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Brazilian Journal of Physics, Volume: 34, Número: 1a, Publicado: 2004
  • Foreword

  • Strings in flat space and plane waves from N = 4 super Yang Mills

    Maldacena, Juan

    Resumo em Inglês:

    We explain how the string spectrum in flat space and plane waves arises from the large N limit of U(N) N = 4 super Yang Mills. We reproduce the spectrum by summing a subset of the planar Feynman diagrams. We also describe some other aspects of string propagation on plane wave backgrounds. This talk based on [1].
  • Gauge theories on the light-front

    Brodsky, Stanley J.

    Resumo em Inglês:

    The light-front quantization of gauge theories in light-cone gauge provides a frame-independent wavefunction representation of relativistic bound states, simple forms for current matrix elements, explicit unitary, and a trivial vacuum. The light-front Hamiltonian form of QCD provides an alternative to lattice gauge theory for the computation of nonperturbative quantities such as the hadronic spectrum and the corresponding eigenfunctions. In the case of the electroweak theory, spontaneous symmetry breaking is represented by the appearance of zero modes of the Higgs field. Light-front quantization then leads to an elegant ghost-free theory of massive gauge particles, automatically incorporating the Lorentz and 't Hooft conditions, as well as the Goldstone boson equivalence theorem.
  • Perspectives of the ALICE experiment

    Giubellino, Paolo

    Resumo em Inglês:

    The Large Hadron Collider, now under contruction at the European Center for Nuclear Research, represents a unique opportunity for Heavy-Ion Physics. It will provide nuclear collisions at a center-of-mass energy 30 times higher then the present Relativistic Heavy Ion Collider at BNL, currelty the highest energy nuclear accelerator. The LHC will open for this field a new era, in which particle production will be dominated by hard processes, and the energy densities will possibly be high enough to treat the generated quark-gluon plasma as an ideal gas. While RHIC is providing a wealth of interesting data, many physicists are working hard to prepare the experiments which will run at the LHC. ALICE, A Large Ion Collider Experiment, the dedicated detector designed to study nucleus-nucleus collisions at the LHC, is developing rapidly: the R&D is essentially complete, and large parts of the main detectors are in production. The scientific motivations and present status of Heavy Ion Physics, can be found in the review by T. Kodama [1]. In the following, I will summarize the experimental conditions at the LHC with nuclear beams, describe the main detector components of ALICE and briefly discuss the physics program of the experiment.
  • Elementary particles under the lens of the black holes

    Matsas, George E. A.

    Resumo em Inglês:

    After a brief review of the historical development and CLASSICAL properties of the BLACK HOLES, we discuss how our present knowledge of some of their QUANTUM properties shed light on the very concept of ELEMENTARY PARTICLE. As an illustration, we discuss in this context the decay of accelerated protons, which may be also relevant to astrophysics.
  • Collider tests for neutrino mass generation in a supersymmetric world with R-parity violation

    Magro, M. B.

    Resumo em Inglês:

    We summarize the low energy features of a supersymmetric class of models with bilinear R-parity violation. We analyze two cases where the supersymmetry breaking is mediated either by supergravity or by anomaly induced contributions to the soft parameters and compare both scenarios in the context of recent neutrino conversion data and collider physics. We show that both classes of models have a large potential to discoveries in collider experiments as well as in neutrino experiments.
  • Topological mass generation and duality transformations in diverse dimensions

    Wotzasek, Clovis

    Resumo em Inglês:

    In this seminar we shall discuss the issue of duality transformation in the context of f topological mass generation in diverse dimensions. Particular emphasis will be given to the mass generation mechanism as the result of interference between self and anti self-dual components, as disclosed by the soldering formalism. Since this is a gauge embedding procedure derived from an old algorithm of second-class constraint conversion used by the author to approach anomalous gauge theories, a quick review of the subject will be presented. The problem of classification of the electromagnetic duality groups that is closely related will also be briefly discussed. Particular emphasis will be given to a new approach to duality based on the soldering embedding to tackle to problem of mass generation by topological mechanisms in D=3 and D=4 dimensions including the couplings to dynamical matter and nonlinear cases.
  • Quark-lepton nonuniversality

