Experiment Proposal - opera - Infn

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ABSTRACT The OPERA 4 experiment is proposed for an appearance search of ν µ ↔ ν τ oscillations in the parameter region indicated by Super-Kamiokande as the explanation of the zenith dependence of the atmospheric neutrino deficit. OPERA is a long baseline experiment to be located at the Gran Sasso Laboratory in the CNGS 5 neutrino beam from the CERN SPS. The detector design is based on a massive lead/nuclear emulsion target. Nuclear emulsions are used as high resolution tracking devices, for the direct observation of the decay of the τ leptons produced in ν τ charged current interactions. Electronic detectors locate the events in the emulsions. Magnetised iron spectrometers measure charge and momentum of muons. The discovery potential of OPERA originates from the observation of a ν τ signal with very low background level. The direct observation of ν µ ↔ ν τ appearance will constitute a milestone in the study of neutrino oscillations. 4 Oscillation Project with Emulsion-tRacking Apparatus. 5 Cern Neutrino beam to Gran Sasso.
Contents 1 Introduction 5 1.1 Physics motivations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Oscillation searches with long baseline beams . . . . . . . . . . . . . . . . . . . . . . . . 8 1.3 ν τ detection by the ECC technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2 General features of the experiment 12 2.1 Conceptual design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.1.1 τ detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.1.2 Event reconstruction with electronic detectors . . . . . . . . . . . . . . . . . . . . 16 2.2 Detector structure and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2.1 Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2.2 Electronic detectors in the target modules . . . . . . . . . . . . . . . . . . . . . . 20 2.2.3 Muon spectrometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.2.4 Detector operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3 Performance of the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.3.1 Signal detection efficiency and background . . . . . . . . . . . . . . . . . . . . . 24 2.3.2 Signal and sensitivity to oscillations . . . . . . . . . . . . . . . . . . . . . . . . . 25 3 The CNGS neutrino beam 27 3.1 The beam layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.2 SPS operation and proton yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.3 Neutrino spectrum and interaction rate . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4 Beam monitoring at Gran Sasso . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 4 The detector 34 4.1 Detector configuration and choice of baseline options . . . . . . . . . . . . . . . . . . . . 34 4.2 The ECC bricks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 4.2.1 ECC brick structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 4.2.2 Emulsion films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 4.2.3 Emulsion film transportation and erasing procedure . . . . . . . . . . . . . . . . . 49 4.2.4 Lead plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.2.5 ECC brick assembly in the Gran Sasso . . . . . . . . . . . . . . . . . . . . . . . 53 4.3 Target walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.4 Electronic Target Trackers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.4.1 Detector elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.4.2 Detector planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.4.3 Photodetectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.4.4 Readout electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.4.5 Calibration system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4.4.6 Detector production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 4.4.7 Detector assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.5 Muon spectrometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 1
Page 1 and 2: CERN/SPSC 2000-028 SPSC/P318 LNGS P
Page 3: N. Bruski, S. Buontempo, F. Carbona
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 and 54: een searching for old emulsion plat
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Figure 33: Thickness distribution f
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Figure 35: RMS distribution of 472
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Figure 37: Wall support structure.
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ensures a well defined brick positi
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Figure 41: Detail of the brick mani
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The strips are 6.7 m long, 2.6 cm w
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the effective maximal length (for p
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Table 7: Characteristics of the 64-
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photomultiplier to be tested diaphr
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modate from 512 up to 5180 fibres.
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The fast shaper has a high gain in
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The Ethernet capable device provide
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R&D already performed by the MINOS
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Figure 54: Isometric view of the di
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Figure 56: Magnetic field distribut
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RPC layout 8.00 m 8.75 m Figure 58:
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formance, it is presently foreseen
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Figure 61: Drift plane arrangement
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Figure 63: Schematic view of a XPC
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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
Page 241 and 242:
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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