Results on 40 A GeV/c PbPb collisions from the NA57 experiment

The NA57 experiment has been designed to study the onset of the strange baryon and antibaryon enhancements in PbPb with respect to p-Be collisions, first observed by WA97 at 160 A GeV/c. NA57 has extended the WA97 measurements to investigate the evolution of strangeness enhancement over a wider centrality range and as a function of the beam energy. Results on hyperon production in central PbPb collisions at 40 A GeV/c are presented and compared with those obtained at higher energy, in the same centrality range

Relationship between the mineralogical composition of the clay fraction of some andalusian caracteristic soils and theri behaviour in relation to potassium

12 páginas, 7 figuras, 3 tablas, 7 referencias.[ES]: Se estudia la fracción arcilla de los suelos más característicos de nuestra región y su comportamiento frente al potasio, relacionándolo con la composición mineralógica de dicha fracción. Exceptuando el suelo fersialítico, los diferentes horizontes de cada suelo no presentan variaciones importantes en su comportamiento frente al potasio. Los suelos vérticos litomorfos y vérticos topomorfos presentan los valores más altos de Kx, lo que está de acuerdo con una mayor edafización y con altas concentraciones de montmorillonita e ilita. El suelo calcimorfo, a pesar de poseer composición mineralógica simlar, está muy poco evolucionado y presenta valores más bajos de Kx, similares a los del suelo aluvial, que está asimismo poco evolucionado, con alta proporción de ilita, a la que acompañan pequeñas proporciones de montmorillonita y caolinita. En el suelo fersialítico lavado disminuye el valor de Kx, al descender en el perfil, en el mismo sentido en que disminuye la ilita y aumenta la montmorillonita. Los horizontes C de los suelos de gran desarrollo edafogenético presentan en relación con los horizontes superiores, a pesar de poseer composición mineralógica similar, valores muy pequeños de Kx. El grado de desarrollo del suelo es el que tiene mayor influencia en los valores de Kx. Los tratamientos de eliminación de materia orgánica y/o geles producen un aumento muy apreciable de los valores de Kx.[EN]: The clay fractions of soils caracteristic of western Anclalucía and their behaviour in relation to potassium are studied, and the latter in related to the mineralogical composition of the former. Except the "fersialitico soil" (Rhocloxeralfs), the various horizons of each soil do not present distinct variations in their behaviour in relation to potassium. The "vertisol litomorfo" (chromoxererts) and «topomorfo» (Pelloxererts) soils present the highest values of Kx which agrees with the strong weathering of these soils and their nigh proportions of montmoillonite and illite. The "calcimorfo soil" (Calciorthids) is little weathered and present lower values of Kx, despite its mineralogical composition, which is analogous to the preceding soils. Similarly low values of Kx are obtained for the «aluvial soil» (Xerofluvents), also little weathered, which contains high proportion of illite, with small amounts of montmorillonite and kaolinite. The value of Kx and the proportion of illite for the leached fersialitico soil decrease and the proportion of montmorillonite increases as getting down across the profile. C horizons of soils with high podogenic development present much lower values of Kx than upper horizona, despite the analogy of their mineralogical compositions. The degree of development of soils has the highest influence on Kx, values. Treatments for removing organic matter and/or gels originate important increases in Kx values.Peer reviewe

Long-range angular correlationsof \u3c0, K and p in p\u2013Pb collisions at 1asNN =5.02TeV

Angular correlations between unidentified charged trigger particles and various species of charged associated particles (unidentified particles, pions, kaons, protons and antiprotons) are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV in the transverse-momentum range 0.3<pT<4 GeV/c. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |\u3b7lab|<0.8. Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of pT and in intervals of event multiplicity. In high-multiplicity events, the second-order coefficient for protons, v2p, is observed to be smaller than that for pions, v2\u3c0, up to about pT=2 GeV/c. To reduce correlations due to jets, the per-trigger yield measured in low-multiplicity events is subtracted from that in high-multiplicity events. A two-ridge structure is obtained for all particle species. The Fourier decomposition of this structure shows that the second-order coefficients for pions and kaons are similar. The v2p is found to be smaller at low pT and larger at higher pT than v2\u3c0, with a crossing occurring at about 2 GeV/c. This is qualitatively similar to the elliptic-flow pattern observed in heavy-ion collisions. A mass ordering effect at low transverse momenta is consistent with expectations from hydrodynamic model calculations assuming a collectively expanding system