arXiv subjects

Felix Schlumpf

Publications and source records attributed to Felix Schlumpf.

12 recordsLinked to original sources

arXiv1995

RELATIVISTIC CORRECTIONS TO THE ELECTROMAGNETIC AND AXIAL MOMENTS OF NUCLEI AND OTHER COMPOSITE SYSTEMS

We calculate the electromagnetic and axial nuclear moments of the deuteron and triton as a function of their radius using a relativistic two-nucleon and three-nucleon model formulated on the light-cone. The results also provide an estimate of the nuclear binding corrections to helicity-dependent deep inelastic scattering sum rules. At large nucleon radius, the moments are given by the usual non-relativistic formulae modified by finite binding effects. At small radius, the moments take the canonical values given by the generalization of the Drell-Hearn-Gerasimov sum rule. In addition, as R-->0, the constituent helicities become completely disoriented, and the Gamow-Teller matrix element vanishes. Thus, in the pointlike limit MR-->0, the moments of a spin-one bound states coincide with the canonical couplings of elementary spin-one bosons of the Standard Model, mu=e/M, Q=-e/M^2, and g_A=0.

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arXiv1994

The Impact of QCD and Light-Cone Quantum Mechanics on Nuclear Physics

We discuss a number of novel applications of Quantum Chromodynamics to nuclear structure and dynamics, such as the reduced amplitude formalism for exclusive nuclear amplitudes. We particularly emphasize the importance of light-cone Hamiltonian and Fock State methods as a tool for describing the wavefunctions of composite relativistic many-body systems and their interactions. We also show that the use of covariant kinematics leads to nontrivial corrections to the standard formulae for the axial, magnetic, and quadrupole moments of nucleons and nuclei.

hep-ph↗

arXiv1994

Beta decay of hyperons in a relativistic quark model

A relativistic constituent quark model is used to calculate the semileptonic beta decay of nucleons and hyperons. The parameters of the model, namely, the constituent quark mass and the confinement scale, are fixed by a previous calculation of the magnetic moments of the baryon octet within the same model. We discuss the momentum dependence of the form factors, possible configuration mixing and SU(3) symmetry breaking. We conclude that the relativistic constituent quark model is a good framework to analyze electroweak properties of the baryons.

hep-ph↗

arXiv1994

Charge form factors of pseudoscalar mesons

The elastic charge form factors of the pion, kaon, D- and B-mesons are calculated within a relativistic constituent quark model formulated on the light-cone. Our parameter free predictions agree well with the available data. The results are approximately independent of the assumed form of the light-cone wave function, in particular they do not depend on the high momentum tail of the wave function for energies accessible to present experiments.

hep-ph↗

arXiv1994

The Form Factors of the Nucleons

We demonstrate that a relativistic constituent quark model can give nucleon form factors that agree well with recent, accurate measurements. The relativistic features of the model and the specific form of the wave function are essential for the result. (Talk given at 14th International Conference on Few-Body Problems in Physics, Williamsburg, Virginia, USA, May 26-31, 1994)

hep-ph↗

arXiv1994

Wavefunction-Independent Relations between the Nucleon Axial-Coupling g_A and the Nucleon Magnetic Moments

We calculate the proton's magnetic moment $μ_p$ and its axial-vector coupling $g_A$ as a function of its Dirac radius $R_1$ using a relativisitic three-quark model formulated on the light-cone. The relationship between $μ_p$ and $g_A$ is found to be independent of the assumed form of the light-cone wavefunction. At the physical radius $R_1=0.76$ fm, one obtains the experimental values for both $μ_p$ and $g_A$, and the helicity carried by the valence $u$ and $d$ quarks are each reduced by a factor $\simeq 0.75$ relative to their non-relativistic values. At large proton radius, $μ_p$ and $g_A$ are given by the usual non-relativistic formulae. At small radius, $μ_p$ becomes equal to the Dirac moment, as demanded by the Drell-Hearn-Gerasimov sum rule. In addition, as $R_1 \to 0,$ the constituent quark helicities become completely disoriented and $g_A \to 0$.

hep-ph↗

arXiv1993

A Relativistic Constituent Quark Model

We investigate the predictive power of a relativistic quark model formulated on the light-front. The nucleon electromagnetic form factors, the semileptonic weak decays of the hyperons and the magnetic moments of both baryon octet and decuplet are calculated and found to be in excellent agreement with experiment.

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arXiv1993

Magnetic Moments of the Baryon Decuplet in a Relativistic Quark Model

The magnetic moments of the baryon decuplet are calculated in a relativistic constituent quark model using the light-front formalism. Of particular interest are the magnetic moments of the $Ω^-$ and $Δ^{++}$ for which new recent experimental measurements are available. Our calculation for the magnetic moment ratio $μ(Δ^{++})/μ(p)$ is in excellent agreement with the experimental ratio, while our ratio $μ(Ω^-)/μ(Λ^0)$ is slightly higher than the experimental ratio.

hep-ph↗

arXiv1993

The Electric and Magnetic Form Factors of the Neutron

We derive the electric and magnetic form factors of the neutron in the framework of a relativistic constituent quark model. Our parameter free prediction agrees well with a recent, accurate measurement. The relativistic features of the model and the specific form of the wave function are essential for the result. Comparisons are made to other models based on VMD, PQCD and QCD sum rules.

hep-ph↗

arXiv1993

Nucleon Form Factors in a Relativistic Quark Model

We demonstrate that a relativistic constituent-quark model can give nucleon form factors in agreement with data for both low and high momentum transfer. The relativistic features of the model and the specific form of the wave function are essential for the result.

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arXiv1992

Relativistic Constituent Quark Model of Electroweak Properties of Baryons

We calculate the electroweak properties of nucleons and hyperons in a relativistic constituent quark model using the light-front formalism. The parameters of the model, namely the constituent quark mass and the confinement scale, can be uniquely chosen for both the electromagnetic and weak experimental data. A consistent physical picture of the $qqq$ system appears in this work with a symmetric nucleon wave function and an asymmetric hyperon wave function. Only for the strangeness-changing weak decays do we need nontrivial form factors of the constituent quark.

hep-ph↗

arXiv1992

Relativistic Constituent Quark Model for Baryons

The electroweak properties of nucleons and hyperons are calculated in a relativistic constituent quark model. The baryons are treated as three quark bound states, and the diagrams of perturbation theory are considered on the light front. The electroweak properties of the baryons are of nonperturbative nature and can be represented by one-loop diagrams. We consider different extensions of the simplest model: quark form factors, configuration mixing of the wave function, asymmetric wave function, wave function different from the one of a harmonic oscillator valid up to energies of more than 30 GeV$^2$. A comprehensive study of various baryonic properties is given: elastic form factors of the nucleon, magnetic moments of the baryon octet, semileptonic weak form factors. This analysis also gives the Kobayashi-Maskawa matrix element $V_{us}$ and a sound symmetry breaking scheme for the Cabibbo theory. A consistent physical picture appears in this work. The nucleon consists of an unmixed, symmetric three quark state, the wave function of the hyperons is however asymmetric with a spin-isospin-0 diquark. Only for the strangeness-changing weak decay do we need nontrivial form factors.

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