Baryon resonances as bound (q)3-states coupled to meson fields

Abstract

Dedicated to Professor Theo Mayer-Kuckuk on the occasion of his 60th birthdayWithin the framework of the non-relativistic quark model (NRQM) we discuss the influence of the coupling between baryonic excitations and meson fields. This leads to the interpretation of the baryon resonances as bound (q)3-configurations embedded in the corresponding meson-baryon continua. This concept is formulated analytically and applied to the description of the low-lying (N = 0)-and (N = 1)-multiplets with strangeness (S=0) and (S=-1). It turns out that the effects of this coupling are comparable in size to the effects induced by the hypcrfine interaction. In particular, a remarkable cancellation of the spin-orbit forces of the qq-interaction and the meson-baryon interaction is observed. The implications of the strong baryon-meson coupling on the baryon-baryon interaction and on the formulation of the Hamiltonian for a multibaryon system are briefly discussed.

Bottomonia: open bottom strong decays and spectrum

“…[15,16]) is very successful in reproducing the behavior of observables such as the spectrum and the magnetic moments, but it neglects pair-creation effects. These effects give rise to virtual qq − qq (qqq − qq) components in the hadron wave function and shifts of the physical mass with respect to the bare mass [17], as already shown by several authors in the baryon [18][19][20][21][22] and meson [23][24][25][26][27][28][29][30][31][32][33][34][35][36] sectors. Some example are the resonance Λ(1405), that decays into Σπ, but it is strongly influenced by the nearbyKN channel [37], and the f 0 (980), that decays into ππ, but behaves remarkably as a KK molecule [38].…”

Quark Model Calculations of the N to Delta Reaction

“…However, an explicit manifestation of quark pair and/or meson effects should be looked for in the baryon widths. A work on these lines has been done some time ago: the IK model has been extended introducing a direct quarkmeson coupling by means of appropriate interaction lagrangians and used for the description of both masses and widths of baryons [69]. The elastic nucleon form factors provide another example of physical quantities for which such effects are expected to be relevant.…”

TheX(3872) as a charmonium state plus an extra component due to continuum coupling effects

“…Nevertheless, it neglects continuum coupling (or paircreation) effects, that give rise to virtual qq − qq (qqq − qq) components in the hadron wave function and determine a shift of the physical mass with respect to the bare mass [20]. These effects have already been studied by several authors in the baryon [21][22][23][24][25] and meson [26][27][28][29][30][31][32][33][34][35][36][37][38][39] sectors. Some examples are the resonance Λ(1405), strongly influenced by the nearbyKN channel [40], and the f 0 (980), that behaves remarkably as a KK molecule [41].…”