Photon-induced two-nucleon knockout reactions to discrete final states

Cross sections and photon asymmetries of the exclusive 16O(\gamma,pn)14N and 16O(\gamma,pp)14C knockout reactions are calculated for transitions to the low-lying discrete final states of the residual nucleus in the photon-energy range between 100 and 400 MeV. Exclusive reactions may represent a test of reaction mechanisms and a promising tool for investigating the dynamics of nucleon pairs in different states. Cross sections and asymmetries for both (\gamma,pn) and (\gamma,pp) turn out to be only slightly affected by short-range correlations and dominated by two-body currents. Therefore, two-nucleon knockout reactions induced by real photons appear well suited to investigate the nuclear current and the selectivity of individual transitions to its different components.Comment: 21 pages, 16 postscript figure

Neutrino-Nucleus Quasi-Elastic Scattering in a Relativistic Model

A relativistic distorted-wave impulse-approximation model is applied to neutral-current and charged-current quasi-elastic neutrino-nucleus scattering. The effects of final state interactions are investigated and the sensitivity of the results to the strange nucleon form factors is discussed in view of their possible experimental determinationComment: 7 pages, 3 figures Proc. of the XXV International Workshop on Nuclear Theory, 26 June- 1 July, 2006 Rila, Bulgari

On the NN-final-state-interaction in the 16O(e,e′pp)^{16}{O}(e,e' pp) reaction

The influence of the mutual interaction between the two outgoing nucleons (NN-FSI) in the $^{16}{O}(e,e' pp)$ reaction has been investigated. Results for various kinematics are discussed. In general, the effect of NN-FSI depends on kinematics and the chosen final state in the excitation spectrum of $^{14}{C}$.Comment: 12 pages Revtex including 4 postscript figure

The NN-final-state-interaction in two-nucleon-knockout reactions

The influence of the mutual interaction between the two outgoing nucleons (NN-FSI) in electro- and photoinduced two-nucleon knockout from $^{16}O$ has been investigated perturbatively. It turns out that the effect of NN-FSI depends on the kinematics and on the type of reaction considered. In the kinematics studied so far, the effect is larger in pp- than in pn-knockout and in electron induced than in photoinduced reactions.Comment: 10 pages including 9 postscript figures, contribution to the 6th workshop on "Electromagnetically Induced Two-Hadron Emission", Pavia, September 24-27, 200

Effects of nuclear correlations on the 16^{16}O(e,e′pN)(e,e'pN) reactions to discrete final states

Calculations of the $^{16}$O$(e,e'pN)$ cross sections to the ground state and first excited levels of the $^{14}$C and $^{14}$N nuclei are presented. The effects of nuclear fragmentation have been obtained in a self-consistent approach and are accounted for in the determination of the two-nucleon removal amplitudes. The Hilbert space is partitioned in order to compute the contribution of both long- and short-range effects in a separate way. Both the two-proton and the proton-neutron emission cross sections have been computed within the same models for the reaction mechanism and the contribution from nuclear structure, with the aim of better comparing the differences between the two physical processes. The $^{16}$O$(e,e'pp)$ reaction is found to be sensitive to short-range correlations, in agreement with previous results. The $^{16}$O$(e,e'pn)$ cross section to $1^+$ final states is dominated by the $\Delta$ current and tensor correlations. For both reactions, the interplay between collective (long-range) effects and short-range and tensor correlations plays an important role. This suggests that the selectivity of $(e,e'pN)$ reactions to the final state can be used to probe correlations also beyond short-range effects.Comment: 13 pages, 9 figure

On the treatment of the Δ\Delta-contribution in electromagnetic pppp-knockout reactions

The treatment of the $\Delta$-current and its contribution in the exclusive $^{16}$O$(e,e'pp)^{14}$C and $^{16}$O$(\gamma,pp)^{14}$C knockout reactions are investigated in combination with the effects of correlations. Different parametrizations of the effective $\Delta$-current and different treatments of correlations in the two-nucleon overlap function are considered. The results are presented and discussed for a suitable choice of kinematics. It is found that the investigation of different mutually supplementing kinematics is necessary to resolve the uncertainties in the theoretical ingredients and extract clear and unambiguous information on correlations.Comment: 15 pages, 9 figures, EPJA styl

NN correlations and final-state interactions in (e,e'NN) reactions

After a brief overview of relevant studies on one-nucleon knockout showing the importance of quantitatively understanding the origin of the quenched spectroscopic factors extracted from data, attention is focussed on two-nucleon emission as a suitable tool to investigate nucleon-nucleon correlations inside complex nuclei. In particular, direct (e,e$'$pp) and (e,e$'$pn) reactions are discussed, and the role of final-state interactions is studied. The influence of the mutual interaction between the two outgoing nucleons is shown to depend on the kinematics and on the type of the considered reaction.Comment: 13 pages, 4 figures. Proceedings of 2nd Int. Conf. on Nuclear and Particle Physics with CEBAF at Jefferson Lab, Dubrovnik, 26-31 May 2003, to be published on Fyzika

Polarization observables in (γ⃗,N⃗N{\vec \gamma},{\vec N}N) reactions

The formalism of (${\vec \gamma},{\vec N}N$) reactions is given where the incident photon is polarized and the outgoing nucleon polarization is detected. Sixteen structure functions and fifteen polarization observables are found in the general case, while only eight structure functions and seven polarizations observables survive in coplanar kinematics. Numerical examples are presented for the $^{16}$O($\gamma,pn$) and $^{16}$O($\gamma,pp$) reactions. The transitions to the ground state of $^{14}$C and $^{14}$N are calculated in a model where realistic short-range and tensor correlations are taken into account for the $pn$ pair, while short-range and long-range correlations are included in a consistent way for $pp$ pairs. The effects of the one-body and two-body components of the nuclear current and the role of correlations in cross sections and polarizations are studied and discussed.Comment: 27 pages, 16 figures (eps). Revised version. To be published in EPJ

One- and Two-Nucleon Structure form Green's Function Theory

We review some applications of self-consistent Green's function theory to studies of one- and two-nucleon structure in finite nuclei. Large-scale microscopic calculations that employ realistic nuclear forces are now possible. Effects of long-range correlations are seen to play a dominant role in determining the quenching of absolute spectroscopic factors. They also enhance considerably (e,e'pn) cross sections in superparallel kinematics, in agreement with observations.Comment: Proceedings of the International Symposium on "Forefronts of Researches in Exotic Nuclear Structures" (Niigata2010)