Hunting spiders of woodland fragments and agricultural habitats in the Atlantic rain forest region of Brazil

The hunting spider communities of the Dionycha clade were studied 1986 through 1988 in fragmented woodlands and secondary agricultural habitats of the Botucatu area in São Paulo state, Brazil. The original vegetation of mainly tropical Atlantic rain forest (Mata Atlantica) was cleared already 70 years ago. In a total sample of over 1000 adult spiders, 247 species belonging to 12 families Mere determined. A decreasing frequency and diversity of spiders rc as found if forest remnants were compared with sugar cane fields and cattle pasture. The specific composition of the spider fauna as surveyed in different habitats is discussed under ecological aspects and in relation to the history of land use.

Vector and axial-vector correlators in a non-local chiral quark model

The behavior of the non-perturbative parts of the isovector-vector and isovector and isosinglet axial-vector correlators at Euclidean momenta is studied in the framework of a covariant chiral quark model with non-local quark-quark interactions. The gauge covariance is ensured with the help of the P-exponents, with the corresponding modification of the quark-current interaction vertices taken into account. The low- and high-momentum behavior of the correlators is compared with the chiral perturbation theory and with the QCD operator product expansion, respectively. The V-A combination of the correlators obtained in the model reproduces quantitatively the ALEPH and OPAL data on hadronic tau decays, transformed into the Euclidean domain via dispersion relations. The predictions for the electromagnetic pi(+/-) - pi(0) mass difference and for the pion electric polarizability are also in agreement with the experimental values. The topological susceptibility of the vacuum is evaluated as a function of the momentum, and its first moment is predicted to be chi'(0) approximate to (50 MeV)(2). In addition, the fulfillment of the Crewther theorem is demonstrated.

The omega DD vertex in a sum rule approach

The study of charmonium dissociation in heavy ion collisions is generally performed in the framework of effective Lagrangians with meson exchange. Some studies are also developed with the intention of calculate form factors and coupling constants related with charmed and light mesons. These quantifies are important in the evaluation of charmonium cross sections. In this Letter we present a calculation of the omega DD vertex that is a possible interaction vertex in some meson-exchange models spread in the literature. We used the standard method of QCD sum rules in order to obtain the vertex form factor as a function of the transferred momentum. Our results are compatible with the value of this vertex form factor (at zero momentum transfer) obtained in the vector-meson dominance model. (c) 2006 Elsevier B.V. All rights reserved.

Hadronic form factors and the J/psi secondary production cross section: An update

Improving previous calculations, we compute the D + (D) over bar J/psi + pi cross section using the most complete effective Lagrangians available. The new crucial ingredients are the form factors on the charm meson vertices, which are determined from QCD sum rules calculations. Some of them became available only very recently, and the last one, needed for our present purpose, is calculated in this work.

Cutoff-independent regularization of four-fermion interactions for color superconductivity

We implement a cutoff-independent regularization of four-fermion interactions to calculate the color-superconducting gap parameter in quark matter. The traditional cutoff regularization has difficulties for chemical potentials mu of the order of the cutoff Lambda, predicting in particular a vanishing gap at mu similar to Lambda. The proposed cutoff-independent regularization predicts a finite gap at high densities and indicates a smooth matching with the weak coupling QCD prediction for the gap at asymptotically high densities.

Renormalized new solutions for the massless Thirring model

We present a nonperturbative study of the (1 + 1)-dimensional massless Thirring model by using path integral methods. The regularization ambiguities - coming from the computation of the fermionic determinant - allow to find new solution types for the model. At quantum level the Ward identity for the 1PI 2-point function for the fermionic current separates such solutions in two phases or sectors, the first one has a local gauge symmetry that is implemented at quantum level and the other one without this symmetry. The symmetric phase is a new solution which is unrelated to the previous studies of the model and, in the nonsymmetric phase there are solutions that for some values of the ambiguity parameter are related to well-known solutions of the model. We construct the Schwinger-Dyson equations and the Ward identities. We make a detailed analysis of their UV divergence structure and, after, we perform a nonperturbative regularization and renormalization of the model.

Measurement of the isolated photon cross section in p(p)over-bar collisions at root s=1.96 TeV

The cross section for the inclusive production of isolated photons has been measured in p (p) over bar collisions at root s = 1.96 TeV with the DO detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity vertical bar n vertical bar < 0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties. (c) 2006 Elsevier B.V. All rights reserved.

Coulomb gauge quark model, vacuum condensates and high density quark matter

We consider here a Coulomb gauge quark model which includes an explicit construct for a nontrivial vacuum structure in QCD at finite density. Non-perturbative renormalization of ultraviolet diverges is performed by adding counterterms. The equation of state for u and d quark matter at zero temperature is calculated in the Hartree-Fock approximation.

Mesonic correlation functions at finite temperature in the NJL model

We employ the NJL model to calculate mesonic correlation functions at finite temperature and compare results with recent lattice QCD simulations. We employ an implicit regularization scheme to deal with the divergent amplitudes to obtain ambiguity-free, scale-invariant and symmetry-preserving physical amplitudes. Making the coupling constants of the model temperature dependent, we show that at low momenta our results agree qualitatively with lattice simulations.

Measurement of dijet azimuthal decorrelations at central rapidities in p(p)over-bar collisions at root s=1.96 TeV

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (p) over bar collisions at a center-of-mass energy root s=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

Can dissipation prevent explosive decomposition in high-energy heavy ion collisions?

We discuss the role of dissipation in the explosive spinodal decomposition scenario of hadron production during the chiral transition after a high-energy heavy ion collision. We use a Langevin description inspired by microscopic nonequilibrium field theory results to perform real-time lattice simulations of the behavior of the chiral fields. We show that the effect of dissipation can be dramatic. Analytic results for the short-time dynamics are also presented. (c) 2005 Elsevier B.V. All rights reserved.

Measurement of the shape of the boson rapidity distribution for p(p)over-bar -> Z/gamma(*)-> e(+)e(-)+X events produced at root s of 1.96 TeV

We present a measurement of the shape of the boson rapidity distribution for p (p) over bar -> Z/gamma(*)-> e(+)e(-)+X events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass 71 < M-ee < 111 GeV and uses 0.4 fb(-1) of data collected at the Fermilab Tevatron collider with the D0 detector. This measurement significantly reduces the uncertainties on the rapidity distribution in the forward region compared with previous measurements. Predictions of next-to-next-to-leading order (NNLO) QCD are found to agree well with the data over the full rapidity range.

Relativistic dynamics of Qqq systems

The bound state of constituent quarks forming a Qqq composite baryon is investigated in a QCD-inspired effective light-front model. The light-front Faddeev equations are derived and solved numerically. The masses of the spin 1/2 low-lying states of the nucleon, Lambda(0), Lambda(c)(+) and Lambda(b)(0), are found and compared to the experimental data. The data are qualitatively described with a flavor independent effective interaction.

Quark condensates and high density quark matter

We consider a Coulomb gauge quark model which includes an explicit construct for a nontrivial vacuum structure in QCD. The dynamics is described by a Hamiltonain that contains a linearly rising confining potential and longitudinal and transverse Coulomb-type interactions. The Coulomb potential gives rise to ultraviolate divergences which are non-perturbatively renormalized by adding appropriate counter terms to the Hamiltonian. The equation of state for u and d quark matter at zero temperature is derived in the Hartree-Fock approximation.