Head-on collision of dust acoustic solitons in a nonextensive plasma with variable size dust grains of arbitrary charge.

The head-on collision of two dust acoustic solitons (DASs) in a nonextensive plasma with positive or negative dust grains fluid including the effect of dust size distribution (DSD) is studied. The phase shifts for the two solitons due to the collision are derived by applying the extended Poincaré-Lighthill-Kuo (PLK) method. The influences of the power law DSD and the nonextensivity of plasma particles on the characteristic properties of the head-on collision of DASs are analyzed. It is found that the phase shifts can vanish, only for the case of positive dust grains, for certain values and ranges of the dust grain radius and the entropic index of ions (q_{i}). Also, they undergo a cutoff in the range of q_{i}>1 for the subextensive distribution. A brief discussion of possible applications in laboratory and space plasmas is included.