Composite particle production in high-energy reactions and size of production source

Production cross sections of composite particles at ${\ominus }_{\mathrm{lab}}=90\mathrm{}°$ (the target-rapidity region) from 12-GeV proton reaction on nuclear targets have been measured. The particle spectra were analyzed with the coalescence model, and the radius of the production source was deduced to be $R_0^{\mathrm{rms}}=1.7\mathrm{}\pm 0.5$ fm. The radius is significantly smaller than the nuclear radii, and is independent on the target nuclear mass within uncertainties.