ω- πγtransition form factor in proton-proton collisions

Abstract

Dalitz decays of ω and ρ mesons, ω → π 0 γ * → π 0 e + e − and ρ 0 → π 0 γ * → π 0 e + e − , produced in pp collisions are calculated within a covariant effective meson-nucleon theory. We argue that the ω transition form factor F ω→π 0 γ * is experimentally accessible in a fairly model independent way in the reaction pp → ppπ 0 e + e − for invariant masses of the π 0 e + e − subsystem near the

Di-electrons from η -meson Dalitz decay in proton-proton collisions

“…Contrary to the transition FF of vector meson production [18], the η meson FF, computed within such an approach, exhibits a rather good agreement with previous data [5,20,21,22].…”

“…Such a choice of kinematical variables is extremely useful if one considers specific classes of Feynman diagrams which allow to separate some vertices in a factorized form. Then in the total cross section some integrations can be performed analytically (see [3,18]). For the present task we need to consider only such types of diagrams which allows to factorize the meson decay vertex from the parts describing the creation of the meson in a NN interaction.…”

“…Equation (3.27) allows one to rewrite the differential cross section (3.1) in a factorized form as well, 29) where the integral over the final di-electron and photon variables has been performed analytically (see for details [3,18]). dΓ η→γe + e − /ds γ * is defined by eq.…”

“…The effective parameters of the Lagrangians (3.2 -3.6) which determine the pure nucleon current diagrams are basically the ones from the OBE Bonn potential [34] which have been used in our previous calculations for vector meson (ω, ρ and φ) production in NN interactions [12,18], see Tab [34]. The coupling constants g ωωη and g ρρη for the conversion current have been calculated (Note that a naive direct calculations of these constants within the VMD model can provide slightly larger values g V V η ∼ 6.0.)…”

η′ meson production in nucleon-nucleon collisions near the threshold

“…The invariant amplitude T is evaluated here within a phenomenological meson-nucleon theory based on effective interaction Lagrangians (see [26,27,29,32,33]) which include (i) isoscalar mesons: scalar (σ), pseudo-scalar (η), vector (ω), (ii) isovector mesons: scalar (a 0 ), pseudo-scalar (π) and vector (ρ): 8) where N and Φ denote the nucleon and meson fields, respectively, and bold face letters stand for iso-vectors. All couplings with off-mass shell particles are dressed by monopole …”