    Xiao-Yuan, Li; Ma, Ernest

    Resumo em Inglês:

    There is new experimental evidence which may be interpreted as a small departure from quark-lepton universality. We propose to understand this as the result of a hierarchy of mass scales in analogy to m u, m d << L QCD for strong isospin. We show <img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a08img01.gif" align=absbottom>< <img id="_x0000_i1027" src="../../img/revistas/bjp/v34n1a/a08img02.gif" align=absbottom>< <img id="_x0000_i1028" src="../../img/revistas/bjp/v34n1a/a08img03.gif" align=absbottom>< <img id="_x0000_i1029" src="../../img/revistas/bjp/v34n1a/a08img04.gif" align=absbottom>in principle, but all are still approximately equal. New physics is predicted at the TeV scale.
  • Alternative dark energy models: an overview

    Lima, J. A. S.

    Resumo em Inglês:

    A large number of recent observational data strongly suggest that we live in a flat, accelerating Universe composed of ~ 1/3 of matter (baryonic + dark) and ~ 2/3 of an exotic component with large negative pressure, usually named Dark Energy or Quintessence. The basic set of experiments includes: observations from SNe Ia, CMB anisotropies, large scale structure, X-ray data from galaxy clusters, age estimates of globular clusters and old high redshift galaxies (OHRG's). It is now widely believed that such results provide the remaining piece of information connecting the inflationary flatness prediction (W T = 1) with astronomical observations. From a theoretical viewpoint, they have also stimulated the current interest for more general models containing an extra component describing this unknown dark energy, and simultaneously accounting for the present accelerating stage of the Universe. In this review we present a simplified picture of the main results and discuss briefly some difficulties underlying the emerging dark energy paradigm.
  • Light quark spectroscopy and charm decays

    Reis, Alberto

    Resumo em Inglês:

    The connection between light quark spectroscopy and hadronic decays of D mesons is discussed, with emphasis on the physics of the light scalar mesons. Recent results from charm decays are presented.
  • Hunt for the quark-gluon plasma: 20 years later

    Kodama, Takeshi

    Resumo em Inglês:

    We review briefly the recent progress in the search for the quark-gluon plasma (QGP) at CERN SPS and BNL RHIC. Several model analyses and observables, such as hadronic thermal equilibrium, hydrodynamical flow, HBT, jet quenching, etc. which lead to the present conception of the formation of QGP are described.
  • Experimental status of corrections to Newton's gravitational law inspired by extra dimensional physics

    Mostepanenko, V. M.

    Resumo em Inglês:

    Corrections to Newton's gravitational law inspired by extra dimensional physics and by the exchange of light and massless elementary particles between the atoms of two macrobodies are considered. These corrections can be described by the potentials of Yukawa-type and by the power-type potentials with different powers. The strongest up to date constraints on the corrections to Newton's gravitational law are reviewed following from the Eötvos- and Cavendish-type experiments and also from the measurements of the Casimir and van derWaals force.
  • Preliminary results from DØ run II data

    Carvalho, Wagner de Paula

    Resumo em Inglês:

    We present recent physics results from the data collected by the DØ detector in this early stage of Run II of the Tevatron proton-antiproton collider. Emphasis is given to the Forward Proton Detector, a new subsystem that will enable detailed studies of diffractive phenomena at Tevatron.
  • Summary talk: quantum field theory

    Carvalho, C. A. A. de

    Resumo em Inglês:

    We present a summary of the contributions to Quantum Field Theory of the XXIII Brazilian National Meeting on Particles and Fields.
  • XV Workshop on Hadron Interactions: Retinha XV

  • QCD glueball sum rules revisited

    Forkel, Hilmar

    Resumo em Inglês:

    We discuss several key problems of conventional QCD glueball sum rules in the spin-0 channels and show how they are overcome by nonperturbative Wilson coefficients. The nonperturbative contributions originate from direct instantons and, in the pseudoscalar channel, additionally from topological charge screening. The treatment of the direct-instanton sector is based on realistic instanton size distributions and renormalization at the operator scale. The resulting predictions for spin-0 glueball properties as well as their implications for experimental glueball searches are discussed.
  • The flavor asymmetry in the polarized proton sea

    Steffens, F. M.

