Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
Figure 2.2: Solar neutrino spectrum and thresholds of solar neutrino experiments as
indicated above the figure (taken from http://www.sns.ias.edu/ jnb/).
2.1.2 The radiochemical detector experiments
Historically, the first solar neutrino experiment was the Homestake experiment
designed by Davis. It opened the way to the astrophysical detection of neutrinos.
The Homestake experiment
The Homestake Experiment (sometimes referred to as the Davis Experiment) was
an experiment headed by astrophysicists Davis and Bahcall in the late 1960s [45].
Its purpose was to collect and count neutrinos emitted by nuclear fusion taking
place in the Sun. Bahcall did the theoretical calculations and Davis designed
the experiment. The experiment took place in the Homestake Gold Mine in
Lead, South Dakota. A 100,000 gallon tank of perchloroethylene was placed 1
mile underground 2 . A big target deep underground was needed to account for
the very small probability of a successful neutrino capture, and to shield from
atmospheric backgrounds. The process
νe + 37 Cl → 37 Ar + e − . (2.1)
transforms a chlorine atom into a radioactive isotope of argon, which can then
be extracted using chemical methods and counted in proportional counters. The
energy threshold of reaction (2.1) is 0.814 MeV, so only the 8 B and 7 Be and pep
neutrinos are detected in the Homestake experiment, the largest contribution
coming from the 8 B neutrinos (see figs. 2.2 and 2.3). The measured capture rate
2 This corresponds to about 615 tons of C2Cl4. Perchloroethylene was chosen because it is
rich in chlorine and because it is a common dry-cleaning fluid.
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