Nucleus as a color filter in QCD: Hadron production in nuclei

Abstract

The data on hadron production in nuclei exhibit two striking regularities which are not readily explained by conventional hadron dynamics: (1) The mass-number dependence ${\mathrm{A}}^{\mathrm{\ensuremath{\alpha}}({\mathrm{x}}_{\mathrm{F}})}$ of inclusive production cross sections has a universal power \ensuremath{\alpha}(${\mathrm{x}}_{\mathrm{F}}$), which is independent of the produced hadron. (2) The A dependence of J/\ensuremath{\psi} production in nuclei has two distinct components: an ${\mathrm{A}}^{1}$ contribution at low ${\mathrm{x}}_{\mathrm{F}}$ and an anomalous ${\mathrm{A}}^{2/3}$ contribution which dominates at large ${\mathrm{x}}_{\mathrm{F}}$. We show that both phenomena can be understood in QCD as a consequence of the nucleus filtering out small, color-singlet Fock-state components of the incident-hadron wave function.