Final state interactions effects on kinetic energy sum spectra in nonmesonic weak decay

We analyze the effect of final state interactions (FSI) on coincidence spectra in nonmesonic hypernuclear weak decay, ΛN → nN, as a function of the kinetic energy sum, EnN = En + EN , both for np and nn events. Adopting a formalism recently developed, the effects of FSI originated from the interaction between the outgoing nucleons and those in the residual core are included analytically in a very simple way within the eikonal approximation through the modification of the emerging particles momenta. Numerical results are shown for 5 ΛHe and 12 Λ C hypernucleus. We found that coincidence spectra are only slightly modified and the disagreement between theory and experimental data still persists, mainly for nn events in ΛHe where enough statistics exists. We conclude that admixtures of excitations in the final state produced by FSI need to be added to our approach in order to improve the agreement with data.