M. B. Gay Ducati — Page 6

arXiv1993

Diffraction and the Gluon Mass

We recently proposed a QCD-Pomeron described by the exchange of two non-perturbative gluons characterized by a dynamically generated gluon mass. It is here shown that data on elastic scattering, exclusive $ρ$ production in deep inelastic scattering and the $J/Ψ$-nucleon total cross-section can be successfully described in terms of a single gluon mass $m_g\simeq0.37$~GeV. We observe that the total cross sections of hadrons with small radii, such as $J/Ψ$, have a marked dependence on the effective gluon mass.

hep-ph↗

arXiv1993

$J/ψ$ at small-$x$

It has been suggested that the suppression of $J/ψ$ production in heavy nuclei is a signature of the formation of quark-gluon plasma. We here show that this phenomenon can be understood in terms of conventional physics, {\it i.e.} {\it i)} perturbative QCD, {\it ii)} the parton recombination implementation of shadowing in the initial state, and {\it iii)} final state interactions with the hadronic debris of the nuclear target. Unlike previous calculations we include both the direct $J/ψ$ production and its production via radiative $χ$ decays ($χ_J \to J/ψ+ γ$). We are able to reproduce the experimental data including their small-$x$ behavior. We emphasize the importance of studying the $x_2$-dependence of the ratio $σ(b A)/σ(b N)$, where $b$ designates the beam and $x_2$ is the momentum fraction of the parton from the nuclear target.

hep-ph↗