arXiv subjects
Publications and source records attributed to S. Boffi.
Nuclear Compton scattering in the $Δ$-resonance region is reconsidered within the framework of the $Δ$-hole model. The different role of the resonant and non-resonant contributions to the transition amplitudes is discussed and their effect is investigated by comparing the results of calculation with recent data also taken with polarized photons.
The response to longitudinally polarized electrons in coincident out-of-plane ($\vec{\mathrm e},{\mathrm e}'{\mathrm p}$) reaction is discussed to study the role of final state interactions and quantum interference between different reaction channels, i.e. between direct (quasi) elastic proton emission and baryon resonance production. The high-energy suppression of this effect due to colour transparency is also discussed. Results are given for the $^{12}$C($\vec{\mathrm e},{\mathrm e}'{\mathrm p}$)$^{11}$B$_{\mathrm {g.s.}}$
Effects of nucleon-nucleon correlations on exclusive $(e,e'p)$ reactions on closed-shell nuclei leading to single-hole states are studied using $^{16}O(e,e'p)^{15}N$ ($6.32$ MeV, $3/2^-$) as an example. The quasi-hole wave function, calculated from the overlap of translationally invariant many-body variational wave functions containing realistic spatial, spin and isospin correlations, seems to describe the initial state of the struck proton accurately inside the nucleus, however it is too large at the surface. The effect of short-range correlations on the final state is found to be largely cancelled by the increase in the transparency for the struck proton. It is estimated that the values of the spectroscopic factors obtained with the DWIA may increase by a few percent due to correlation effects in the final state.
We suggest the measurement of the integrated asymmetry of teh missing momentum distribution in (e,e$'$p)reactions to check color transparency effects at intermediate momentum transfers.
We suggest the measurement of the integrated asymmetry of teh missing momentum distribution in (e,e$'$p)reactions to check color transparency effects at intermediate momentum transfers.
We discuss the unexpected enhancement of the $N^*$ electroproduction on nuclei recently observed in the $(γ^*,pπ^-)$ measurement. A mechanism which is able to explain this result is proposed. To clarify the situation, we suggest to perform a new kind of experiment within well specified kinematic conditions.
The dynamics of nuclear transparency in hard nuclear reactions is studied by an expansion of the correlator of the hard scattering operator on a hadronic basis. Colour transparency appears as an effect of interference between the amplitudes corresponding to the final state interaction of different intermediate baryonic states. We find that colour transparency occurs even at moderate momentum transfers if one chooses the missing momentum of the struck nucleon by appropriate kinematics. In general, the role of the Fermi-motion is found to be crucial; without it, any effect of anomalous nuclear transparency would be impossible.