Deuteron breakup at extreme forward angles: Failure of a pure Coulomb dissociation description

We present an analysis of recent measurement of the 56 MeV deuteron breakup data on 12C, 40Ca, and 208Pb targets taken by Okamura et al.. The cross section measured at θp=θn=0 degree was claimed to be a strong evidence of Coulomb breakup, especially in light nuclei. However, the single-step pure Coulomb breakup formalism fails to describe both the magnitude and the shape of the triple differential cross section even in light nuclei. At 56 MeV incident deuteron energy, the nuclear interference effect is found to be significant in all the above nuclei. The prior form distorted-wave Born-approximation calculations with unusual optical potentials in the exit channel can reproduce the highly asymmetric shapes of the triple differential cross section at the extreme forward angle, but, fail to give their exact magnitude. The possible role of multistep processes is discussed. copyright 1996 The American Physical Society