    Resumo em Inglês:

    We perform a careful study on the effect of the Pauli blocking to the light polarized antiquark structure of the proton sea. We develop the formal expressions for the polarized antiquark distributions, highlighting the role played by quark statistics and the vacuum structure. The ratio involving the polarized antiquarks is calculated. In particular, it is found that D<img id="_x0000_i1026" src="../../../../img/revistas/bjp/v34n1a/a17img01.gif" align=absbottom>(x)/D<img id="_x0000_i1027" src="../../../../img/revistas/bjp/v34n1a/a17img02.gif" align=absbottom>(x) should be negative and x independent.
  • The J/psiDD* vertex

    Rodrigues da Silva, R.; Matheus, R.D.; Navarra, F.S.; Nielsen, M.

    Resumo em Inglês:

    We employ QCD sum rules to calculate the J/psiDD* form factors and coupling constant by studying the threepoint J/psiD*D correlation function. We find that the momentum dependence of the form factor depends on the off-shell meson. We get a value for the coupling which is in agreement with estimates based on constituent quark model.
  • J/psiD*D* form factor from QCD sum rules

    Bracco, M.E.; Chiapparini, M.; Navarra, F.S.; Nielsen, M.

    Resumo em Inglês:

    We calculate the J/psiD*D* form factor and coupling constant from QCD Sum Rules in the cases where J/psi and D* mesons are off-shell. The results show that this method is consistent and allows to extract the same coupling constant for the vertex.
  • Pion mass dependence of nucleon magnetic moments

    Braghin, F. L.

    Resumo em Inglês:

    The relevance of the pion mass, provenient from a term which explicitely breaks chiral symmetry in the Lagrangian, for nucleon magnetic moment in the frame work of the Skyrme model in two different versions: the usual one model and a modified one which includes a coupling to a light scalar meson field, the sigma s(<img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a08img11.gif" align=absmiddle> 500 - 600 MeV). Results are compared to other calculations. Our main motivation comes from usual extrapolations for values of low energy QCD observables obtained in lattices with large values of pion/quark masses toward realistic value of m p which do not allow it. We do a comparison with results from the Cloudy Bag Model and a chiral hadronic model from chiral perturbation theory. There are several resulting extrapolations from the region of large pion mass to the realistic value depending on the considered model for low energy QCD.
  • Percolation of Monte Carlo clusters

    Wanzeller, W.G.; Cucchieri, A.; Mendes, T.; Krein, G.

    Resumo em Inglês:

    Percolation theory is of interest in problems of phase transitions in condensed matter physics, and in biology and chemistry. More recently, concepts of percolation theory have been invoked in studies of color deconfinement at high temperatures in Quantum Chromodynamics. In the present paper we briefly review the basic concept of percolation theory, exemplify its application to the Ising model, and present the arguments for a possible relevance of percolation theory to the problem of color deconfinement.
  • Impact of the recent Jefferson lab data on the structure of the nucleon

    Araújo, W.R.B. de; Frederico, T.; Beyer, M.; Weber, H.J.

    Resumo em Inglês:

    The simultaneous fit of proton ratio m pG Ep/G Mp, qF2p/F1p to the recent experimental data and static properties of the nucleon is studied within a light-front model with different spin coupling schemes and wave functions. The position of the zero of proton electric form factor is sensitive to the presence of a hard constituent quark component in the nucleon wave function. The fitting of the new data for the ratios is achieved with a hard momentum scale about 4-5 GeV.
  • The pion electromagnetic form factor in the meson cloud model

    Carvalho, F.; Durães, F.O.; Navarra, F.S.; Nielsen, M.

