[en] A source of polarized electrons based on a helium flowing afterglow has been developed at Orsay. This source, SELPO-M, has been placed on a 100 kV platform and set up in such a way as to allow its connection to the MAMI accelerator. Its performances in terms of current, polarization and optical properties are given. Its figure of merit (IP²≅75 μA) appears highly competitive as compared to strained GaAs sources. (author)

[en] The reaction pp→pπ⁺N has been studied at three energies (T_p=1520 , 1805, and 2100MeV) and six angles from 0 degree up to 17 degree (laboratory). Several narrow states have been observed in missing mass spectra at 1004, 1044, and 1094MeV. Their widths are typically 1 order of magnitude smaller than the widths of N^* or Δ . Possible biases are discussed. These masses are in good agreement with those calculated within a simple phenomenological mass formula based on color magnetic interaction between two colored quark clusters. copyright 1997 The American Physical Society

[en] The reaction pp → pπ⁺X was studied at different incident energies around T_p=2 GeV. Narrow baryonic structures were observed in the missing mass M_X and in the invariant mass M_pπ⁺. The masses of these structures are 1004, 1044, 1094, 1136, 1173, 1249, 1277, and 1384 MeV (and possibly 1339 MeV). Some of them were also observed at the same masses in the missing-mass spectra of the dp→ppX reaction although with a weaker signature. Many checks were performed to make sure that these structures were not produced by experimental artifacts. Several narrow small-amplitude peaks, were also extracted using already published photonucleon cross-sections. The small widths of all these results, and the stability of the observed structures, regardless of the experiment, were used to conclude that they are genuine baryons and not merely the consequence of dynamical rescatterings. These baryons cannot be associated with classical q³ quark configurations. We associate them with two colored-quark cluster configurations. (orig.)

[en] Several narrow exotic baryonic states have been recently observed at 1004, 1044, and possibly at 1094 MeV, from the study of pp→pπ⁺X reaction at different energies (T_p=1520, 1805 and 2100 MeV) and angles from 0 deg. up to 17 deg. (lab.). The small widths: a few MeV, indicate a possible interpretation within multiquark baryons or baryonic resonances. A phenomonological mass formula for two clusters of quarks, predicts masses, quite close to the experimental ones

[en] The reaction pp → pπ⁺X has been studied at 3 energies (T_p 1520, 1805 and 2100 MeV) and 6 angles from 0 angle up to 17 angle (lab.). Several narrow states have been observed in missing mass spectra at: 1004, 1044, 1094 MeV. Their widths are typically one order of magnitude smaller than the widths of N^* of Δ. Possible biases are discussed. These masses are in agreement with those calculated within a simple phenomenological mass formula based on color magnetic interaction between two colored quark clusters. (authors)

[en] The reaction p-vectorp → pπ⁺X was studied at three energies(T_p=1520, 1805 and 2100 MeV). The analyzing powers of p-vectorp → ΔΔ, p-vectorp → Δn and p-vectorp → pπ⁺X reactions (0.94< M_x<1.5 GeV) were extracted between 0 and 17 in the lab, which corresponds to an angular range between 0 and 100 (c.m.). A theoretical analysis was performed based on s-channel contributions in 2⁺ and 1^- intermediate states. The resulting formulas allow us to obtain good fits with experimental data. (orig.)

[en] Two reactions, pp→ppX and pp→pπ⁺X, are used to study the 1.47≤M≤1.680 GeV baryonic mass range. Three different final states are considered in the invariant masses: N* or Δ⁺,nπ⁺ or pπ⁰, and pη. The last two channels are defined by software cuts applied to the missing mass of the first reaction. Several narrow structures are extracted with widths σ(Γ) varying between 3 and 9 MeV. Some structures are observed in one channel but not in another. Such nonobservation may be due either to the spectrometer momenta limits or to the physics (e.g., no such disintegration channel is allowed from the narrow state considered).We tentatively conclude that the broad Particle Data Group (PDG) baryonic resonances--N(1520)D₁₃,N(1535)S₁₁,Δ(1600)P₃₃,N(1650)S₁₁, and N(1675)D₁₅--are collective states built from several narrow and weakly excited resonances, each having a (much) smaller width than the one reported by PDG

[en] The reaction p-vectorp→pπ⁺X has been studied at three energies (T_p=1520, 1805 and 2100 MeV), using the Saturne polarized proton beam and the SPES3 experimental facility. The analyzing powers of p-vectorp→Δ⁺⁺Δ⁰, p-vectorp→Δ⁺⁺n and p-vectorp→pπ⁺X reactions have been studied between 0 deg. and 17 deg. in the lab., which corresponds to an angular range between 0 deg. and 100 deg. (c.m.)

[en] The tensor polarization of deuterons, ρ₂₀, emitted at zero degree in the ¹H(³He, d-↔)X reaction, was measured at the Saturne National Laboratory in Saclay, using the SPES4 magnetic channel and the HYPOM polarimeter. The momentum of the detected deuterons was kept fixed at 3.77 GeV/c, while the momentum of the ³He beam was varied from 5.66 to 4.60 GeV/c; this provided a range of internal momenta of a deuteron in ³He, k, from 0 to 0.43 GeV/c

[en] In an earlier experiment some evidence was observed for narrow dibaryons in the analyzing power excitation function of p-p elastic scattering at √s=2160 MeV and 2192 MeV, with width Γ≅13-14 MeV. A different procedure has been carried out at the SATURNE synchrotron, in order to obtain a very high accuracy of the analyzing power for a large number of energies between 510 and 725 MeV. The results show no evidence for any structure with width ∼5 to 20 MeV. The reasons at the difference between the two experiments are discussed. (K.A.) 2 refs., 3 figs