K+^+ production in proton-nucleus reactions and the role of momentum-dependent potentials

The production of $K^+$ mesons in proton-nucleus collisions from 1.0 to 2.5 GeV is analyzed with respect to one-step nucleon-nucleon $(NN\to N Y K^+$) and two-step $\Delta$-nucleon $(\Delta N \to K^+ Y N$) or pion-nucleon $(\pi N \to K^+ Y$) production channels on the basis of a coupled-channel transport approach (CBUU) including the kaon final state interactions. The influence of momentum-dependent potentials for the nucleon, hyperon and kaon in the final state are studied as well as the importance of $K^+$ elastic rescattering in the target nucleus. The transport calculations are compared to the experimental $K^+$ spectra taken at LBL Berkeley, SATURNE, CELSIUS, GSI and COSY-J\"ulich. It is found that the momentum-dependent baryon potentials effect the excitation function of the $K^+$ cross section; at low bombarding energies of $\sim$ 1.0 GeV the attractive baryon potentials in the final state lead to a relative enhancement of the kaon yield whereas the net repulsive potential at bombarding energies $\sim$ 2 GeV causes a decrease of the $K^+$ cross section. Furthermore it is pointed out, that especially the $K^+$ spectra at low momenta (or kinetic energy $T_K$) allow to determine the in-medium $K^+$ potential almost model independently due to a relative shift of the $K^+$ spectra in kinetic energy that arises from the acceleration of the kaons when propagating out of the nuclear medium to free space, i.e. converting potential energy to kinetic energy of the free kaon.Comment: 11 pages, LaTeX, including 10 postscript figures, submitted to Eur. Phys. J.

Nature, Origin, and Age Relationships of Landscape Complexes in Southwestern Saskatchewan

Six landscape complexes are recognized in the Cypress Lake (72 F) and Wood Mountain (72 G) areas of southwestern Saskatchewan. The complexes are recognized by their geomorphology, geology, and processes of landscape formation. The relationships of these components are used to determine the relative ages of the complexes. The oldest complex designated “unglaciated bedrock terrain”, consists of mature landscapes developed in Late Cretaceous and Tertiary sediments. It was formed by fluvial and mass wasting processes under Late Tertiary arid to semi-arid climates. A rather similar complex, but with scattered drift residuals - chiefly glacial erratics, is called “bedrock terrain with residual drift”. This complex reflects similar Late Tertiary processes of landscape formation but was later affected by Pleistocene glaciation. A complex called “bedrock terrain and drift” resembles the older complexes except for a veneer of drift and local meltwater channels. Here, effects of the Late Wisconsinan glaciation are restricted to meltwater erosion, and the drift appears to predate this glaciation. The other three landscape complexes are: “first advance drift”, “interlobate drift” and “last advance drift”. These include terrain typical of the parts of the southern prairies covered by the Late Wisconsinan glacier.On observe six ensembles de paysages dans les régions de Cypress Lake (72F) et Wood Mountain (72G). Les ensembles se distinguent par leur géomorphologie, leur géologie et leurs processus de formation. Les liens entre ces composantes ont servi à déterminer l'âge relatif des paysages. L'ensemble le plus ancien se caractérise par son substratum non englacé et est composé de paysages au stade de la maturité édifiés dans les sédiments du Crétacé supérieur et du Tertiaire. Il a été formé sous les climats arides à semi arides du Tertiaire supérieur par des processus fluviatiles et de solifluxion. Le deuxième ensemble est très semblable, mais comprend, lui, des dépôts glaciaires résiduels dispersés, surtout de nature erratique. Cet ensemble rappelle les mêmes processus de formation, mais il a été englacé au Pléistocène. Le troisième ensemble caractérisé par ses dépôts glaciaires ressemble aux ensembles plus anciens, sauf en ce qui a trait au placage de matériel détritique et à la présence de chenaux de fonte. Ici, les effets de la glaciation du Wisconsinien supérieur se limitent à une érosion par l'eau de fonte, car les dépôts glaciaires semblent antérieurs à cette glaciation. Les trois autres ensembles de paysages se caractérisent, respectivement, par des dépôts glaciaires de première avancée, par des dépôts glaciaires interlobaires et, enfin, par des dépôts glaciaires de dernière avancée. Ces paysages renferment des terrains caractéristiques des milieux de la Prairie englacés au Wisconsinien supérieur.Sechs Landschaftseinheiten wurden in den Gebieten von Cypress Lake (72 F) und Wood Mountain (72 G) in Sùdwest-Saskatchewan identifiziert. Die Einheiten unterscheiden sich durch ihre Géomorphologie, Géologie und Prozesse der Landschaftsbildung. Die Beziehungen zwischen diesen Komponenten werden benutzt, urn das relative Alter der Einheiten zu bestimmen. Die atteste Einheit, welche sich durch ihr nicht vereistes anstehendes Gestein auszeichnet, besteht aus Landschaften im Stadium der Reife, die sich in Sedimenten der spàten Kreidezeit und des Tertiàr entwickelt haben. Sie wurde durch fluviale und Masse zerstôrende Vorgànge unter den trockenen bis halbtrockenen Klimas des spàten Tertiàr gebildet. Eine ziemlich àhnliche Einheit, jedoch mit zerstreuten glazialen Ablagerungsruckstanden vor allem erratischer Natur, wird "Gebiet mit anstehendem Gestein und glazialen Ablagerungsruckstanden" genannt. Diese Einheit spiegelt àhnliche Prozesse der Landschaftsbildung im spàten Tertiàr, wurde aber spàter durch die Vereisung im Pleistozàn beeinfluRt. Ein Gebiet mit anstehendem Gestein und AbIa-gerungen gleicht den àlteren Einheiten, abgesehen von einem Schleier von Trummerablagerungen und ortlichen Schmelzwasserkanàlen. Hier scheinen die Auswirkungen der spàt-Wisconsinischen Vereisung sich auf Erosion durch Schmelzwasser zu beschrànken, und die glazialen Ablagerungen scheinen vor dieser Vereisung geschehen zu sein. Die drei anderen Landschaftseinheiten sind: "glaziale Ablagerungen des ersten Vors-tofies", "interlobale glaziale Ablagerungen" und "glaziale Ablagerungen des letzten VorstoBes". Diese Landschaftseinheiten schlieBen Formationen ein, die typisch fur die im spàten Wisconsinum vereisten Teile der Pràrien sind

