We calculate total photon-nucleus and electron-nucleus cross sections γA → X, eA → e ′ X and several cross sections on pion and eta production in nuclei in the energy regime between the first and the third resonance region for photon virtualities Q 2 ≤ 1.0 GeV 2 within a semi-classical BUU transport model. In both cases we discuss the varying influence of several medium modifications on the cross sections for different values of Q 2 .
Abstract. Photoproduction of neutral pions from nuclei (carbon, calcium, niobium, lead) has been studied for incident photon energies from 200 MeV to 800 MeV with the TAPS detector using the Glasgow photon tagging spectrometer at the Mainz MAMI accelerator. Data were obtained for the inclusive photoproduction of neutral pions and the partial channels of quasifree single π 0 , double π 0 , and π 0 π ± photoproduction. They have been analyzed in terms of the in-medium behavior of nucleon resonances and the pion -nucleus interaction. They are compared to earlier measurements from the deuteron and to the predictions of a Boltzmann-Uehling-Uhlenbeck (BUU) transport model for photon induced pion production from nuclei.
The nucleon spectral function in infinite nuclear matter is calculated in a quantum transport theoretical approach. Exploiting the known relation between collision rates and correlation functions the spectral function is derived self-consistently. By re-inserting the spectral functions into the collision integrals the description of hard processes from the high-momentum components of wave functions and interactions is improved iteratively until convergence is achieved. The momentum and energy distributions and the nuclear matter occupation probabilities are in very good agreement with the results obtained from many-body theory.A longstanding problem of nuclear many-body theory is the question to what extent short-range correlations are contributing to the properties of nuclear matter. While the bulk properties of nuclear matter are mainly affected by long-range mean-field dynamics, the picture, however, changes if nuclei are probed at large energy and momentum transfer. The spectral functions, * Work supported by BMBF, DFG and GSI Darmstadt
Abstract. Recent experimental results for meson photoproduction from nuclei obtained with TAPS at MAMI are analyzed in view of the suppression of the second nucleon resonance region in total photoabsorption. The cross sections can be split into a component from the low density surface region of nuclei and a component which scales more like the nuclear volume. The energy dependence of the surface component is similar to the deuteron cross section, it shows a clear signal for the second resonance peak assigned to the excitation of the P11(1440), D13(1520), and S11(1535). The volume component behaves differently, it is lacking the second resonance peak and shows an enhancement at intermediate photon energies.
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