    Resumo em Inglês:

    In this work we calculate the meson cloud effects on the pion electromagnetic form factor and perform a comparison with experimental data. We show that, even though the cloud is not the only non-perturbative process to be considered, its contribution is significant. We also study the influence of the cutoff choices on the results.
  • Phase-shift definition for pion-nucleon scattering from chiral perturbation theory

    Cavalcante, Isabela P.; Borges, J. Sá

    Resumo em Inglês:

    Chiral Perturbation Theory is considered as a very precise method when applied to pion-nucleon scattering near threshold and in the unphysical region since in these cases the pion momenta are small. In this framework, third order calculation yields a non-relativistic scattering amplitude with nine free parameters. From the fact that the resulting partial-wave amplitudes do not respect elastic unitarity relation, one has that the phase-shift definition is ambiguous. In this article, we present the comparison of the model with experimental data for two different phase-shift formulas and we conclude that the results are very sensitive to phase-shift definition.
  • Correlations between total cross sections and slopes

    Martini, A. F.; Menon, M. J.; Montanha, J.

    Resumo em Inglês:

    We investigate correlations between the total cross section and the slope of the elastic differential cross section for proton-proton and antiproton-proton scattering at the highest energies. Based on the empirical behavior of these quantities as function of the energy, we select two different analytical parametrizations connecting them, and obtain the correlations through fits to the experimental data available. We present and discuss practical uses of extrapolations and interpolations of the results. In the former case we refer to the estimation of the proton-proton total cross sections from the proton-air cross sections (obtained from cosmic-ray experiments), and in the later case, we critically discuss the recent measurement of the slope parameter at the BNL RHIC at 200 GeV by the pp2pp Collaboration.
  • Extensions of the extrema bounds for the pomeron intercept to meson-proton, gamma-proton and gamma-gamma scattering

    Luna, E. G. S.; Menon, M. J.; Montanha, J.

    Resumo em Inglês:

    Making use of the extrema bounds for the soft pomeron intercept, recently determined by fits to pp and <img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a25img08.gif" align=absbottom>data (from both accelerator and cosmic-ray experiments), we investigate the total cross sections for pion-proton, kaon-proton, gamma-proton and gamma-gamma scattering. We show that by means of global fits, the extrema bounds are in agreement with the bulk of experimental data presently available, and that extrapolations to higher energies indicate different behaviors for the rise of the total cross sections. We also discuss factorization and quark counting, showing that both bounds are in agreement with these properties.
  • A model for J/psi - kaon cross section

    Azevedo, R.S.; Nielsen, M.

    Resumo em Inglês:

    We calculate the cross section for the dissociation of J/psi by kaons within the framework of a meson exchange model. We find that, depending on the values of the coupling constants used, the cross section can vary from 5 mb to 30 mb at <img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a11img03.gif" align=absbottom>~ 5 GeV.
  • A semi-classical picture of the charmonium-hadron interaction

    Fogaça, D.A.; Kugeratski, M.S.; Navarra, F.S.

    Resumo em Inglês:

    In this work, we present calculations for the charmonium-hadron cross section. The hadron is represented by an external color field and the charmonium is represented by a small color dipole. Using high-energy approximations we compute the relevant cross sections, which agree with results obtained with other methods.
  • Hadron-hadron interactions in Coulomb gauge QCD

    Szpigel, Sérgio; Krein, G.; Marques de Carvalho, R. S.

    Resumo em Inglês:

    We describe the derivation of an effective Hamiltonian which involves explicit hadron degrees of freedom and consistently combines chiral symmetry and color confinement. We use a method known as Fock-Tani (FT) representation and a quark model formulated in the context of Coulomb gauge QCD. Using this Hamiltonian, we evaluate the dissociation cross section of J/psi in collision with rho.
  • Antihyperon polarization in inclusive processes at high energies

    Barros, Jr., C. C.; Hama, Y.