Sertraline is an effective management option for cholestatic pruritus

A critical appraisal and clinical application of Mayo MJ, Handem I, Saldana S, Jacobe H, Getachew Y, Rush AJ. Sertraline as a first-line treatment for cholestatic pruritus. Hepatology. 2007 Mar;45(3):666-74. doi: 10.1002/hep.2155

Spectral components at visual and infrared wavelengths in active galactic nuclei

Aperture-dependent infrared photometry of active galactic nuclei are presented which illustrate the importance of eliminating starlight of the galaxy in order to obtain the intrinsic spectral distribution of the active nuclei. Separate components of emission are required to explain the infrared emission with a spectral index of alpha approx = 2 and the typical visual-ultraviolet continuum with alpha approx = 0.3 (where F(nu) varies as nu(sup-alpha). Present evidence does not allow unique determination of the appropriate mechanisms, but the characteristics of each are discussed

Sifat-sifat Spektral dan Struktur Kombinatorik pada Sistem Positif 2d

The dynamics of a 2D positive system depends on the pair of nonnegative square matrices thatprovide the updating of its local states. In this paper, several spectral properties, like finitememory, separablility and property L, which depend on the characteristic polynomial of thepair, are investigated under the nonnegativity constraint and in connection with thecombinatorial structure of the matrices.Some aspects of the Perron-Frobenius theory are extended to the 2D case; in particular,conditions are provided guaranteeing the existence of a common maximal eigenvector for twononnegative matrices with irreducible sum. Finally, some results on 2D positive realizationsare presente

Transport analysis of K+ production in proton-nucleus reactions

The production of $K^+$ mesons in proton-nucleus collisions from 1.0 to 2.3 GeV is analyzed with respect to one-step nucleon-nucleon $(NN\to N Y K^+$) and two-step $\Delta$-nucleon $(\Delta N \to K^+ Y N$) or pion-nucleon $(\pi N \to K^+ Y$) production channels on the basis of a coupled-channel transport approach (CBUU) including the kaon final-state-interactions (FSI). Momentum-dependent potentials for the nucleon, hyperon and kaon in the final state are included as well as $K^+$ elastic rescattering in the target nucleus. The transport calculations are compared to the experimental $K^+$ spectra taken at COSY-J\"ulich. Our systematic analysis of $K^+$ spectra from $^{12}C$, $^{63}Cu$, $^{107}Ag$ and $^{197}Au$ targets as well as their momentum differential ratios gives a repulsive $K^+$ potential of $20\pm 5$ MeV at normal nuclear matter density.Comment: 7 pages, 5 figures, submitted to Eur. Phys. J.

On the Delta I = 1/2 rule in the Lambda N ----> N N reaction

It is shown that the mass dependence of the $\Lambda$-lifetime in heavy hypernuclei is sensitive to the ratio of neutron-induced to proton-induced non-mesonic decay rates R_n/R_p. A comparison of the experimental mass dependence of the lifetimes with the calculated ones for different values of R_n/R_p leads to the conclusion that this ratio is larger than 2 on the confidence level of 0.75. This suggests that the phenomenological $\Delta$I=1/2 rule might be violated for the nonmesonic decay of the $\Lambda$-hyperon.Comment: 3 pages, 2 figures, to be published in European Physical Journal