Quasi-two-body decays of nonstrange baryons

Abstract

We examine the decays of nonstrange baryons to the final states ∆π, N ρ, N η, N η ′ , N ω, N 1 2 + (1440)π, and ∆ 3 2 + (1600)π, in a relativized pair-creation ( 3 P 0 ) model which has been developed in a previous study of the N π decays of the same baryon states. As it is our goal to provide a guide for the possible discovery of new baryon states at CEBAF and elsewhere, we examine the decays of resonances which have already been seen in the partial-wave analyses, along with those of states which are predicted by the quark model but which remain undiscovered. The level of agreement between our calculation and the available widths from the partial-wave analyses is encouraging.

Baryons as relativistic three-quark bound states

“…The third term comprises two-photon effects and its currently accepted value is E TPE = 0.0332 (20) meV [677], with similar numbers obtained by various authors (see Table 6.1 in Ref. [643] for a compilation).…”

“…Consequently, the integration can be performed analytically and for m q = 0 one obtains two solutions, 20) which are connected at p 2 = Λ 2 and lead to the non-trivial quark mass function shown in the left panel of Fig. 3.3.…”

“…The Roper is unusually broad and not well described within the non-relativistic constituent-quark model (see [18] and references therein), which predicts the wrong mass ordering between the Roper and the nucleon's parity partner N (1535) and the wrong sign of the γp → N (1440) transition amplitude. Although some of these deficiencies were later remedied by relativistic quark models [18][19][20][21][22], they have led to longstanding speculations about the true nature of this state being the first radial excitation of the nucleon or perhaps something more exotic.…”

“…), one can establish a system of coupledchannel equations for the T-matrix. For example, keeping only the N γ and N π channels in the low-energy region leads to the scattering equation 20) where G π and G γ are the two-body nucleon-pion and nucleon-photon propagators and the scattering matrices correspond to N π scattering (ππ), pion electroabsorption/electroproduction (πγ, γπ) and nucleon Compton scattering (γγ). Neglecting also electromagnetic effects leaves two equations for T ππ and T γπ which are shown in the left of Fig.…”

Photoproduction for N* and Related Topics at LEPS/LEPS2

“…However, most of them are not identified experimentally and called 'missing resonances'. They are predicted to decay not only to the πN channel but also to KΛ, KΣ, ηN, ωN, and π∆ channels by Capstick and Roberts [1,2]. Since only πN channel has been extensively studied so far, N * studies using other channels are very important.…”