Measurements of 12C(→γ,pp) photon asymmetries for Eγ= 200–450 MeV

The 12C (→γ ,pp) reaction has been studied in the photon energy range 200-450 MeV at the Mainz microtron MAMI-C, where linearly polarised photons were energy-tagged using the Glasgow-Mainz Tagged Photon Spectrometer and protons were detected in the Crystal Ball detector. The photon asymmetry Σ has been measured over a wider Eγ range than previous measurements. The strongest asymmetries were found at low missing energies where direct emission of nucleon pairs is expected. Cuts on the difference in azimuthal angles of the two ejected protons increased the magnitude of the observed asymmetries. At low missing energies the Σ data exhibit a strong angular dependence, similar to deuteron photodisintegration

PiP - A large solid angle scintillation telescope for detecting protons and pions

A ~1 sr solid angle scintillation detector hodoscope for protons of up to ~280 MeV and positive pions of up to ~180 MeV energy has been developed for use in (gamma,pN), (gamma,p pi±) and (gamma,pi+ N) experiments with tagged photons. This paper reports the detailed design of the hodoscope and its performance for detecting protons and positive pions

Mechanisms in the ¹²C(γ,pn) and (γ,pp)reactions

¹²C(gamma,pn) and (gamma,pp) cross sections have been measured in kinematics which emphasize direct 2N knockout for E(gamma) =­ 120 - 400 MeV and theta(p) = ­23 - 152 deg. The cross sections for both reactions peak strongly in the Delta-resonance region. Theoretical calculations that account for the medium dependence of the Delta propagator predict a similar photon energy dependence to the data and describe the general trends of the measured (gamma,pp)/(gamma,pn) ratio. Both cross sections show strong angular dependence, and the large differences between the two channels indicate different microscopic reaction mechanisms

The (γ,pd) reaction in ¹²C

The ¹²C(gamma,pd) reaction has been studied for photon energies between 150 and 400 MeV using the Glasgow photon tagging spectrometer and plastic scintillator detectors at the Mainz MAMI electron accelerator. The overall energy resolution was ~6 MeV, sufficient to determine the initial shells of the emitted nucleons. The energy dependence of the cross section and the missing energy and recoil momentum spectra indicate that, for low residual excitation, the reaction proceeds through interaction with the three detected nucleons in a similar manner to the ³He(gamma,pd) reaction while the rest of the nucleus acts as a spectator

The ¹²C(gamma,NN) reaction studied over a wide kinematic range

The12C( gamma,np) and 12C( gamma,pp) reactions have been studied using the Glasgow photon tagging spectrometer at the Mainz MAMI electron microtron for E gamma = 150-700 MeV over a kinematic range which extends well beyond the approximately back-to-back detector arrangements of previous work. For 12C(gamma,np) the general trends of the missing energy distributions are reproduced over a wide range of kinematics and photon energies by the theory developed by the Valencia group. The corresponding 12C(gamma,PP) channel is overestimated by a factor of similar to 3. Detailed comparisons of the experimental data with a Monte Carlo simulation of the direct 2N knockout process provide the first evidence above the Delta resonance for direct 2N knockout and show that this process dominates the 12C(gamma,np) reaction at low missing energies up to E gamma similar to 700 MeV. The 12C(gamma,pp) reaction is somewhat less well described by the Monte Carlo simulation. A possible explanation of the observed discrepancies within a direct 2N framework is presented. At high recoil momenta both 2N reaction channels exhibit an excess yield compared to the Monte Carlo prediction of direct 2N knockout. The excess yield in this region is compared with the predicted effects of short-range correlations and with the predicted contributions due to other reaction mechanisms

Inter-professional roles and responsibilities in a clinical oncology service

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