Proc. Neutrino Astrophysics - MPP Theory Group

More documents

Recommendations

Info

22 Status of the Radiochemical Gallium Solar <strong>Neutrino</strong> Experiments Michael Altmann Physik Department E15, Technische Universität München, D–85747 Garching and Sonderforschungsbereich 375 Astro-Particle Physics With the successful completion of Gallex after six years of operation and the smooth transition to Gno a milestone in radiochemical solar neutrino recording has been reached. The results from Gallex, 77 ±6±5SNU, and Sage, 74 +11 −10 +5 −7 SNU, both being significantly below all solar model predictions, confirm the long standing solar neutrino puzzle and constitute an indication for non-standard neutrino properties. This conclusion is validated by the results of 51Cr neutrino source experiments which have been performed by both collaborations and 71As doping tests done in Gallex. GALLEX and SAGE: Radiochemical Solar <strong>Neutrino</strong> Recording The radiochemical gallium detectors, Gallex and Sage, have been measuring the integral solar neutrino flux exploiting the capture reaction 71 Ga + νe → 71 Ge + e − . The energy threshold being only 233keV, this reaction allows to detect the pp-neutrinos from the initial solar fusion step which contribute about 90% to the total solar neutrino flux. In a typical run the target, consisting of 30tons of gallium in the form of 101t GaCl3 solution for Gallex and 55t of metallic gallium for Sage, is exposed to the solar neutrino flux for 3-4 weeks. In the following I will mainly focus on Gallex, as for Gallex and Sage the experimental procedure – apart from the chemical extraction of the neutrino produced 71 Ge and the stable germanium carrier which is added at the beginning of each run – is rather similar. Both experiments use the signature provided by the Auger electrons and Xrays associated with the decay 71 Ge + e − → 71 Ga + νe for identification of 71 Ge during a several months counting time. Referring to [4, 5] for a detailed description of the detector setup and experimental procedure I concisely summarize the Gallex experimental program in table 1. Table 1: GALLEX experimental program. It comprises 4 periods of solar neutrino observations (Gallex 1 – Gallex 4), two chromium neutrino source experiments (Source I and Source II) and the arsenic test. date exposure period number of runs result 5/91–4/92 Gallex I 15 solar + 5 blank 81 ± 17 ± 9 SNU 8/92–6/94 Gallex II 24 solar + 22 blank 75 ± 10 +4 −5 SNU 6/94–10/94 Source I ( 51Cr) 11 source runs R = 1.01 +0.11 −0.10 10/94–10/95 Gallex III 14 solar + 4 blank 54 ± 11 ± 3 SNU 10/95–9/96 Source II ( 51Cr) 7 source runs R = 0.84 +0.12 −0.11 9/96–1/97 Gallex IV 12 solar + 5 blank 118 ± 19 ± 8 SNU 1/97–3/97 71As-test 4 arsenic runs Y = 1.00 ± 0.03
The combined result of all 65 Gallex solar runs is 76.4 ± 6.3 +4.5 −4.9 SNU. We note, however, that for the Gallex-IV period pulse shape information is used only for K-peak signals. The present result from Sage, 74 +11 −10 +5 −7 SNU [7], is in perfect agreement with Gallex. The overall results from both experiments are only about 60% of the predictions from solar model calculations, which constitutes an indication for non-standard neutrino properties, even without considering the results from other solar neutrino experiments. The 51 Cr neutrino source experiments In order to validate this conclusion and check the reliability and efficiency of their detectors, both collaborations have prepared intense (≈ 2MCi (Gallex) and 517kCi (Sage)) 51 Cr neutrino sources by neutron irradiating isotopically enriched Cr [3]. 