Unraveling the reaction mechanism for large alpha production and incomplete fusion in reactions involving weakly bound stable nuclei

The origin of the large $\alpha$ particle production and incomplete fusion in reactions involving weakly-bound $\alpha$+$x$ cluster nuclei still remains unresolved. While (two-step) process breakup followed by capture ``free" complementary fragment ($x$) is widely believed to be responsible, a few recent studies suggest dominant role (direct) stripping. To achieve an unambiguous experimental discrimination between these two processes, coincidence measurement outgoing particles $\gamma$ rays from heavy residues has been performed for $^7$Li($\alpha$+triton)+$^{93}$Nb system. Proper choice kinematical conditions allowed first time significant population region accessible only direct triton stripping not ``free'' (from three-body continuum). This result, also supported cluster-transfer calculation, clearly establishes dominance cluster-stripping mechanism alpha production.