348 research outputs found
Slow proton production in semi-inclusive DIS off nuclei: the role of final state interaction
The effects of the final state interaction on the production of slow protons
in semi-inclusive deep-inelastic lepton scattering off nuclei is considered
within the spectator mechanism and a realistic approach in which the
rescattering in the medium of both the recoiling proton and the hadronizing
nucleon debris are taken into account.Comment: 4 pages, 4 figures, to appear in the Proceedings of the "Fifth
International Conference on Perspectives in Hadronic Physics" held at ICTP,
Trieste, 22 - 26 May 200
Effects of Ground-State Correlations on High Energy Scattering off Nuclei: the Case of the Total Neutron-Nucleus Cross Section
With the aim at quantitatively investigating the longstanding problem
concerning the effect of short range nucleon-nucleon correlations on scattering
processes at high energies, the total neutron-nucleus cross section is
calculated within a parameter-free approach which, for the first time, takes
into account, simultaneously, central, spin, isospin and tensor nucleon-nucleon
(NN) correlations, and Glauber elastic and Gribov inelastic shadowing
corrections. Nuclei ranging from 4He to 208Pb and incident neutron momenta in
the range 3 GeV/c - 300 GeV/c are considered; the commonly used approach which
approximates the square of the nuclear wave function by a product of one-body
densities is carefully analyzed, showing that NN correlations can play a
non-negligible role in high energy scattering off nuclei.Comment: 5 pages, 3 figure
A non factorized calculation of the process ^3He(e,e'p)^2H at medium energies
The exclusive process ^3He(e,e^\prime p)^2H has been analyzed using realistic
few-body wave functions corresponding to the AV18 interaction and treating the
final state interaction (FSI) within the Eikonal Approximation to describe the
multiple rescattering of the struck nucleon with the nucleons of the spectator
two-nucleon system. Calculations have been performed in momentum space so that
the nucleon electromagnetic current could be left in the fully covariant form
avoiding by this way non relativistic reductions and the factorization
approximation. The results of calculations, which are compared with recent JLab
experimental data, show that the left-right asymmetry exhibit a clear
dependence upon the multiple scattering in the final state and demonstrate the
breaking down of the factorization approximation at \phi=0 i.e. for "negative"
and large \geq 300MeV/c values of the missing momentum.Comment: 14 pages, 6 figure
Sivers Asymmetry for the proton and the neutron
A formalism is presented to evaluate the Sivers function in constituent quark
models. A non-relativistic reduction of the scheme is performed and applied to
the Isgur-Karl model. The results obtained are consistent with a sizable Sivers
effect and the signs for the u and d flavor contributions turn out to be
opposite. The Burkardt Sum Rule is fulfilled to a large extent. After the
estimate of the QCD evolution of the results from the momentum scale of the
model to the experimental one, a reasonable agreement with the available data
is obtained. A calculation of nuclear effects in the extraction of neutron
single spin asymmetries in semi-inclusive deep inelastic scattering off 3He is
also described. In the kinematics of forth-coming experiments at JLab, it is
found that the nuclear effects arising within an Impulse Approximation approach
are under control.Comment: 8 pages, 3 figures, Invited talk at the "6th International Conference
on Hadronic Physics", ICTP, Trieste, Italy, 12-16 May 2008. To appear in AIP
Proceedings Serie
On the effects of the final state interaction in the electro-disintegration of the deuteron at intermediate and high energies
The role of the final state interactions (FSI) in the inclusive quasi-elastic
disintegration of the deuteron is investigated treating the two-nucleon final
state within the exact continuum solutions of the non-relativistic Schroedinger
equation, as well as within the Glauber multiple scattering approach. It is
shown that for values of the Bjorken scaling variable both
approaches provide similar results, unless the case , where
they appreciably disagree. It is demonstrated that present experimental data,
which are mostly limited to a region of four-momentum transfer () where the Center-of-Mass energy of the final state is below the
pion threshold production, can be satisfactorily reproduced by the approach
based on the exact solution of the Schroedinger equation and not by the Glauber
approach. It is also pointed out that the latter, unlike the former, does not
satisfy the inelastic Coulomb sum rule, the violation being of the order of
about 20%.Comment: 16 LaTeX pages, 10 eps-figures, 1 tabl
Calculations of the Exclusive Processes 2H(e,e'p)n, 3He(e,e'p)2H and 3He(e,e'p)(pn) within a Generalized Glauber Approach
The exclusive processes 2H(e,e'p)n, 3He(e,e'p)2H and 3He(e,e'p)(pn), have
been analyzed using realistic few-body wave functions and treating the final
state interaction (FSI) within a Generalized Eikonal Approximation (GEA), based
upon the direct calculation of the Feynman diagrams describing the rescattering
of the struck nucleon with the nucleons of the A-1 system. The approach
represents an improvement of the conventional Glauber approach (GA), in that it
allows one to take into account the effects of the nuclear excitation of the
system on the rescattering of the struck nucleon. Using realistic
three-body wave functions corresponding to the AV18 interaction, the results of
our parameter free calculations are compared with available experimental data.
It is found that in some kinematical conditions FSI effects represent small
corrections, whereas in other kinematics conditions they are very large and
absolutely necessary to provide a satisfactory agreement between theoretical
calculations and experimental data. It is shown that in the kinematics of the
experimental data which have been considered, covering the region of missing
momentum and energy with p_m < 0.6 GeV/c and E_m < 100 MeV in the perpendicular
kinematics, the GA and GEA predictions differ only by less than 3-4 %.Comment: Typos detected and removed while Proof reading. Physical Review C. in
Pres
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
Finite formation time effects in quasi-elastic scattering on nuclear targets
The problem of the final state interaction in quasi-elastic
scattering at large , is investigated by exploiting the idea that the
ejected nucleon needs a finite amount of time to assume its asymptotic form. It
is shown that when the dependence of the scattering amplitude of the ejected
nucleon on its virtuality is taken into account, the final state interaction is
decreased. The developed approach is simpler to implement than the one based on
the color transparency description of the damping of the final state
interaction, and is essentially equivalent to the latter in the case of the
single rescattering term. The process on the deuteron is numerically
investigated and it is shown that, at , appreciable finite formation time
effects at of the order of 10 (GeV/c) are expected.Comment: 23 pages, 3 figure
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