M. Mirazita

Extension of the intranuclear cascade model for photonuclear reactions at energies up to 10 GeV

Abstract The intranuclear cascade (INC) model for photonuclear reactions has been extended at energies up to 10 GeV. To this end a phenomenological method for exclusive description of the elementary γN-interaction has been developed taking into account both the resonance contribution from the two-body channels γN → πB ∗ and γN → M ∗ N ( B ∗ and M ∗ being baryon and meson resonances) and the non-resonant statistical contribution from multibody channels γN → iπN (2 ⩽ i ⩽ 8). This method well describes a wide range of γN data up to Eγ ∼ 10 GeV. The INC model takes into account rescattering and absorption in a nucleus of pions, nucleons, and η-, ϱ-, ω-mesons generated in the γN-interaction. The evaporation, fission and multifragmentation of highly excited residual nucleus have also been taken into account. As a result of the Monte Carlo simulation an event of γA-reaction is generated which contains mesons, nucleons, nuclear fragments, fission fragments and final nuclide. The model well describes the available data on meson production and proton emission obtained with quasi-monochromatic photons.

Absolute measurement of the total photoabsorption cross section for carbon in the nucleon resonance region

Abstract We present the results of an absolute measurement of the total nuclear photoabsorption cross section for carbon in the higher nucleon resonance region. In the Δ region our results agree with existing data, while at higher energies they show a damping in the excitation of the higher nucleon resonances, clearly seen in the photon absorption on proton and deutron.

Photoabsorption on nuclei in the energy range 0.5-2.6 GeV

The energy and nuclear mass dependences of the total hadronic cross section in the energy range 0.5-2.6 GeV have been measured at Bonn using the SAPHIR tagged photon beam. The measurement, performed on C, Al, Cu, Sn and Pb, provides the first photoabsorption data in the region 1.2-1.7 GeV. The results show a significant reduction of the photoabsorption strength on the bound nucleon compared to the free nucleon case in the whole energy region. Above 1.2 GeV this reduction decreases with the nuclear density and can be interpreted as a signature of a low energy onset of the shadowing effect.

Complete angular distribution measurements of two-body deuteron photodisintegration between 0.5 and 3 GeV

Nearly complete angular distributions of the two-body deuteron photodisintegration differential cross section have been measured using the CEBAF Large Acceptance Spectrometer detector and the tagged photon beam at the Thomas Jefferson National Accelerator Facility. The data cover photon energies between 0.5 and 3.0 GeV and center-of-mass proton scattering angles 10degrees-160degrees. The data show a persistent forward- backward angle asymmetry over the explored energy range, and are well described by the nonperturbative quark gluon string model.

Forward-backward angle asymmetry and polarization observables in high-energy deuteron photodisintegration

Abstract.Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. It is found that the forward-backward angle asymmetry predicted by the model is confirmed by the recent data at different photon energies from JLab. New calculations for polarization observables, the cross-section asymmetry

A Measurement of the Differential Cross Section for the Reaction

\Sigma

\gamma n \to \pi^-p

and the polarization transfer

from Deuterium

C_{z^{\prime}}

Studies of transverse momentum dependent parton distributions and Bessel weighting

, for photon energies

Total hadronic photoabsorption on carbon and lead in the shadowing threshold region

(1.2\mbox{--}6)