[en] In order to study the inelastic nucleon-nucleon channels producing more than two pions, and to search for isospin 2 dibaryons, the cross-section and the analyzing power versus the missing mass for the pp → π^- X reaction were measured at 1.45, 2.1 and 2.7 GeV incident energies. The missing mass range extends from 1.8 to 2.65 GeV. Any π NN bound state was observed below the π NN threshold in the limit of 8 nbarn/sr around a 2.0 GeV missing mass. A weakly excited structure 15 MeV FWHM was observed, at 2.1 GeV incident energy for a 2.164 GeV missing mass, close to the mass of a nucleon and a delta. The corresponding number of standard deviations is too low to establish clearly its existence. Any narrow resonance was observed above the threshold with an upper limit of 90 nbarn/sr.MeV (3σ) around 2.2 GeV missing mass. The data analysis in phase space terms showed that as incident energy increases, one has to take into account the process N*N besides the usual processes Nδ and δδ

[en] A few topics of narrow structures in nuclear physics at excitation energies of several hundred MeV are overviewed. Among these topics, the physics of dibaryons is particularly interesting since if narrow structures are observed, they can be related to precursor partial quark deconfinement. This possibility simulated the large number of data corresponding to such studies. A brief literature survey of these studies is given. The studies and recent data included in this overview are: analyzing powers in nucleon-nucleon elastic scattering, the p(d,pp)X reaction (X being the two proton missing masses), the ²H(p,n)X⁺⁺ reaction, and dibaryon searches from photonuclear reactions. (R.P.) 39 refs., 6 figs

[en] Experimental evidence for narrow structures at well defined masses in the T = 1 dibaryon sector is discussed. The evidence is not strong enough for the T = 0 or 2 dibaryons and for tribaryons. Experimental requirements needed in order to better understand the structures, e.g., angular distributions for excited T1 baryons and experiments in pure T = 0, 2, and 3 states and in the tribaryon sector, are summarized. Theoretical studies are needed to specify masses and widths of multibaryonic states, as well as dynamical calculations of the relative size of the multibaryon signal and of the background to explain why the structures appear for different reactions and incident energies. Narrow structures are really observed. Their identification with quark degrees of freedom remains the simplest explanation

[en] Missing mass spectra from ³He(p,d)X at Tsub(p)=.75 GeV (thetasub(lab) = 22⁰, 32⁰ and 40⁰) and Tsub(p) = .925 GeV (thetasub(lab) = 30⁰, 40⁰) have been measured. Missing mass spectra from p(³He, d)X at T₃sub(He) = 2.7 GeV and thetasub(lab)=18⁰ have also been measured. The experiments have been carried out with a high missing mass resolution in order to detect possible narrow structures associated with B=2, T=1 quantum numbers. Such structures have been found whose masses and withs are given in the text. The masses of the narrow structures are shown to agree with a rotational like mass formula M=M₀ + M₁ J(J+1), J being the associated spin. The observed peaks might be related to six quark states

[en] The experimental evidence for narrow dibaryons has an essential importance if it can be associated to quark degrees of freedom in nuclei. The difficulty is double: first the corresponding structures have to be observed. Second when observed these structures have to be dissociated as much as possible from any classical explanation as for example a threshold effect corresponding to the opening of a new channel of mesons and two baryons in interaction. Extensive researches are done in some laboratories with emphasizes on the accuracy of the data: only such data, achieved in the two last years will be presented here. The solution of the first difficulty needs data of high precision, both statistical and systematic. The second point: the identification of data with quark degrees of freedom is before all a theoretical problem although it will be clearly favoured by the narrowness of the observed dibaryons. In opposition to experimental investigations for T = 1 and T = 2 dibaryons, where many experiments have been accomplished, there have been no data concerning pure isoscalar dibaryon search. Experimentally evidence for isovector dibaryons has been strengthened, especially in the range above M = 2 M_N + M_π. Intensive works are presently carried out below this threshold. There is still no signature in the isoscalar dibaryon sector. Different experiments have been accomplished in the search of T = 2 narrow dibaryons, at Saturne, Triumf and Lampf, but in any case a narrow structure has been observed

[en] The missing-mass spectra for the ³He(p,d)X reaction (B_x = 2, T_x = 1) have been measured at T_p = 1.2 GeV for θ_d = 33⁰. Narrow structures have been observed at M_x = 2.122, 2.198 and possibly 2.233 GeV with FWHM respectively equal to 5.2, 8.1 and 13 MeV. These results which were obtained in new kinematical conditions, confirm our previous data

[en] The author pointed out that research is needed for regulatory decision making and that as final users of research, regulators should make sure that their needs are accounted for in the programmes. The experience of other regulatory bodies that are involved with the definition of research programmes was mentioned, together with specific examples of safety research themes and noting the importance of having experimental facilities. (author)

[en] The results of recently performed experiments on the B=2 structures concerning the 0,1 and 2 isospin different states are presented. Experimental data and theoretical models are considered. In the T=1 channel, the existence of narrow states, above the πNN threshold, is established. The results from T=0.2 channels are quite difficult to analyse. Present calculations do not allow the prediction of which of the observables are affected by such structures

[en] The experimental situation concerning the hunting of narrow non strange dibaryons is presented and discussed. These have not been firmly observed, up to now, in isospin T = 0 and T = 2 channels, contrary to the situation in T = 1 channel where the existence of such dibaryons is now experimentally well established

[en] This article describes the accident and its consequences and reviews the preliminary steps that have been drawn from it by the French Authority of Nuclear Safety (ASN). First of all, a similar accident is excluded in France because of geographical reasons, so no immediate emergency measures need to be taken but an assessment of the safety of nuclear facilities for the same kinds of risks has to be done rapidly. 3 main points have to be included in this assessment for each facility. First a review of the conformity to the initial safety requirements, secondly the resistance to events overdoing what the facility was designed to stand for, and the feasibility of any modification susceptible to improve the safety of the facility. (A.C.)