[en] We give a status report on the present neutrino experiments at accelerators (NOMAD, CHORUS, NuTeV, LSND, KARMEN) and at reactors (CHOOZ, Palo Verde, MUNU). The emphasis is put on oscillation searches, but other physics topics are also briefly reviewed

[en] The author presents the researches that have been effected in order to prove the neutrino existence and to find its properties until its discovery in 1956

[en] This is a lecture given at the Gif Summer School held in 1992 in Montpellier. It contains three chapters. These are devoted to neutrino oscillations, to the nuclear reactors used as neutrino sources, and to the experiments performed with neutrinos from nuclear reactors, respectively. The first chapter offers a theoretical frame, the second discusses the investigation capabilities of nuclear reactors as neutrino sources while the last one describes the experimental aspects. These aspects are related to the neutrino flux measurement and the flavor oscillation, the search for neutrino oscillation, the neutrino scattering on electrons, the neutrino decay, the coherent neutrino scattering on nuclei and the electron neutrino-electron antineutrino oscillations implied by the Majorana nature of neutrinos. In concluding the author points to the possible ways of refining these extremely subtle experiments, which will be approached in the near future. 117 refs., 9 figs., 11 tabs

[en] For the first time in one detector measurements were made of the complete decay angular distribution on Y* → Λπ, Λ → pπ^- in the two line-reversed reactions: π⁺p → K⁺Y*(1385) and K^-p → π^-Y*(1385). The experiment was conducted in the SLAC 1 m rapid cycling bubble chamber (15 Hertz) triggered by electronic detectors and an online algorithm. The extended maximum likelihood method was used to obtain the transversity amplitudes of the Y *(1385). Results are in good agreement with both the quark model and Stodolsky-Sakurai model predictions. Finite helicity nonflip contributions at the Y*vertex observed in these data can be associated with double quark scattering in the forward direction. 15 references

[en] In the framework of the 1991/12/30 french law on the management of the nuclear industry waste, the French Atomic Energy Commission (C.E.A.) studies potential benefits against seismic risk of the subsurface domain for the design of an interim storage installation. Indeed, few damage has been observed on subsurface structures during large earthquakes which implied major destructive effects on surface buildings, as during the 1995 Kobe earthquake. However, knowledge on seismic design for subsurface facilities is mainly based on empirical know- how, without satisfactory scientific background which could allow characterization of any given site seismic wave attenuation with depth. The SISPRO program intends to fulfill this lack with two complementary research axis: data acquisition and analysis at several depths and in/on mountain topographies on one hand, accurate numerical modeling on the other hand. The latter will be useful for the establishment of a methodology able to predict seismic waves amplitude, depending on the geotechnical site characteristics and depth. Data analysis which has already been made, such as attenuation laws with several sites data and depth as a parameter, will be depicted. Numerical modeling is based on a 3-D finite differences method able to carry computation of synthetics in any kind of geology. A specific research program is devoted to the case when a topography is present. Numerical results show an attenuation which is smaller than the observed one. This implies that the introduction of a strong gradient in the surface layers properties is probably necessary. Perspectives of the SISPRO program until 2006 will be presented, such as strong motion modeling and how to take into account soil-structure interaction. (author)

[en] An atmospheric nuclear explosion, particularly at ground level or at low altitude, generates immediate radiation that is propagated via different modes of energy transfer, i.e.: electromagnetic waves, light and heat, mechanical effects. Late-stage phenomena, such as the formation and propagation of the cloud, follow on after these early effects. The whole range of different effects - including acoustic and seismic waves as well as the products contained in the cloud - can be detected at distances up to several hundred or several thousand km. When the nuclear source is submarine, a shock wave is generated due to the interaction with the medium. According to the depth of the source, a gas bubble is created which starts to pulsate. As a result of this effect, the acoustic signal is modulated and then propagated to great distances away from the source, thus enabling identification of the explosive phenomenon in the water column. In the case of underground explosions, it is possible to establish a complete description of the interaction with the medium. This comprises generation and propagation of the shock wave, creation of the cavity, zonation of explosion effects, vent collapse, etc. The influence of depth on crater formation, subsidence and decoupling is also discussed. (authors)

[en] We show that comparisons between different reactor experiments do not presently allow to unambiguously prove or disprove neutrino oscillations. Requirements for new generation experiments are deduced from Monte Carlo studies. Finally, the present status and prospects of the Bugey experiment are given. 8 refs

[en] This article describes the different milestones in the story of neutrinos. In 1914 J. Chadwick discovered that the electron emitted in beta-decay does not take away all the energy available. In 1930 W.Pauli postulated the existence of a particle that interacts little with matter and that could be emitted in beta-decay. In 1956 F. Reines and his team succeeded in detecting neutrinos in an experiment installed near the Savannah river reactor. Since then a series of surprises concerning neutrinos stunned the world of physics. In 1957 C.S. Wu discovered the breaking of parity in beta-decay. The second surprise occurred in 1963 when particle accelerators began to produce neutrinos that did not come from beta-decays but from pion decays, these neutrinos were different because they never produced electrons when reacting with other particles, the second family of neutrinos was discovered. The third surprise is that experimental results show that the number of solar neutrinos seems to be less important than expected. A hypothesis is that the electron-neutrinos (the only ones that have been detected) produced in the sun turned into muon-neutrino during their way to earth. A series of experimental results (Gallex, Super-Kamiokande, SNO) suggests the existence of oscillations but the scientific community would like to confirm this hypothesis by using a better controlled source of neutrinos than the sun. Different projects have been launched. (A.C.)

[en] Neutrino properties, and specially their masses, are a central problem for the grand-unified theories of particle physics and for cosmology (structure formation and dark matter). After an historical introduction, we review the main experimental efforts on the ν mass determination: direct measurements, search for neutrinoless double β decays, and finally the search for neutrino flavor oscillations, for which some evidences already exist. (author)

[en] π^-p elastic scattering is studied at an incident π^- beam momentum of 3.92 GeV/c. From the analysis of about 38000 elastic events the differential cross-section for -t>0.06(GeV)² are given. The known structures at -t approximately 0.8 and 2.8(GeV)² are seen. An additional possible structure is present in the backward hemisphere