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Register a new userInclusive Spectra of (p,xp) and (p,xd) Reactions on $^{90,92}$Zr and $^{92}$Mo Nuclei at E$_{p}$=30.3 MeV
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New experimental data for the inclusive reactions (p,xp) and (p,xd) on isotopes of the nuclei $^{90,92}$Zr and $^{92}$Mo, have been measured at E$_{p}$=30.3 MeV, which has not been investigated in detail so far. We show the extension of the pre-equilibrium reactions to this energy region and interpret the results of these experiments. Moreover, we display the mechanism of the reaction and the level of energy-dependence. The adequacy of the theoretical models in explaining the measured experimental data is also discussed. In our theoretical analysis, the contributions of multi-step direct and compound processes in the formation of cross-sections are determined and we assert that the traditional frameworks are valid for the description of the experimental data.
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The isoscalar giant monopole, dipole, and quadrupole strength distributions have been deduced in $^{90, 92}$Zr, and $^{92}$Mo from background-free spectra of inelastic $alpha$-particle scattering at a beam energy of 385 MeV at extremely forward angles, including 0$^{circ}$. These strength distributions were extracted by a multipole-decomposition analysis based on the expected angular distributions of the respective multipoles. All these strength distributions for the three nuclei practically coincide with each other, affirming that giant resonances, being collective phenomena, are not influenced by nuclear shell structure near $Asim$90, contrary to the claim in a recent measurement.
We present the inclusive invariant-mass, transverse momentum and rapidity distributions of dielectrons (e$^{+}$e$^{-}$ pairs) in p+p interactions at 3.5 GeV beam kinetic energy. In the vector-meson mass region, a distinct peak corresponding to direct $omega$ decays is reconstructed with 2% mass resolution. The data is compared to predictions from three model calculations. Due to the large acceptance of the HADES apparatus for $e^{+}e^{-}$ invariant masses above 0.2 GeV/$c^{2}$ and for transverse pair momenta p$_{t}$ $ <$ 1 GeV/$c$, acceptance corrections are to a large extent model independent. This allows us to extract from dielectron data for the first time at this energy the inclusive production cross sections for light vector mesons. Inclusive production cross sections for $pi^o$ and $eta$ mesons are also reported. The obtained results will serve as an important reference for the study of vector meson production in proton-nucleus and heavy-ion collisions. Furthermore, using this data, an improved value for the upper bound of the branching ratio for direct $eta$ decays into the electron-positron channel is obtained.
The E12-14-012 experiment, performed in Jefferson Lab Hall A, has collected exclusive electron-scattering data (e,e$^prime$p) in parallel kinematics using natural argon and natural titanium targets. Here, we report the first results of the analysis of the data set corresponding to beam energy of 2,222 MeV, electron scattering angle 21.5 deg, and proton emission angle -50 deg. The differential cross sections, measured with $sim$4% uncertainty, have been studied as a function of missing energy and missing momentum, and compared to the results of Monte Carlo simulations, obtained from a model based on the Distorted Wave Impulse Approximation.
In explosive stellar environments like supernovae, the temperatures are high enough for the production of heavy neutron-deficient nuclei, the socalled p-nuclei. Up to now, the knowledge of the reaction rates of p-nuclei is based on theoretical parameterizations using statistical model calculations. At the bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ Dresden-Rossendorf, we aim to measure the photodisintegration rates of heavy nuclei experimentally. Photoactivation measurements on the astrophysically relevant p-nuclei 92Mo and 144Sm have been performed with bremsstrahlung end-point energies from 10.0 to 16.5 MeV. First experiments on the short-lived decays following the reaction 144Sm(gamma,n) are carried out using a pneumatic delivery system for rapid transport of activated samples. The activation yields are compared with calculations using cross sections from recent Hauser-Feshbach models.
The influence of short-range correlations (SRC) on the triple-coincidence (e,e$$pp) reactions is studied. The non-relativistic model uses a mean-field potential to account for the distortions that the escaping particles undergo. Apart from the SRC, that are implemented through a Jastrow ansatz with a realistic correlation function, we incorporate the contribution from pion exchange and intermediate $Delta _{33}$ currents. The (e,e$$pp) cross sections are predicted to exhibit a sizeable sensitivity to the SRC. The contribution from the two-nucleon breakup channel to the semi-exclusive $^{12}$C(e,e$$p) cross section is calculated in the kinematics of a recent NIKHEF-K experiment. In the semi-exclusive channel, a selective sensitivity in terms of the missing energy and momentum to the SRC is found.
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