Progress in the determination of the $J/\psi -\pi$ cross section

Abstract

Improving previous calculations, we compute the $J/\psi \pi \to charmedmesons$ cross section using QCD sum rules. Our sum rules for the $J/\psi \pi \to \bar{D}{D}^{\ast }$, $D{\bar{D}}^{\ast }$, ${\bar{D}}^{\ast }{D}^{\ast }$ and $\bar{D}D$ hadronic matrix elements are constructed by using vaccum-pion correlation functions, and we work up to twist-4 in the soft-pion limit. Our results suggest that, using meson exchange models is perfectly acceptable, provided that they include form factors and that they respect chiral symmetry. After doing a thermal average we get $<{\sigma }^{\pi J/\psi }v>\sim 0.3$ mb at $T=150\text{MeV}$.

Comments: 22 pages, RevTeX4 including 7 figures in ps files