Strangeness production in the Dual Parton model

Production of strange mesons and baryons is studied in a Monte Carlo Dual Parton model for hadron-hadron, hadron-nucleus and nucleus-nucleus collisions with standard strangeness suppression in the chain fragmentation and enhanced strangeness (up to a SU(3) symmetric sea) at the sea chain ends. Additionally, production from the sea has been introduced into the chain formation process with the same probability as for the q→qq branching within the chain fragmentation. Rapidity distributions and multiplicity ratios are in reasonable agreement with recent experimental data.     

The vertex formulation of the Bazhanov-Baxter model

In this paper we formulate an integrable model on the simple cubic lattice. TheN-valued spin variables of the model belong to edges of the lattice. The Boltzmann weights of the model obey the vertex-type tetrahedron equation. In the thermodynamic limit our model is equivalent to the Bazhanov-Baxter model. In the case whenN=2 we reproduce Korepanov's and Hietarinta's solutions of the tetrahedron equation as special cases.     

Fusion of the eight vertex SOS model

A higher spin analogue is presented of the eight vertex-SOS correspondence in the sense of Andrews-Baxter-Forrester. The resulting hierarchy of solvable models contain the hard hexagon model and its recent multi-state generalizations.     

BRST-BFV formalism for the generalized Schwinger model

We derive the Wess-Zumino scalar term of the generalized Schwinger model both in the singular and nonsingular cases by using BRST-BFV framework. The photon propagators are also computed in the extended Lorentz gauge.     

New soluble case of the q-state vertex model

A new solution of the Yang-Baxter equations for the q-state two-dimensional vertex model is found. This solution is valid for arbitrary values of temperature. The partition function of the model is calculated by mapping it on the anisotropic square Ising model.     

Solutions of the reflection equation for the vertex model

We investigate the possible regular solutions of the boundary Yang–Baxter equation for the fundamental U_q[G₂] vertex model. We find four distinct classes of reflection matrices such that half of them are diagonal while the other half are non-diagonal. The latter are parameterized by two continuous parameters but only one solution has all entries non-null. The non-diagonal solutions do not reduce to diagonal ones at any special limit of the free-parameters.     

A microscopic three-cluster model in the hyperspherical formalism

The hyperspherical formalism is applied in the framework of the microscopic generator-coordinate method. Three-cluster systems are described with a single generator coordinate, the hyperradius. This model is a natural extension of previous microscopic theories, and can be applied to bound states and resonances in a range of nuclei exhibiting a cluster structure. As an illustrative example, the model is applied to ⁶He and ⁶Li. Density distributions and electric dipole transition strengths are calculated, including B(E2;0⁺→2⁺) in ⁶He. The results are consistent with a neutron halo structure for the ground state of ⁶He, and with a proton–neutron halo structure of its isobaric analog state in ⁶Li. No 1⁻ “soft dipole” resonance is found in ⁶He.     

Nonlinear sigma model in the Faddeev-Jackiw quantization formalism

The key equations of the symplectic Faddeev-Jackiw formalism are written in an alternative way so that the inverse of the symplectic matrix is easily found. The nonlinear sigma model including the Hopf term in the action is treated in the framework of this quantization method. It is shown how the complete dynamics of the system is described by means of the generalized Faddeev-Jackiw quatum brackets.     

A canonical formalism and its geometric interpretation in the covariant theory of the classical electron

A canonical formalism is constructed for the covariant model of the classical electron proposed in [1, 2, 3]. For the geometric interpretation the notion of the coincidence of the tangent space to the space of outer coordinates with a subspace of the tangent space to the space of inner variables is introduced.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 88–92, June, 1976.In conclusion, the authors wish to thank Yu. G. Borisovich for his constant interest in this work.     

Zero-curvature formalism of supersymmetric principal chiral model

We investigate the one-parameter family of transformations on superfields of the super principal chiral model and obtain different zero-curvature representations of the model. The parametric transformation is related to the super Riccati equations and an infinite set of local and non-local conservation laws is derived. A Lax representation of the model is presented which gives rise to a superspace monodromy operator.Received: 2 July 2004, Revised: 13 October 2004, Published online: 7 December 2004     

Parton distributions in the photon

We discuss in detail the photon structure function beyond the leading logarithm approximation. Of special concern is the factorization scheme and the hadronic input; we show how to naturally absorb large terms due to the factorization scheme in a modified hadronic component. The effect of the charm quark mass threshold is also discussed in relation to the phenomenology. A comparison with data shows that the modified hadronic component can be reasonably described by a VDM-type input.URA 14-36 du CNRS, associée à l'Ecole Normale Supérieure de Lyon, et au Laboratoire d'Annecy-le-Vieux de Physique des Particules     

Three-dimensional vertex model in statistical mechanics from Baxter-Bazhanov model

We find that the Boltzmann weight of the three-dimensional Baxter-Bazhanov model is dependent on four spin variables which are the linear combinations of the spins on the corner sites of the cube, and the Wu-Kadanoff-Wegner duality between the cube- and vertex-type tetrahedron equations is obtained explicitly for the Baxter-Bazhanov model. Then a three-dimensional vertex model is obtained by considering the symmetry property of the weight function, which corresponds to the three-dimensional Baxter-Bazhanov model. The vertex-type weight function is parametrized as the dihedral angles between the rapidity planes connected with the cube. We write down the symmetry relations of the weight functions under the actions of the symmetry groupG of the cube. The six angles with a constraint condition appearing in the tetrahedron equation can be regarded as the six spectra connected, with the six spaces in which the vertextype tetrahedron equation is defined.     

Parton distributions for the LHC

We present updated leading-order, next-to-leading order and next-to-next-to-leading order parton distribution functions (“MSTW 2008”) determined from global analysis of hard-scattering data within the standard framework of leading-twist fixed-order collinear factorisation in the [`(MS)]\overline{\mathrm{MS}} scheme. These parton distributions supersede the previously available “MRST” sets and should be used for the first LHC data taking and for the associated theoretical calculations. New data sets fitted include CCFR/NuTeV dimuon cross sections, which constrain the strange-quark and -antiquark distributions, and Tevatron Run II data on inclusive jet production, the lepton charge asymmetry from W decays and the Z rapidity distribution. Uncertainties are propagated from the experimental errors on the fitted data points using a new dynamic procedure for each eigenvector of the covariance matrix. We discuss the major changes compared to previous MRST fits, briefly compare to parton distributions obtained by other fitting groups, and give predictions for the W and Z total cross sections at the Tevatron and LHC.