Forward-backward multiplicity correlations of target fragments in nucleus-emulsion collisions at a few hundred MeV/u

The forward-backward multiplicity and correlations of a target evaporated fragment （black track particle） and target recoiled proton （grey track particle） emitted from 150 A MeV 4He, 290 A MeV ^12C, 400 A MeV ^12C, 400 A MeV ^20Ne and 500 A MeV ^56Fe induced different types of nuclear emulsion target interactions are investigated. It is found that the forward and backward averaged multiplicity of a grey, black and heavily ionized track particle increases with the increase of the target size. The averaged multiplicity of a forward black track particle, backward black track particle, and backward grey track particle do not depend on the projectile size and energy, but the averaged multiplicity of a forward grey track particle increases with an increase of projectile size and energy. The backward grey track particle multiplicity distribution follows an exponential decay law and the decay constant decreases with an increase of target size. The backward-forward multiplicity correlations follow linear law which is independent of the projectile size and energy, and the saturation effect is observed in some heavy target data sets.