51 Cr decays by EC and emits neutrinos of energy 750keV (decay to g.s., 90%) and 430keV (decay to 320keV excited level, 10%), nicely accommodating the neutrino energies of the solar 7 Be branch. For Gallex, the source has been inserted in the central tube of the target tank. Altogether 18 extractions have been performed with the source in place, divided into two series of measurements with the source being re-activated in between. Figure 1 shows the individual run results. Figure 1: Individual run results of the GALLEX chromium neutrino source experiments, normalized to the known source activity, as a function of time after the end of neutron irradiation of the source. The horizontal bars indicate the durations of the exposures, the exponential curve the expectation from the decay of the source. Source I and Source II runs are represented by circles and diamonds, respectively. An analysis of Source I and Source II yields R = 1.01 +0.11 +0.12 −0.10 and R = 0.84 −0.11 , respectively, where R is the source activity as deduced from the neutrino measurement normalized to the 23
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 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 42 and 43: 34 tank and sphere high purity wate
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
Page 93 and 94:
on ω so that they are well approxi
Page 95:
2 2 / meff,e m eff 1.0 0.5 0.0 elec
Page 99 and 100:
Gamma-Ray Burst Observations D.H. H
Page 101 and 102:
Figure 1: The cumulative distributi
Page 103 and 104:
[7] Lilly, S., in Critical Dialogue
Page 105 and 106:
) Phase Transitions in Neutron Star
Page 107 and 108:
after the collapse began (nb., no e
Page 109 and 110:
Models of Coalescing Neutron Stars
Page 111 and 112:
Figure 2: Contour plots of the mass
Page 113 and 114:
From our torus models we find that
Page 115:
High-Energy Neutrinos
Page 118 and 119:
110 in gamma-rays. However, the acc
Page 120 and 121:
112 Atmospheric Muons and Neutrinos
Page 122 and 123:
114 Today, however, charm productio
Page 124 and 125:
116 Atmospheric Neutrinos in Super-
Page 126 and 127:
118 number of events 300 200 100 (a
Page 128 and 129:
120 Acknowledgements D.K. is suppor
Page 130 and 131:
122 Key signatures for νµ nucleon
Page 132 and 133:
124 (a.u) 0.5 0.4 0.3 0.2 0.1 0 0 1
Page 134 and 135:
126 However, in order to operate th
Page 136 and 137:
128 could be gravitationally captur
Page 138 and 139:
130 Ground-Based Observation of Gam
Page 140 and 141:
132 Figure 2: Sensitivities in unit
Page 142 and 143:
134 Crab flux Figure 4: Gamma-ray f
Page 144 and 145:
136
Page 147 and 148:
Helium Absorption and Cosmic Reioni
Page 149 and 150:
Non-Standard Big Bang Nucleosynthes
Page 151 and 152:
) Non-standard Neutrino Properties
Page 153 and 154:
some heating of the plasma. In cont
Page 155 and 156:
Big Bang Nucleosynthesis With Small
Page 157 and 158:
Neutrinos and Structure Formation i
Page 159 and 160:
Photon and Neutrino Backgrounds The
Page 161 and 162:
The (photon) temperature at aeq is
Page 163 and 164:
spectrum has therefore changed to 1
Page 165 and 166:
Figure 4: Growth of structure in CD
Page 167:
Future Prospects
Page 170 and 171:
162 Figure 1: Calorimetric β − s
Page 172 and 173:
164 References [1] F. Gatti: Procee
Page 174 and 175:
166 The frequency of Galactic super
Page 176 and 177:
168 Table 1: Comparison of proposed
Page 178 and 179:
170 Neutrinos in Astrophysics José
Page 180 and 181:
172 N eq 7 6.5 6 5.5 5 4.5 4 3.5 3
Page 182 and 183:
174 Figure 4: SN 1987A bounds on FC
Page 184 and 185:
176 [5] A. Joshipura and J. W. F. V
Page 186 and 187:
178 Some Neutrino Events of the 21s
Page 188 and 189:
180 2099: Relic Neutrinos And last
Page 190 and 191:
182
Page 192 and 193:
184 Tuesday, Oct. 21: Supernova Neu
Page 194 and 195:
186 Michael Altmann Technische Univ
Page 196 and 197:
188 Paolo Gondolo Max-Planck-Instit
Page 198 and 199:
190 Patrizia Meunier Max-Planck-Ins
Page 200 and 201:
192 Torsten Soldner Technische Univ
Page 202 and 203:
194 A Experimental Particle Physics
Page 204:
196 C Astrophysics and Cosmology C1
show all

Proc. Neutrino Astrophysics - MPP Theory Group

Create successful ePaper yourself

Delete template?

Save as template?