Relativistic quark model for theΩ−electromagnetic form factors

Abstract

We compute the Ω − electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Ω − electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.

γ*N→N*(1520) form factors in the timelike regime

“…After this internal momentum integration, in the process of the covariant integration over the global momentum of the interacting diquark one may keep only the main contribution, which is originated by the onmass-shell pole of the diquark -while the remaining quark that interacts with the photon is taken to be offmass-shell [25]. This last integration on the on-shell diquark internal momenta amounts to having the qqq system as a quark-diquark system, and to treating the diquark with an effective average mass m D [21,25,26]. It is also an ingredient of the model that the electromagnetic quark current is represented by a parametrization of vector meson dominance [21,26,34,35].…”

“…This last integration on the on-shell diquark internal momenta amounts to having the qqq system as a quark-diquark system, and to treating the diquark with an effective average mass m D [21,25,26]. It is also an ingredient of the model that the electromagnetic quark current is represented by a parametrization of vector meson dominance [21,26,34,35]. In addition to the contributions from the core of valence quarks, the covariant spectator quark model can include also a covariant parametrization of the meson cloud effects that are important in the low momentum transfer region and that depend on the baryons participating in the reaction [6,7,22,23,31,[36][37][38].…”

“…In the covariant spectator quark model, the application of impulse approximation to the interaction of a photon with a baryon, seen as a three quark qqq state, justifies that one integrates out the relative internal momentum in the spectator diquark subsystem [21,25,26]. After this internal momentum integration, in the process of the covariant integration over the global momentum of the interacting diquark one may keep only the main contribution, which is originated by the onmass-shell pole of the diquark -while the remaining quark that interacts with the photon is taken to be offmass-shell [25].…”

“…In the covariant spectator quark model the baryon wave functions are specified by the flavor, spin, orbital angular momentum and radial excitations of the quarkdiquark states that are consistent with the baryon quantum number [8,21,26,36]. The nucleon wave function Ψ N was obtained in Ref.…”

“…This model is based on the covariant spectator theory (CST) [19]. In a relatively successful and unifying way, our approach pictures a large variety of baryons as a superposition of a core of three valence quarks and meson cloud components [6][7][8][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. After a series of applications of the model to the electromagnetic excitation of baryons in the spacelike regime, we analyzed also the impact of the ∆(1232) resonance in the timelike reactions [6,7].…”