Abstract
Production cross sections of superheavy nuclei Rf and Hs for asymmetric and nearly symmetric projectile-target combinations are systematically studied within the framework of the dinuclear system model. The calculated results show that the production cross sections are strongly dependent on the symmetry of reaction systems. The obtained results are in good agreement with the available experimental data for asymmetric reaction systems. For nearly symmetric systems, the model gives opposite results with coupled channel model in which surface vibration and nucleon transfer are included.