Poincaré-Covariant Quark Models of Baryon Form Factors

Coester, F.; Riska, D.O.

doi:10.1007/s006010050092

Cited by 19 publications

(19 citation statements)

References 17 publications

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“…Some studies along these lines have been made [44,45] but they did not go quite far, due perhaps to the related nonlinear constraint between the coordinates, x 0 and x. In practice, recent applications of the pointform approach [11,12,23,24,46,47] rely on employing wave functions issued from a mass operator whose solutions can also be identified with instant-form ones in the center of mass system. These last solutions are characterized by the description of the dynamics on a hyper-plane, λ 0 · x = ct, with λ µ 0 = (1, 0, 0, 0).…”

Section: Improved Interactionmentioning

confidence: 99%

Comparison of form factors calculated with different expressions for the boost transformation

2003

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The effect of different boost expressions is considered for the calculation of the ground-state form factor of a two-body system made of scalar particles interacting via the exchange of a scalar boson. The aim is to provide an uncertainty range on methods employed in implementing these effects as well as an insight on their relevance when an "exact" calculation is possible. Using a wave function corresponding to a mass operator that has the appropriate properties to construct the generators of the Poincaré algebra in the framework of relativistic quantum mechanics, form factors are calculated using the boost transformations pertinent to the instant, front and point forms of this approach. Moderately and strongly bound systems are considered with masses of the exchanged boson taken as zero, 0.15 times the constituent mass m, and infinity. In the first and last cases, a comparison with "exact" calculations is made (Wick-Cutkosky model and Feynman triangle diagram). Results with a Galilean boost are also given. Momentum transfers up to Q 2 = 100 m 2 are considered. Emphasis is put on the contribution of the single-particle current, as usually done. It is found that the present point-form calculations of form factors strongly deviate from all the other ones, requiring large contributions from two-body currents. Different implementations of the point-form approach, where the role of these two-body currents would be less important, are sketched.

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Section: Improved Interactionmentioning

confidence: 99%

Comparison of form factors calculated with different expressions for the boost transformation

2003

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“…The construction of unitary representations of the Poincaré group sketched here naturally leads to point-form kinematics. Once the eigenfunctions of the mass operator are known, it is easy to realize unitary transformations to other forms of kinematics explicitly [2]. Let Ψ n (v, κ, k) be eigenfunctions of M, with eigenvalues M n .…”

Section: The Hilbert Space Of 3-quark Statesmentioning

confidence: 99%

Covariant quark model for the baryons

Coester¹,

Dannbom²,

Riska³

1998

Nuclear Physics A

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A family of simply solvable covariant quark models for the baryons is presented. With optimal parameter choices the models reproduce the empirical spectra of the baryons in all flavor sectors to an accuracy of a few percent. Complete spectra are obtained for all states of the strange, charm and beauty hyperons with L ≤ 2. The magnetic moments and axial coupling constants of the ground state baryons correspond to those of conventional quark models. We construct current-density operators that are consistent with empirical nucleon form factors at low and medium energies. 0

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“…The latter depend on the Hamiltonian model for the 3-quark system. We here employ a simple covariant harmonic oscillator model based on linear confining interaction with a flavor-spin dependent hyperfine interaction, which describes the empirical spectrum very well [15].…”

Section: Introductionmentioning

confidence: 99%

Nucleon resonance transition couplings to vector mesons

2001

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Recent heavy ion experiments indicate modifications of the ρ−meson mass in medium. In the CERES experiments ρ−mesons are produced at ∼ normal nuclear matter density, where hadrons are more appropriate constituents than quarks. A collective "nuclear ρ", in which every nucleon is excited to the N (1520) state, with equal amplitude, enters in this description. At the higher densities reached by future experiments constituent quarks become the appropriate variables. Here the ρ and ω transition couplings to the nucleon resonances up to 1700 MeV, including the N (1520), are derived by means of the chiral quark model. The relevant coupling constants are expressed in terms of the corresponding vector coupling constants to nucleons. The quality of the model relations is tested by a calculation of the corresponding pion-resonance coupling constants, which are known from the empirical pion decay widths.

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Poincaré-Covariant Quark Models of Baryon Form Factors

Cited by 19 publications

References 17 publications

Comparison of form factors calculated with different expressions for the boost transformation

Comparison of form factors calculated with different expressions for the boost transformation

Covariant quark model for the baryons

Nucleon resonance transition couplings to vector mesons

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