Spacelike and timelike pion electromagnetic form factor and Fock state components within the light-front dynamics

The simultaneous investigation of the pion electromagnetic form factor in the space- and timelike regions within a light-front model allows one to address the issue of nonvalence components of the pion and photon wave functions. Our relativistic approach is based on a microscopic vector-meson-dominance model for the dressed vertex where a photon decays in a quark-antiquark pair, and on a simple parametrization for the emission or absorption of a pion by a quark. The results show an excellent agreement in the space like region up to -10 (GeV/c)(2), while in timelike region the model produces reasonable results up to 10 (GeV/c)(2).

Finite-volume form factors in semi-classical approximation

A semi-classical approach is used to obtain Lorentz covariant expressions for the form factors between the kink states of a quantum field theory with degenerate vacua. Implemented on a cylinder geometry it provides an estimate of the spectral representation of correlation functions in a finite volume. Illustrative examples of the applicability of the method are provided by the sine-Gordon and the broken phi(4) theories in 1 + 1 dimensions. (C) 2003 Elsevier B.V. All rights reserved.

Qcd Sum Rules for the G(KK*pi)(Q(2)) form factor

The QCD Sum Rules have been used to evaluate the form factor in the vertex KK*pi. The method of QCD Sum Rules is based on the duality principle in which it is assumed that the hadrons can simultaneously be described in two levels: quarks and hadrons. This work showed that the, axial current, used to describe the meson K is not appropriated to study the form factor.

The kaon electromagnetic form factor in the light-front formalism

Numerical calculations are performed and compared to the experimental data for the electromagnetic form factor of the kaon, extracted from both components of the electromagnetic current, J(+) and J(-), with a pseudo-scalar coupling of the quarks to the kaon. In the case of J(+), there is no pair term contribution in the Drell-Yan frame (q(+) = 0). However, for J-, the pair term contribution is different from zero and is necessary in order to preserve the rotational symmetry of the current. The free parameters are the quark masses and the regulator mass.

Nonlinear Gravitational Waves: Their Form and Effects

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Functional Analysis for Gauge Fields on the Front-Form and the Light-Cone Gauge

Constrained systems in quantum field theories call for a careful study of diverse classes of constraints and consistency checks over their temporal evolution. Here we study the functional structure of the free electromagnetic and pure Yang-Mills fields on the front-form coordinates with the null-plane gauge condition. It is seen that in this framework, we can deal with strictu sensu physical fields.

Kaon and Pion Electromagnetic Form Factor Ratios in the Light-Front

We have applied the light-front formalism to calculate the electromagnetic form factors for the pion and the kaon from two models at low and high energies in order to explore the differences between such models. We have also compared the results for the ratio F(K)(Q(2))/F(pi)(Q(2)) with the experimental data, up to 10 [GeV/c](2) and we have observed that the theoretical results are in good concordance for low energies, but they are very different at higher energy scales.

Light-Front model of transition form-factors in heavy meson decay

Electroweak transition form factors of heavy meson decays are important ingredients in the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements from experimental data. In this work, within a. light-front framework, we calculate electroweak transition form factor for the semileptonic decay of D mesons into a pion or a kaon. The model results underestimate in both cases the new data of CLEO for the larger momentum transfers accessible in the experiment. We discuss possible reasons for that in order to improve the model.

Frame dependence of the pair contribution to the pion electromagnetic form factor in a light-front approach

The frame dependence of the pair-term contribution to the electromagnetic form factor of the pion is studied within the Light Front approach. A symmetric ansatz for the pion Bethe-Salpeter amplitude with a pseudo scalar coupling of the constituent to the pion field is used. In this model, the pair term vanishes for the Drell-Yan condition, while it is dominant for momentum transfer along the light-front direction.

Crystal Structure Determination of Mebendazole Form A Using High-Resolution Synchrotron X-Ray Powder Diffraction Data

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reversion by calcium of a yeast-like development to the original filamentous form, of the 10V10 5-fluorocytosine-sensitive mutant of Aspergillus niger

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desordens temporomandibulares e dor orofacial: estudo da qualidade de vida medida pelo Medical Outcomes Study 36 - Item Short Form Health Survey

JUSTIFICATIVA E OBJETIVOS: O conhecimento de indicadores de qualidade de vida (QV) relacionados à saúde bucal é especialmente relevante para a Odontologia considerando o impacto que as condições bucais podem provocar no bem estar psicológico e social. Estudos sobre aspectos psicossociais contribuem para maior integração da conduta clínica e assistencial, preocupação compartilhada com profissionais da saúde. Integrar as áreas de Psicologia e Odontologia quebrando paradigmas interdisciplinares e o interesse em conhecer os aspectos psicológicos dos pacientes, motivou a realização deste estudo. O objetivo deste estudo foi avaliar a QV dos pacientes com disfunção temporomandibular e/ou dor orofacial. MÉTODO: Foi aplicado o Questionário Genérico de Avaliação de Qualidade de Vida - Medical Outcomes Study 36 - Item Short Health Survey (SF-36) a 91 pacientes, que buscaram atendimento por apresentarem sinais e/ou sintomas de disfunção temporomandibular (DTM) e dor orofacial (DOF). O SF-36 avalia 8 domínios: capacidade funcional (CF), aspectos físicos (AF), dor, estado geral de saúde (EGS), saúde mental (SM), aspectos emocionais (AE), aspectos sociais (AS) e vitalidade (V). RESULTADOS: A análise estatística descritiva e inferencial pela Correlação de Pearson (p-valor < 0,05) demonstrou, com exceção da capacidade funcional (73,2), valores médios entre 50 e 64 para os demais domínios: AF - 57,6; Dor - 50; EGS - 54,5; V - 53,4; AS - 63,6; AE - 51,8; SM - 58. Considerando-se que a pontuação varia de 0 a 100, ou seja, do pior para o melhor estado de saúde, os valores médios foram baixos. Verificou-se correlação entre CF e EGS (p-valor 0,01), tendência de significância para dor e EGS (p-valor 0,07). CONCLUSÃO: Os aspectos dor e capacidade funcional interferem no estado geral de saúde; os pacientes com DTM e DOF sofreram impacto negativo na qualidade de vida pelo prejuízo dos aspectos físicos e mentais.

GHOST POLES IN THE NUCLEON PROPAGATOR - VERTEX CORRECTIONS AND FORM-FACTORS

Vertex corrections are taken into account in the Schwinger-Dyson equation for the nucleon propagator in a relativistic field theory of fermions and mesons. The usual Hartree-Fock approximation for the nucleon propagator is known to produce the appearance of complex (ghost) poles which violate basic theorems of quantum field theory. In a theory with vector mesons there are vertex corrections that produce a strongly damped vertex function in the ultraviolet. One set of such corrections is known as the Sudakov form factor in quantum electrodynamics. When the Sudakov form factor generated by massive neutral vector mesons is included in the Hartree-Fock approximation to the Schwinger-Dyson equation for the nucleon propagator, the ghost poles disappear and consistency with basic requirements of quantum field theory is recovered.

Effect of the bound nucleon form factors on charged-current neutrino-nucleus scattering

We study the effect of bound nucleon form factors on charged-current neutrino-nucleus scattering. The bound nucleon form factors of the vector and axial-vector currents are calculated in the quark-meson coupling model. We compute the inclusive C-12(nu(mu),mu(-))X cross sections using a relativistic Fermi gas model with the calculated bound nucleon form factors. The effect of the bound nucleon form factors for this reaction is a reduction of similar to8% for the total cross section, relative to that calculated with the free nucleon form factors.