Final state interaction contribution to the response of confined relativistic particles

We report studies of the response of a massless particle confined by a potential. At large momentum transfer q it exhibits \tilde{y} or equivalently Nachtmann \xi scaling, and acquires a constant width independent of q. This width has a contribution from the final state interactions of the struck particle, which persists in the q->\infty limit. The width of the response predicted using plane wave impulse approximation is smaller because of the neglect of final state interactions in that approximation. However, the exact response may be obtained by folding the approximate response with a function representing final state interaction effects. We also study the response obtained from the momentum distribution assuming that the particle is on the energy shell both before and after being struck. Quantitative results are presented for the special case of a linear confining potential. In this case the response predicted with the on-shell approximation has correct values for the total strength, mean energy and width, however its shape is wrong.Comment: 11 pages, 3 figures, submitted to Phys. Rev.

Hadron Multiplicity in Semi-Inclusive Lepton-Nucleon and Lepton-Nucleus Scattering

We discuss multi-hadron production in both inelastic neutrino-nucleon interactions in the current fragmentation region and neutrino-nucleus collisions in the target fragmentation region. Our analysis, carried out within the framework of the quark-gluon string model, is mainly focused on the difference between these two processes. We show that the $Q^2$ dependence of hadron multiplicity in the current and target fragmentation regions is indeed completely different. The study of inelastic $\nu-A$ scattering in the target fragmentation region also provides new information on nuclear structure at small $N-N$ distances. The results of the proposed approach are in satisfactory agreement with the data recently obtained at CERN by the NOMAD Collaboration.Comment: Talk delivered a the Fourth International Conference on Perspectives in Hadronic Physics (ICTP, Trieste, Italy, May 2003). To be published in the Proceedings (EPJA

Final-state interactions in the response of nuclear matter

Final-state interactions in the response of a many-body system to an external probe delivering large momentum are normally described using the eikonal approximation, for the trajectory of the struck particle, and the frozen approximation, for the positions of the spectators. We propose a generalization of this scheme, in which the initial momentum of the struck particle is explicitly taken into account. Numerical calculations of the nuclear matter response at 1 $< |{\bf q}| <$ 2 GeV/c show that the inclusion of this momentum dependence leads to a sizable effect in the low energy tail. Possible implications for the analysis of existing electron-nucleus scattering data are discussed.Comment: 21 pages, 4 figure

Interpretation of y-scaling of the nuclear response

The behavior of the nuclear matter response in the region of large momentum transfer, in which plane wave impulse approximation predicts the onset of y-scaling, is discussed. The theoretical analysis shows that scaling violations produced by final state interactions are driven by the momentum dependence of the nucleon-nucleon scattering cross section. Their study may provide valuable information on possible modifications of nucleon-nucleon scattering in the nuclear medium.Comment: 4 pages with 3 figures. To appear in Physical Review Letter

Can a Highly Virtual Nucleon Experience Final State Interactions in Electron-Nucleus Scattering?

We discuss how the virtuality of the struck particle may affect the final state interactions in electron-nucleus scattering. The extent to which short range correlations inhibit rescattering taking place within the range of the repulsive core of the NN interaction is quantitatively analyzed. The possible modifications of the nucleon-nucleon scattering amplitude associated with the virtuality is also studied, within the framework of a nonrelativistic model. The results suggest that the on shell approximation can be safely employed in the kinematical region relevant to the analysis of the available inclusive data at large momentum transfer and low energy loss.Comment: 11 pages, 3 figures available upon request, Revte

Lepton-nucleus scattering in the impulse approximation regime

We discuss theoretical calculations of electron- and neutrino-nucleus scattering, carried out using realistic nuclear spectral functions and including the effect of final state interactions. Comparison between electron scattering data and the calculated inclusive cross sections off oxygen shows that the Fermi gas model fails to provide a satisfactory description of the measured cross sections, and inclusion of nuclear dynamics is needed. The role of Pauli blocking in charged-current neutrino induced reactions at low $Q^2$ is also analyzed.Comment: To be published in the Proceedings of NUFACT05 (Nucl. Phys. B, Proceedings Supplements

Many-body theory interpretation of deep inelastic scattering

We analyze data on deep inelastic scattering of electrons from the proton using ideas from standard many-body theory involving {\em bound} constituents subject to {\em interactions}. This leads us to expect, at large three-momentum transfer ${\bf{q}}$, scaling in terms of the variable $\tilde{y}=\nu-{\bf |q|}$. The response at constant ${\bf |q|}$ scales well in this variable. Interaction effects are manifestly displayed in this approach. They are illustrated in two examples.Comment: 10 pages, 4 figure

Gravitational waves from neutron stars described by modern EOS

The frequencies and damping times of neutron star (and quark star) oscillations have been computed using the most recent equations of state available in the literature. We find that some of the empirical relations that connect the frequencies and damping times of the modes to the mass and radius of the star, and that were previously derived in the literature need to be modified.Comment: 3 pages, 1+1 figures, to appear in the Proceedings of "XVI SIGRAV Conference", Vietri sul Mare (Italy), 13-16 September 200

Q**2-dependence of deep inelastic lepton scattering off nuclear targets

Deep inelastic scattering of leptons off nuclear targets is analized within the convolution model taking into account nucleon-nucleon correlations. We show that in the nuclear medium nucleons are distributed according to a function that exhibits a sizeable Q**2-dependence and reduces to the ordinary light-cone distribution in the Bjorken limit. At Q**2 1 this Q**2-dependence turns out to be stronger than the one associated with the nucleon structure function, predicted by pertubative quantum chromodynamics.Comment: 11 pages including figs. Figs. can be sent by PS-fil