Search

There is a large body of research on software services, but the issues of communication and dynamic reconfiguration have received little attention, as have adaptation to environment and dynamic combination of service building blocks into new applications. Here, we present the approach of the FP7 alive project to the use of formal models of coordination and organisation mechanisms to deliver a flexible, high-level means to describe the structure of interactions between services in the environment. Our aim is to create a framework for services engineering for ˵live″ open systems of active services. We propose to build on the current activities in service-oriented engineering by defining three levels: (i) An organisational level models the organisational structure of executing and interlinked services and the context around them. (ii) A coordination level provides flexible ways to model interaction between the services. (iii) These two levels connect with existing (semantic) Web services, which contain semantic descriptions to make components aware of their social context and of the rules of engagement with other services. [ABSTRACT FROM AUTHOR]

We evaluate semileptonic and two-meson nonleptonic decays of the Bc− meson in the framework of a nonrelativistic quark model. The former are done in spectator approximation using one-body current operators at the quark level. Our model reproduces the constraints of heavy-quark spin symmetry obtained in the limit of infinite heavy-quark mass. For the two-meson nonleptonic decays we work in factorization approximation. We compare our results to the ones obtained in different relativistic approaches. [ABSTRACT FROM AUTHOR]

Working in the framework of a nonrelativistic quark model we evaluate the spectra and semileptonic decay widths for the ground state of doubly heavy Ξ and Ώ baryons. We solve the three-body problem using a variational ansatz made possible by the constraints imposed by heavy-quark spin symmetry. In order to check the dependence of our results on the inter-quark interaction, we have used five different quark-quark potentials which include Coulomb and hyperfine terms coming from one-gluon exchange, plus a confining term. Our results for the spectra are in good agreement with a previous calculation done using a Faddeev approach. For the semileptonic decay our results for the total decay widths are in good agreement with the ones obtained within a relativistic quark model in the quark-diquark approximation. [ABSTRACT FROM AUTHOR]

Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) mesonbaryon chiral Lagrangian by using a scheme which relies on spin-flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)-flavor WT results for the lowestlying s-wave negative-parity baryon resonances, and it also provides some information on the dynamics of the heavier ones. Moreover, it also predicts the existence of an isoscalar spin-parity 3−/2 K* N bound State (strangeness +1) with a mass around 1.7–1.8 GeV, unstable through K* decay. Neglecting d-wave KN decays, this State turns out to be quite narrow (Γ ≤ 15 MeV) and it might provide clear Signals in reactions like νp → ]> 0pK+Π− by looking at the three-body pK+Π− invariant mass. [ABSTRACT FROM AUTHOR]

The construction of an extended version of the Weinberg-Tomozawa Lagrangian, in which baryons and mesons form spin-flavor multiplets, is reviewed and some of its properties discussed, for an arbitrary number of colors and flavors. The coefficient tables of spin-flavor irreducible representations related by crossing between the s-, t- and u-channels are explicitly constructed. [ABSTRACT FROM AUTHOR]

The semileptonic decay B → Π is studied starting from a simple quark model that takes into into account the effect of the B*-resonance. A novel, multiply subtracted, Omnès dispersion relation has been implemented to extend the predictions of the quark model to all q2 values accessible in the physical decay. By comparison to the experimental data, we extract |Vub| = (3.4 ± 0.2(exp.) ± 0.7(theory)) 10−3. As a further test of the model, we have also studied D → Π and D → K decays for which we get good agreement with experiment. [ABSTRACT FROM AUTHOR]

Starting from a consistent SU(6) extension of the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian (Phys. Rev. D 74, 034025 (2006)), we study the s-wave meson-baryon resonances in the strangeness S = −3 and negative-parity sectors. Those resonances are generated by solving the Bethe-Salpeter equation with the WT interaction used as kernel. The considered mesons are those of the 35-SU(6)-plet, which includes the pseudoscalar (PS) octet of pions and the vector (V) nonet of the rho-meson. For baryons we consider the 56-SU(6)-plet, made of the 1/2+ octet of the nucleon and the 3/2+ decuplet of the Delta. Quantum numbers I(JP) = 0(3/2−) are suggested for the experimental resonances ω*(2250)− and ω*(2380)−. Among other, resonances with I = 1 are found, which minimal quark content is sss ]> l', being s the strange quark and l, l' any of the the light up or down quarks. A clear signal for such a pentaquark would be a baryonic resonance with strangeness −3 and electric charge −2 or 0, in proton charge units. We suggest looking for K−Ξ− resonances with masses around 2100 and 2240 MeV in the sector 1(1/2−), and for Π±ω− and K−Ξ*− resonances with masses around 2260 MeV in the sector 1(3/2−). [ABSTRACT FROM AUTHOR]