Coherence Effects in Charmonium Production off Nuclei : Consequences for J/ψSuppression
Abstract
Description
The probabilistic Glauber formula for nuclear absorption used in the literature is only valid at low energies and $x_+ \simeq 0$. Due to energy conservation, $σ_{abs}$ is replaced by an effective cross-section $σ_{abs} + x_+^γ$ ($σ_{c\bar{c}-N} - σ_{abs})$ which increases with $x_+$ and tends to the total $c\bar{c}-N$ cross-section $σ_{c\bar{c}-N}$. Experimental data can be described with $σ_{abs} \sim 4 ÷5$mb and $σ_{c\bar{c}-N} \sim 15 ÷20$mb. At high energies, due to the increase of the coherence length, this formula changes. The main change is the replacement of $σ_{abs}$ by $σ_{c\bar{c}-N}$ -- for all values of $x_+$, as $s \to \infty$. Thus, if $σ_{c\bar{c}-N} > σ_{abs}$ the $J/ψ$ suppression due to nuclear interaction will increase with energy.
Talk presented at the International Workshop on Charm Production, ECT*, Trento, June 2002
Talk presented at the International Workshop on Charm Production, ECT*, Trento, June 2002