Experiment Proposal - opera - Infn

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We aim at keeping the time needed for erasing within a few weeks, including the re-conditioning of the film at 20 o C and relative humidity of ∼ 60%. During the erasing process the emulsion films must be kept separated from each other, because processing at high temperature and high humidity can make films sticking to each other (the so-called film blocking). For this reason, adequate space is required in the underground laboratory. The transportation of the emulsions is also an issue to be considered. Ground level (sea) transportation is preferable in order to avoid the hadronic components of cosmic rays, which can create black tracks in the emulsions, difficult to be erased by fading. 4.2.4 Lead plates Lead is well suited as passive material of the OPERA ECC bricks due to its high density and short radiation length. The former enhances the neutrino interaction rate and the latter the momentum determination by multiple scattering as well as the electron identification and energy measurement. However, lead has the drawback of being radioactive and creates background tracks in the emulsion films. We performed an extensive search for low radioactivity lead in samples from companies in different countries. Three producers, one in Japan, one in the USA and one in Sweden, were found able to satisfy our requirements. With their samples, background rates of ∼ 10 α tracks and ∼ 50 β tracks per day per cm 2 were measured (see Section 8.1.2). The density of fake tracks created by the mismatching of unrelated low energy segments (from lead plates), can be estimated to be ∼ 1/mm 2 even after seven years, without considering fading. This value is acceptable for the electromagnetic shower analysis described in Section 6.7. The variation of the thickness of laminated lead plates is within acceptable tolerances. This has been shown, for example, in the case of the liquid argon electromagnetic calorimeter of the ATLAS experiment. 8 This lead was laminated in 800 mm wide sheets with a thickness of 1.13 mm by a continuous production process. A feedback measuring system guarantees the stability of the lead thickness. The plate dimensions are 700 mm × 1800 mm. Fig. 33 shows how constant the thickness has been kept in the longitudinal direction (along 1800 mm). Fig. 34 shows the two-dimensional distribution profile of one of the plates. The thickness of each plate is measured every 50 mm. Using the measured distribution, the RMS of the thickness distribution can be calculated for each plate. This value is one of the indicators of the plate quality. Fig. 35 shows the distribution of this value over 472 large plates. In the particularly bad case of Fig. 34 the maximum thickness variation over 100 mm is ∼ 15 µm. The above results indicate that for the OPERA plate size one could aim at only 15 µm/102 mm ∼ 0.15 mrad slope for a wedge-like shape, much lower than the angular resolution obtained with one emulsion film (∼ 1 mrad). We can then conclude that the needed mechanical accuracy can be achieved with currently available production lines. 8 The information and the data on lead plates given in the following have been kindly made available to us by Ph. Schwemling from LPNHE Paris. 50
Figure 33: Thickness distribution for the lead plates of the ATLAS calorimeter. The result was obtained by measuring the attenuation of 100 keV X-rays, giving an accuracy of about 4 µm. The measurements have been taken every 150 mm along the 1800 mm plate length, by averaging the measurement of 7 gauges distributed in the transverse direction. Since emulsion films have a very small distortion even at the edge, the mechanical properties of lead plates at their edges must be accordingly good. These properties depend on the cutting method and post-cutting treatment. Several cutting procedures (shearing, punching, laser or water jet cutting) are under investigation. The total number of lead plates needed for OPERA is about 13 × 10 6 . In order to produce them in two years, a production rate of about 25000 plates per day is required. The process includes laminating the lead, slicing to rolls, cutting to plates and cleaning. Normally, large smelter companies provide leads in rolls of the requested width and thickness. Cutting and cleaning should not take a long time, since a speed of about 1 plate/s can be achieved by automatic machines. After machining and cleaning the 56 lead plates of a brick are set in a box (or package) which is the basic unit for transportation and assembly. The storage place can be at a surface laboratory. The required amount of lead needed for assembly are transported to the underground laboratory daily or weekly. The absence of radioactivity, a lower price and better mechanical properties would make iron a possible option for the brick plates. However, if one wishes to keep the same number of neutrino interactions, about 30% more emulsions are needed to compensate for the difference in density, making the iron option globally more expensive. In addition, iron gives a worse performance for the brick event analysis (momentum measurement and electron identification) and is corroded by water and air, implying the need for adequate surface treatment. Stainless steel could be used, but with a cost about three times 51
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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 and 38: Figure 19: Generated (continuous li
Page 39 and 40: Emulsion Film + 56 (Lead + Emulsion
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: een searching for old emulsion plat
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
Page 91 and 92: Figure 63: Schematic view of a XPC
Page 93 and 94: Figure 64: Acceleration spectrum fo
Page 95 and 96: Figure 65: The OPERA detector shown
Page 97 and 98: Table 9: Number of electronic chann
Page 99 and 100: Adjustable gain Channel 0 Sample &
Page 101 and 102: Trigger OUT IN Discri. Time Ref. PP
Page 103 and 104: 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
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[89] http : //tosca.web.cern.ch/T O
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