    Resumo em Inglês:

    We propose a model that we believe is the main source of the antihyperon polarization in high-energy protonnucleus inclusive reactions. The polarization is originated by the final-state interactions between the antihyperons and other produced particles in these collisions (predominantly pions). The model is based on two elements: the low-energy pion-hyperon interaction (described by chiral effective Lagrangians) and the statistical fluctuations plus expansion of the background matter.
  • Can we observe the radion and Higgs signals in peripheral heavy ion collisions?

    Roldão, C. G.; Lietti, S. M.

    Resumo em Inglês:

    We investigate the sensitivity of the heavy ion mode of the LHC to Higgs boson and Radion production via photon-photon fusion through the analysis of the processes <FONT FACE=Symbol>gg</FONT> -> <FONT FACE=Symbol>gg</FONT>, <FONT FACE=Symbol>gg</FONT> -> <img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a08img09.gif" align=absmiddle>, and <FONT FACE=Symbol>gg ® gg</FONT>in peripheral heavy ion collisions. We suggest cuts to improve the Higgs and Radion signal over standard model background ratio and determine the capability of LHC to detect these particles production.
  • On open charm production in heavy ion collisions

    Durães, F.O.; Navarra, F.S.; Nielsen, M.

    Resumo em Inglês:

    We update the calculation of c - <img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a19img02.gif" align=absbottom>production in the initial stage of nucleus - nucleus collisions and within quark gluon plasma, using the most recent and most accepted values for the ingredients, such as nuclear parton distributions, quark masses, couplings and fireball parameters. We find a large discrepancy in the charm yields, depending on the input choices. A global analysis of all the different cases suggests that the “in-plasma” production is a significant fraction of the total yield.
  • The nuclear pseudospin symmetry along an isotopic chain

    Lisboa, R.; Malheiro, M.; Alberto, P.

    Resumo em Inglês:

    We investigate the isospin dependence of pseudospin symmetry in the chain of tin isotopes (from 120Sn until 170Sn). Using a Woods-Saxon parametrization of the nuclear potential for these isotopes we study in detail the effect of the vector-isovector rho and Coulomb potentials in the energy splittings of neutron and proton pseudospin partners in the isotopic chain. We conclude that the realization of nuclear pseudospin symmetry does not change considerably with the mass number, and is always favored for neutrons. We also find that the rho potential accounts for essentially all the pseudospin isospin asymmetry observed and that the Coulomb potential plays a negligible role in this asymmetry. This can be explained by the dynamical nature of pseudospin symmetry in nuclei, namely the dependence of the pseudospin splittings on the shape of the nuclear mean-field potential.
  • Weak decay constant of pseudoscalar mesons in a QCD-inspired model

    Salcedo, L. A. M.; Melo, J.P.B.C. de; Hadjmichef, D.; Frederico, T.

    Resumo em Inglês:

    We show that a linear scaling between the weak decay constants of pseudoscalars and the vector meson masses is supported by the available experimental data. The decay constants scale as f m/f p = MV/Mr (f m decay constant and M V vector meson ground state mass). This simple form is justified within a renormalized lightfront QCD-inspired model for quark-antiquark bound states.
  • High-pT results from the STAR experiment at RHIC

    Suaide, A.A.P.

    Resumo em Inglês:

    High-pT measurements in relativistic heavy ion collisions provide a unique set of tools to investigate the early stages of the collision. In this paper we report the high-pT measurements of inclusive hadron spectra, azimuthal anisotropies and two particle correlations performed by the STAR detector for 200 GeV Au+Au, p+p and d+Au collisions at RHIC. The results suggest that the phenomena observed uniquely in central Au+Au collisions are due to strong final state interactions in the hot and dense medium created in such collisions.
  • Strangeness production in relativistic heavy ion collisions

    Munhoz, M. G.

