${\pi }^{+}-{\pi }^{-}$ Asymmetry and the Neutron Skin in Heavy Nuclei

Abstract

In heavy nuclei the spatial distribution of protons and neutrons is different. At CERN SPS energies production of ${\pi }^{+}$ and ${\pi }^{-}$ differs for $pp$, $pn$, $np$ and $nn$ scattering. These two facts lead to an impact parameter dependence of the ${\pi }^{+}$ to ${\pi }^{-}$ ratio in ${}^{208}Pb{+}^{208}Pb$ collisions. A recent experiment at CERN seems to confirm qualitatively these predictions. It may open a possibility for determination of neutron density distribution in nuclei.

Comments: 6 pages and 2 figures, a talk by A.Szczurek at the international conference MESON2004, June 4-8, Cracow, Poland