plastic Plate Emulsion Film Figure 21: Schematic structure of the OPERA ECC brick. 35
Page 1 and 2: CERN/SPSC 2000-028 SPSC/P318 LNGS P
Page 3 and 4: N. Bruski, S. Buontempo, F. Carbona
Page 5 and 6: Contents 1 Introduction 5 1.1 Physi
Page 7 and 8: 6.7.1 Multiple scattering analysis
Page 9 and 10: 1 Introduction In this document we
Page 11 and 12: eactor experiments (KAMLAND [22], B
Page 13 and 14: difference being the nature of the
Page 15 and 16: The total energy of electrons and
Page 17 and 18: through the decay topology and its
Page 19 and 20: Figure 6: Simulated ν τ event wit
Page 21 and 22: particles above 10 MeV . One can se
Page 23 and 24: vertex position as predicted by the
Page 25 and 26: • stability and maintenance: no p
Page 27 and 28: Figure 11: Illustration of the vari
Page 29 and 30: Table 3: Expected numbers of τ and
Page 31 and 32: 3 The CNGS neutrino beam 3.1 The be
Page 33 and 34: per year of operation because the S
Page 35 and 36: ν µ at GS (p.o.t. GeV m 2 ) -1 10
Page 37: Figure 19: Generated (continuous li
Page 41 and 42: The mechanical properties of the fi
Page 43 and 44: Figure 24: Film thickness distribut
Page 45 and 46: contact at different temperature an
Page 47 and 48: Figure 27: Photograph of a minimum
Page 49 and 50: entry : 85 RMS: 0.060 15 10 5 0 0 d
Page 51 and 52: [micron] 2 1 0 -1 -2 [micron] 2 1 0
Page 53 and 54: een searching for old emulsion plat
Page 55 and 56: Figure 33: Thickness distribution f
Page 57 and 58: Figure 35: RMS distribution of 472
Page 59 and 60: Figure 37: Wall support structure.
Page 61 and 62: ensures a well defined brick positi
Page 63 and 64: Figure 41: Detail of the brick mani
Page 65 and 66: The strips are 6.7 m long, 2.6 cm w
Page 67 and 68: the effective maximal length (for p
Page 69 and 70: Table 7: Characteristics of the 64-
Page 71 and 72: photomultiplier to be tested diaphr
Page 73 and 74: modate from 512 up to 5180 fibres.
Page 75 and 76: The fast shaper has a high gain in
Page 77 and 78: The Ethernet capable device provide
Page 79 and 80: R&D already performed by the MINOS
Page 81 and 82: Figure 54: Isometric view of the di
Page 83 and 84: Figure 56: Magnetic field distribut
Page 85 and 86: RPC layout 8.00 m 8.75 m Figure 58:
Page 87 and 88: formance, it is presently foreseen
Page 89 and 90:
Figure 61: Drift plane arrangement
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Figure 63: Schematic view of a XPC
Page 93 and 94:
Figure 64: Acceleration spectrum fo
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Figure 65: The OPERA detector shown
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Table 9: Number of electronic chann
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Adjustable gain Channel 0 Sample &
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Trigger OUT IN Discri. Time Ref. PP
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Super Module 1 Super Module 2 Super
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5 Analysis of the electronic detect
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Track segments on both the emulsion
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5.5 Brick finding efficiency The se
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Wall finding efficiency 1 0.95 0.9
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The worst case leading to the lowes
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electromagnetic showering events an
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Studies on the strategies have star
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which may enter in such a compariso
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Figure 84: The total brick finding
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Figure 86: Charge determination of
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Figure 89: Muon momentum resolution
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Figure 91: Muon momentum resolution
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Reconstructed Pion Energy N Analog
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Figure 98: The difference between r
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By using the above running modes of
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µm EXP.: DONUT 3039/01910 MOD.:ECC
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emulsion film plastic foils and edg
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200micron base 50micron emulsion la
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Figure 106: Tracking efficiency of
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a base track on film 2 a penetratin
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Long decays, defined as a decay top
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more than 60 views/s recognising al
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Table 12: Basic numbers used to des
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an area that one S-UTS can process
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unit cell L=1300micron Pb plate ( 1
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We recall that the intrinsic positi
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Figure 116: The top histograms show
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The error on θ S due to both the s
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Figure 120: Fraction of pions which
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#1 #2 #3 #4 #5 γ γ ∆θ 4= |θ 5
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Figure 124: Energy resolution for e
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Figure 126: Efficiency for γ’s t
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7 Physics performance 7.1 Electron
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7.2 Muon identification efficiency
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Table 13: Muon identification effic
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Table 14: Brick finding efficiency
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The second result is obtained from
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Figure 134: Brick-to-brick connecti
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Figure 136: Distribution of τ deca
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For long decays the overall efficie
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The φ angle is expected to peak at
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Table 19: Summary of the kinematica
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known. Because of these uncertainti
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Table 21: Expected charm background
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π− e+ γ e- e+ e- γ π− Figur
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Table 24: Estimates of the rate of
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Table 27: Expected numbers of τ an
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Table 28: Sensitivity at the 90% CL
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7.6 Determination of the oscillatio
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measurement of the ratio between ν
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Table 30: Neural network recognitio
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(mrad) 0.04 0.02 0 -0.02 -0.04 10 2
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Table 31: Radioactivity measurement
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ick. There is approximately a facto
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Figure 152: A typical PMT response
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1m π, µ 15 GeV/c mini-walls 1.6 m
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Electrons 1GeV/c 20mm Pb Number of
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tube. An Image Intensifier (II) by
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1 0 0 l = 1 1 .8 m N, p.e. 1 0 1 0
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HPD’s pixels (Fig. 162). The cook
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A complete system has been designed
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The acquisition system (VA-DAQ) use
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The upstream tracker T 1-3 between
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Figure 168: Distributions of the ap
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Figure 169: Example of a large-angl
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multiple scattering, given the smal
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9.1.3 Wall support structures An al
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Nevertheless, the possibility to us
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Figure 174: (a) 3D view of the spec
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9 p.e. and 6.9 p.e. at a distance f
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Figure 176: Neutrino induced charm
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A test programme for emulsion brick
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The space requirements in the exper
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advance. The sets of scintillator s
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Task Name Start Finish Study of mai
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11 Experimental infrastructure 11.1
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After the exposure to cosmic rays,
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on the size of these stations. A co
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Table 38: Expected contributions to
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the developed emulsions and to stan
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As the sensitivity is not limited b
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[26] M. Apollonio et al., Phys. Let
Page 269:
[89] http : //tosca.web.cern.ch/T O
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