Proc. Neutrino Astrophysics - MPP Theory Group

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34 tank and sphere high purity water will serve as shielding against external gamma rays and as active Cherenkov counter against cosmic muons. The steel sphere will be filled with a tranparent, high purity buffer liquid which itself holds a nylon sphere, filled with organic scintillator. The active scintillator mass will be around 300 t. By means of time of flight measurements event position can be reconstructed and a fiducial volume for solar neutrino interaction defined. The latter should be about 100 t, establishing a counting rate of 55 neutrinos per day according to the standard solar model. The outer part of the scintillator sphere serves as active shielding. The demands on purity in terms of radioactivity in Borexino, especially for the scintillator itself, are very severe. In order to be able to extract a clear signal from background events also in case of total flavour conversion, an intrinsic concentration in Uranium and Thorium of ca. 10 −16 should not be exceeded significantly. The amount of 14 C/ 12 C must not be higher than ≈ 10 −18 . In order to test scintillating materials a large Counting Test Facility (CTF) has been built up in hall C of the underground laboratory at Gran Sasso, which resembles to a small prototyp (ca. 5 t of scintillator) of Borexino. From beginning of 1995 until summer 1997 several tests about the feasibilty of Borexino including procedures to maintain the purity of the scintillator has been performed, which showed very encouraging results: 14 C/ 12 C = 1.85·10 −18 , 238 U = (3.5±1.3)·10 −16 g/g, 232 Th = (4.4±1.5)·10 −16 g/g. A complete discussion of the CTF results including experimental techniques for further background suppression is given in [1] and [2]. Details about the experimental setup of the CTF can be found in [3]. Highly developed neutron activation analysis of scintillation samples performed in Munich is now sensitive in the same regime. For uranium an upper limit of 238 U < 2 ·10 −16 g/g (90% CL) has been obtained. In addition concentration values or limits have been measured by this method for a various amount of isotopes, including man-made nuclei. For details, see [4]. Background studies for Borexino include also the interaction of cosmic muons. The direct detector response on muons has been determined by a coincidence measurement between the CTF and a muon telescope on top of it. The time distribution of such events can be used to discriminate between muon events and neutrino candidates at a level of 98%. However, to reach the sensitivity needed to reach the goals in Borexino, the leak rate for muons must not exceed a level of ≈ 10 −4 . Our design of the muon veto system therefore is threefold: The outer region between external tank and steel sphere acts as Cherenkov counter, a special configuration of the tubes inside the sphere will act as an additional muon identification system, and finally the offline study of event topology like the time structure will help to suppress this kind of background sufficiently. Cosmogenic generation of radioactive nuclei has been sudied this fall at the 180 GeV muon beam at SPS in CERN. Most dangerous source of events will come from 11 C-production in the scintillator and surrounding buffer liquid. However, the energy spectrum of these events is between 1 MeV and 2 MeV since the decay mode is positron decay at 1 MeV endpoint energy. Thus the detection of 7 Be-neutrinos is not affected, however that of pep-neutrinos. Prospects Borexino is an international collaboration of about 60 scientists. Approved funding already comes from INFN (Italy) and from BMBF and DFG (Germany). A substantial part should also be covered by NSF (USA) in the near future. Work on the external tank of Borexino is almost completed. We expect to finish with the inner steel sphere in 1999. Simultaneously the CTF will be upgraded. Finally it will serve as test facility for Borexino scintillator
procurement in batch mode. Given full funding also for our american collaborators first data taking may be expected at the end of the year 2000. References [1] G. Alimonti et al., BOREXINO collaboration, Astr. Phys. J. (1997), accepted for publication [2] G. Alimonti et al., BOREXINO collaboration, Nucl. Phys. (1997), accepted for publication [3] G. Alimonti et al., BOREXINO collaboration, Nucl. Instr. Meth. (1997), accepted for publication [4] T. Goldbrunner et al., Journ. of Rad. Nucl. Chem., 216, (1997) 293. 35
Page 1 and 2: arXiv:astro-ph/9801320v1 30 Jan 199
Page 3: Preface This was the fourth worksho
Page 6 and 7: vi S.J. Hardy Quasilinear Diffusion
Page 8 and 9: viii
Page 11 and 12: History of Neutrino Physics: Pauli
Page 13 and 14: Brief an Oskar Klein, Stockholm, vo
Page 15 and 16: Recent observations with the Hubble
Page 17 and 18: MACHO sample of ∼100,000 light cu
Page 19: Solar Neutrinos
Page 22 and 23: 14 In the depth range where an abun
Page 24 and 25: 16 as follows: (1) All the detector
Page 26 and 27: 18 [3] J.N. Bahcall and H.A. Bethe,
Page 28 and 29: 20 the opacity has a very slowly ch
Page 30 and 31: 22 Status of the Radiochemical Gall
Page 32 and 33: 24 known true source activity. The
Page 34 and 35: 26 Solar Neutrino Observation with
Page 36 and 37: 28 Events/day/kton/bin 0.3 0.25 0.2
Page 38 and 39: 30 log(Δm 2 (eV 2 log(Δm )) 2 (eV
Page 40 and 41: 32 Table 1: Neutrino event rates in
Page 44 and 45: 36 Measurements of Low Energy Nucle
Page 46 and 47: 38 Figure 1: The S(E) factor of 3 H
Page 48 and 49: 40 Solar Neutrinos: Where We Are an
Page 50 and 51: 42 [9] B. Pontecorvo, Chalk River R
Page 52 and 53: 44 Figure 2: The difference between
