Pion production and charged-particle multiplicity selection in relativistic nuclear collisions

Spectra of positive pions with energies of 15-95 MeV were measured for high energy proton, ⁴He, ²⁰Ne, and ⁴⁰Ar bombardments of targets of ²⁷Al, ⁴⁰Ca, 107,109Ag, ¹⁹⁷Au, and ²³⁸U. A Si-Ge telescope was used to identify charged pions by dE/dx-E and, in addition, stopped π⁺ were tagged by the subsequent muon decay. In all, results for 14 target-projectile combinations are presented to study the dependence of pion emission patterns on the bombarding energy (from E/A=0.25 to 2.1 GeV) and on the target and the projectile masses. In addition, associated charged-particle multiplicities were measured in an 80-paddle array of plastic scintillators, and used to make impact parameter selections on the pion-inclusive data.NUCLEAR REACTIONS U(²⁰Ne, π⁺), E/A=250 MeV; U(⁴⁰Ar, π⁺), Ca(⁴⁰Ar, π⁺), U(²⁰Ne, π⁺), Au(²⁰Ne, π⁺), Ag(²⁰Ne, π⁺), Al(²⁰Ne, π⁺), U(⁴He, π⁺), Al(⁴He, π⁺). E/A=400 MeV; Ca(⁴⁰Ar, π⁺), U(²⁰Ne, π⁺), U(⁴He, π⁺), U(p, π⁺), E/A=1.05), GeV; U(²⁰Ne, π⁺), E/A=2.1 GeV; measured σ(E, θ), inclusive and selected on associated charged-particle multiplicity.