    Resumo em Inglês:

    In this article, I'll present some of the motivations for the study of strangeness production in relativistic heavy ions collisions. Several experimental results have demonstrated that strangeness production is a powerful tool to investigate new phenomena in these collisions. Perspectives are still opened for new and exciting results in these studies.
  • Spinodal instability in the quark-gluon plasma

    Aguiar, C. E.; Fraga, E. S.; Kodama, T.

    Resumo em Inglês:

    We investigate the onset of spinodal decomposition in a relativistic fluid of quarks coupled to a nonequilibrium chiral condensate. Studying small fluctuations around equilibrium, we identify the role played by sound and chiral waves in the generation of unstable modes.
  • Charged polytropic compact stars

    Ray, Subharthi; Malheiro, Manuel; Lemos, José P. S.; Zanchin, Vilson T.

    Resumo em Inglês:

    In this work, we analyze the effect of charge in compact stars considering the limit of the maximum amount of charge they can hold. We find that the global balance of the forces allows a huge charge (~ 10(20) Coulomb) to be present in a neutron star producing a very high electric field (~ 10(21) V/m). We have studied the particular case of a polytropic equation of state and assumed that the charge distribution is proportional to the mass density. The charged stars have large mass and radius as we should expect due to the effect of the repulsive Coulomb force with the M/R ratio increasing with charge. In the limit of the maximum charge the mass goes up to ~ 10 <img id="_x0000_i1026" src="../../img/revistas/bjp/v34n1a/a38img08.gif" align=absbottom>which is much higher than the maximum mass allowed for a neutral compact star. However, the local effect of the forces experienced by a single charged particle, makes it to discharge quickly. This creates a global force imbalance and the system collapses to a charged black hole.
  • Finite-size constraints on nucleation of hadrons in a quark-gluon plasma

    Fraga, Eduardo S.; Venugopalan, Raju

    Resumo em Inglês:

    We discuss finite-size effects on homogeneous nucleation in first-order phase transitions. We study their implications for cosmological phase transitions and to the hadronization of a quark-gluon plasma generated in high-energy heavy ion collisions.
  • Comparison between classification using impact parameter and using number of participants in relativistic nuclear collisions

    Aguiar, C.E.; Andrade, R.; Grassi, F.; Hama, Y.; Kodama, T.; Osada, T.; Socolowski Jr., O.

    Resumo em Inglês:

    Using the hydrodynamical code NeXSPheRIO, we compare predictions as usually done in hydrodynamics, using centrality windows defined through the impact parameter, and as obtainable experimentally, using windows in participant number.
  • Incident-energy dependence of the effective temperature in heavy-ion collisions

    Gazdzicki, M.; Gorenstein, M. I.; Grassi, F.; Hama, Y.; Kodama, T.; Socolowski Jr., O.

    Resumo em Inglês:

    We study, in a hydrodynamical approach, the energy dependence of the kaon mT spectra in central Pb+Pb (Au+Au) collisions. We show that the experimental data of the inverse slope parameter can be reproduced with a reasonable choice of both energy-dependent freeze-out temperature and initial conditions.
  • Particle ratio fluctuations and isobaric ensemble for chemical freeze-out scenario

    Portugal, Licinio L. S.

    Resumo em Inglês:

    In this work, we study the behavior of event-by-event distribution of particle ratios in Gran Canonical and Isobaric ensemble.We show that the experimental value of the width in the K/p ratio distribution is much wider than that given by a unique grand canonical ensemble or Isobaric ensembe and maybe a mixture is required.
  • The effects of conserved charges in a nuclear equation of state

    Tavares, B. Mattos

    Resumo em Inglês:

    We report the present status on the construction of an equation of state (EoS) for the strongly interacting matter which is to be used in the hydrodynamical calculations for the ultra-relativistic heavy ion collisions. In the present version, the conservation of isospin, baryon number and strangeness are taken into account. A preliminary hydrodynamical result for our EoS, using the hydro code SPHERIO, is also shown.
  • Erratum

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