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Register a new userDelta-baryon mass in a covariant Faddeev approach
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We present a calculation of the three-quark core contribution to the mass of the Delta-baryon in a Poincare-covariant Faddeev framework. A consistent setup for the dressed-quark propagator, the quark-quark and quark-diquark interactions is used, where all the ingredients are solutions of their respective Dyson-Schwinger or Bethe-Salpeter equations in rainbow-ladder truncation. We discuss the evolution of the Delta mass with the current-quark mass and compare to the previously obtained mass of the nucleon.
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We present a calculation of the three-quark core contribution to the mass of the Delta-baryon in a Poincare-covariant Faddeev framework. A consistent setup for the dressed-quark propagator, the quark-quark and quark-diquark interactions is used, where all the ingredients are solutions of their respective Dyson-Schwinger or Bethe-Salpeter equations in rainbow-ladder truncation. We discuss the evolution of the Delta mass with the current-quark mass and compare to the previously obtained mass of the nucleon.
An important ingredient of parton or string cascade models for ultrarelativistic heavy-ion reactions is a parton description of the baryon. Whereas previous models needed the concept of a diquark in an essential way, we have developed a new model using Diracs approach of Poincare-covariant many-body dynamics with constraints. In our model, the baryon is described as a dynamical set of three valence quarks and a fourth particle, the junction, which carries the momentum fraction of the sea quarks as well as all of the glue. The models parameters are the quark current masses, and one interaction strength, determined by the proton radius. Thus the model has no adjustable free parameters. Nevertheless, we obtain a remarkably good fit to the valence quark structure functions of the baryon
By solving the Faddeev equations we calculate the mass of the strange baryons in the framework of a relativistic constituent quark model. The Goldstone-boson-exchange quark-quark interaction is derived from $SU(3)_F$ symmetry, which is explicitly broken as the strange quark is much heavier. This broken symmetry can nicely be accounted for in the Faddeev framework.
We discuss a possible definition of the Faddeev-Popov matrix for the minimal linear covariant gauge on the lattice and present first results for the ghost propagator. We consider Yang-Mills theory in four space-time dimensions, for SU(2) and SU(3) gauge groups.
The covariant spectator formalism is used to model the nucleon and the $Delta$(1232) as a system of three constituent quarks with their own electromagnetic structure. The definition of the ``fixed-axis polarization states for the diquark emitted from the initial state vertex and absorbed into the final state vertex is discussed. The helicity sum over those states is evaluated and seen to be covariant. Using this approach, all four electromagnetic form factors of the nucleon, together with the {it magnetic} form factor, $G_M^*$, for the $gamma N to Delta$ transition, can be described using manifestly covariant nucleon and $Delta$ wave functions with {it zero} orbital angular momentum $L$, but a successful description of $G_M^*$ near $Q^2=0$ requires the addition of a pion cloud term not included in the class of valence quark models considered here. We also show that the pure $S$-wave model gives electric, $G_E^*$, and coulomb, $G^*_C$, transition form factors that are identically zero, showing that these form factors are sensitive to wave function components with $L>0$.
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