Model-independent view on the low-mass proton-antiproton enhancement

Abstract

We present a simple interpretation of the recently observed nearthreshold proton-antiproton enhancement. It is described by a set of low-energy parameters deduced from the analysis of NN experiments at LEAR. We predict a related effect in photoproduction reaction under study by CLAS collaboration.Low-mass baryon-antibaryon enhancement has recently been observed in the decays. On the theoretical side this discovery has been discussed by several authors [4,5,6,7]. In [4] the near-threshold effect has been considered either as a gluonic state or as a result of the quark fragmentation process. In [5] it has been attributed to the Breit colorspin interaction while in [6] it has been regarded as caused by peripheral one-pion-exchange potential. The quantum numbers corresponding to the observed enhancement are discussed in [7].The purpose of the present work is to show that the recently observed near-threshold pp enchancement may be understood invoking the knowledge on NN interaction gained at the Low Energy Antiproton Ring (LEAR) at CERN. The LEAR results may be schematically subdivided into three groups:(i) meson spectroscopy, (ii) baryonium searches, (iii) NN interaction: scattering, annihilation, protonium spectroscopy.

Study of the baryon–antibaryon low-mass enhancements in charmless three-body baryonic B decays

“…[5,6] and elaborated more recently in Refs. [7,8,9]. The same peaking behavior near threshold has been found in baryonic J/ψ decays [10] as well, indicating that this may be a universal phenomenon.…”

“…Possible explanations include intermediate (gluonic) resonant states or non-perturbative QCD effects of the quark fragmentation process [7,8]. Alternatively, the dynamical picture can be replaced by an effective range analysis with a baryon form factor [9]. To distinguish among the above hypotheses for the production mechanism, we study the angular distributions of the threshold enhancements in the helicity frame for the…”

Near threshold enhancement of thepp¯mass spectrum inJ/Ψdecay

“…An entirely different and much more conventional interpretation of the observed enhancement was suggested in several recent works [17][18][19]. These authors argue that the enhancement is primarily due to the final state interaction (FSI) between the produced proton and antiproton.…”

“…These authors argue that the enhancement is primarily due to the final state interaction (FSI) between the produced proton and antiproton. Specifically, it was shown within the scattering length approximation [17] that a calculation with a complex S-wave scattering length extracted from an effectiverange analysis of pp scattering data can reproduce the shape of the pp mass distribution close to the threshold.…”

“…As just mentioned, the investigations of Kerbikov et al [17] as well as those of Bugg [18] rely on the scattering length approximation. But it remains unclear over which energy range this approximation can provide a reliable representation of the energy dependence of the pp amplitude.…”