Negative pion production by 800 MeV/A C,Ne, and Ar beams

Energy and angular distributions of π's produced in relativistic heavy-ion collisions have been measured at 800 MeV/A incident energy. Cross sections for low-energy pions (E_cm ≈ 100–200 MeV) are forward and backward peaked in the nucleon-nucleon c.m. frame. Such anisotropy becomes weaker for higher energy pions. The shape of the energy spectra at θ_cm = 90° is approximately exponential. Their slopes are steeper than those observed for protons. The data are discussed in terms of several models.