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Stijn Janssen

Publications and source records attributed to Stijn Janssen.

2 recordsLinked to original sources

Spin-dependent correlations and the semi-exclusive ^{16}O(e,e'p) reaction

The effect of central, tensor and spin-isospin nucleon-nucleon correlations upon semi-exclusive ^{16}O(e,e'p) reactions is studied for Q^2 and Bjorken x values in the range $0.2 \lesssim Q^2 \lesssim 1.1 (GeV/c)^2$ and 0.15 $\lesssim$ x $\lesssim$ 2. The fully unfactorized calculations are performed in a framework that accounts not only for the dynamical coupling of virtual photons to correlated nucleon pairs but also for meson-exchange and $Δ_{33}$-isobar currents. Tensor correlations are observed to produce substantially larger amounts of semi-exclusive ^{16}O(e,e'p) strength than central correlations do and are predominantly manifest in the proton-neutron knockout channel. With the exception of the $x \approx 2$ case, in all kinematical situations studied the meson-exchange and isobar currents are a strong source of A(e,e'p) strength at deep missing energies. This feature gives the A(e,e'p) strength at deep missing energies a pronounced transverse character.

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Meson and Isobar Degrees of Freedom in A($\vec{e},e'\vec{p}$) reactions at $0.2 \leq Q^2 \leq 0.8 (GeV/c)^2$

The effect of meson and isobar degrees of freedom in A($\vec{e},e'\vec{p}$) and A(e,e'n) is studied for four-momentum transfers Q^2 in the range between 0.2 and 0.8 (GeV/c)^2. The calculations are performed in a non-relativistic framework with explicit (N,Δ,π) degrees-of-freedom. For the whole range of momentum transfers under investigation the relative effect of the meson-exchange and isobar degrees of freedom is significant. At low missing momenta and quasi-elastic conditions, a tendency to reduce the (e,e'p) and (e,e'n) differential cross sections is noticed. The greatest sensitivity is found in the interference structure functions $W_{LT}$ and $W_{TT}$. The recoil polarization observables, on the other hand, are moderately affected by the meson-exchange and $Δ$-isobar currents.

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