Page 55 and 56: Phenomenology of Supernova Explosio
Page 57 and 58: Figure 2: Theoretical classificatio
Page 59 and 60: Supernova Rates Bruno Leibundgut Eu
Page 61 and 62: galaxies, however, and the statisti
Page 63 and 64: Figure 1: The motions of pulsars re
Page 65 and 66: Convection in Newly Born Neutron St
Page 67 and 68: a b Figure 2: Panel a shows the rec
Page 69 and 70: ference). The angular variations of
Page 71 and 72: Figure 1: Neutrino luminosity and e
Page 73 and 74: [9] G.S. Bisnovatyi-Kogan, Astron.
Page 75 and 76: and the mass-to-luminosity ratio of
Page 77 and 78: Figure 1: Time variation of superno
Page 79 and 80: Figure 3: Energy spectra of the sup
Page 81 and 82: Supernova Neutrino Opacities G.G. R
Page 83 and 84: Quasilinear Diffusion of Neutrinos
Page 85 and 86: Assuming a saturated thermal distri
Page 87 and 88: Anisotropic Neutrino Propagation in
Page 89 and 90: So far the damping rate corresponds
Page 91 and 92: Cherenkov Radiation by Massless Neu
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on ω so that they are well approxi
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2 2 / meff,e m eff 1.0 0.5 0.0 elec
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Gamma-Ray Burst Observations D.H. H
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Figure 1: The cumulative distributi
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[7] Lilly, S., in Critical Dialogue
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) Phase Transitions in Neutron Star
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after the collapse began (nb., no e
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Models of Coalescing Neutron Stars
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Figure 2: Contour plots of the mass
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From our torus models we find that
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High-Energy Neutrinos
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110 in gamma-rays. However, the acc
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112 Atmospheric Muons and Neutrinos
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114 Today, however, charm productio
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116 Atmospheric Neutrinos in Super-
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118 number of events 300 200 100 (a
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120 Acknowledgements D.K. is suppor
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122 Key signatures for νµ nucleon
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124 (a.u) 0.5 0.4 0.3 0.2 0.1 0 0 1
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126 However, in order to operate th
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128 could be gravitationally captur
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130 Ground-Based Observation of Gam
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132 Figure 2: Sensitivities in unit
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134 Crab flux Figure 4: Gamma-ray f
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136
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Helium Absorption and Cosmic Reioni
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Non-Standard Big Bang Nucleosynthes
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) Non-standard Neutrino Properties
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some heating of the plasma. In cont
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Big Bang Nucleosynthesis With Small
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Neutrinos and Structure Formation i
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Photon and Neutrino Backgrounds The
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The (photon) temperature at aeq is
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spectrum has therefore changed to 1
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Figure 4: Growth of structure in CD
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Future Prospects
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162 Figure 1: Calorimetric β − s
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164 References [1] F. Gatti: Procee
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166 The frequency of Galactic super
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168 Table 1: Comparison of proposed
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170 Neutrinos in Astrophysics José
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172 N eq 7 6.5 6 5.5 5 4.5 4 3.5 3
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174 Figure 4: SN 1987A bounds on FC
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176 [5] A. Joshipura and J. W. F. V
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178 Some Neutrino Events of the 21s
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180 2099: Relic Neutrinos And last
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182
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184 Tuesday, Oct. 21: Supernova Neu
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186 Michael Altmann Technische Univ
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188 Paolo Gondolo Max-Planck-Instit
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190 Patrizia Meunier Max-Planck-Ins
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192 Torsten Soldner Technische Univ
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194 A Experimental Particle Physics
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196 C Astrophysics and Cosmology C1
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