Linearly polarized photons at MAMI (Mainz)

Lohmann, D.; Peise, J.; Ahrens, J.; Anthony, I.; Arends, H. J.; Beck, R.; Crawford, Ronald L.; Hünger, A.; Kaiser, K.-H.; Kellie, J.D.; Klümper, Ch.; Krahn, P.; Kraus, Alfred A.; Ludwig, U.; Schumacher, M.; Selke, O.; Schmitz, M.; Schneider, M.; Wissmann, F.; Wolf, S.

doi:10.1016/0168-9002(94)90230-5

Cited by 61 publications

(26 citation statements)

References 28 publications

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“…Brookhaven [50], Lund [51,52], Mainz [53,54], Saskatoon [55] -where experiments on Compton scattering by nuclei are carried out. Back scattering of laser light [50] and coherent bremsstrahlung from diamond crystals [56][57][58] are also efficient sources of linearly polarized photons. At low energies (5-100 MeV) also the method of off-axis tagging [33,59] leads to reasonable degrees of linear polarization.…”

Section: Nuclear Compton Scattering Experiments From the Mid-1970th Tmentioning

confidence: 99%

Compton scattering by nuclei

et al. 2000

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The concept of Compton scattering by even-even nuclei from giant-resonance to nucleon-resonance energies and the status of experimental and theoretical researches in this field are outlined. The description of Compton scattering by nuclei starts from different complementary approaches, namely from second-order S-matrix and from dispersion theories. Making use of these, it is possible to incorporate into the predicted nuclear scattering amplitudes all the information available from other channels, viz. photon-nucleon and photon-meson channels, and to efficiently make use of models of the nucleon, the nucleus and the nucleon-nucleon interaction. The total photoabsorption cross section constrains the nuclear scattering amplitude in the forward direction. The specific information obtained from Compton scattering therefore stems from the angular dependence of the nuclear scattering amplitude, providing detailed insight into the dynamics of the nuclear and nucleon degrees of freedom and into the interplay between them. Nuclear Compton scattering in the giant-resonance energy-region provides information on the dynamical properties of the in-medium mass of the nucleon. Most prominently, the electromagnetic polarizabilities of the nucleon in the nuclear medium can be extracted from nuclear Compton scattering data obtained in the quasideuteron energy-region. In our description of this latter process special emphasis is laid upon the exploration of many-body and two-body effects entering into the nuclear dynamics. Recent results are presented for two-body effects due to the mesonic seagull amplitude and due to the excitation of nucleon internal degrees of freedom accompanied by meson exchanges. Due to these studies the inmedium electromagnetic polarizabilities are by now well understood, whereas the understanding of nuclear Compton scattering in the ∆-resonance range is only at the beginning. Furthermore, phenomenological methods how to include retardation effects in the scattering amplitude are discussed and compared with model predictions.

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Section: Nuclear Compton Scattering Experiments From the Mid-1970th Tmentioning

confidence: 99%

Compton scattering by nuclei

et al. 2000

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“…The linear polarization of the photons was produced from coherent bremsstrahlung [16,17], where the electron beam scatters coherently from a suitably aligned crystal radiator. A thin diamond crystal (30 μm), with low mosaic-structure, was used to minimize the energy smearing of the coherent spectrum arising from electron multiple scattering effects and crystal defects in the lattice [18].…”

Section: Methodsmentioning

confidence: 99%

Photon asymmetry measurements of $\overrightarrow{\gamma}p \rightarrow \pi^{0} p$ γ → p → π 0 p for $E_{\gamma}=$ E γ = 320-650 MeV

Gardner¹,

Howdle²,

Sikora³

et al. 2016

Eur. Phys. J. A

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Abstract. High-statistics measurements of the photon asymmetry Σ for the γp → π 0 p reaction have been made in the center-of-mass energy range W = 1214-1450 MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The results significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. We have also combined the photon asymmetry results with recent cross-section measurements from Mainz to calculate the profile functions,Σ (= σ 0Σ),

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“…A photon beam with strong linear polarisation can be produced using the technique of coherent bremsstrahlung [26,27] where the electron beam scatters coherently from a suitably aligned crystal radiator. A thin diamond crystal, with low mosaic structure, minimises the energy smearing of the coherent spectrum arising from electron multiple scattering effects and crystal defects in the lattice [28].…”

Section: Methodsmentioning

confidence: 99%

Measurements of 12C $(\vec{\gamma},pp)$ photon asymmetries for $E_{\gamma}=200$ –450 MeV

Robinson¹,

MacGregor²,

Annand³

et al. 2013

Eur. Phys. J. A

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Abstract. The12 C( 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 E γ 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.

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Linearly polarized photons at MAMI (Mainz)

Cited by 61 publications

References 28 publications

Compton scattering by nuclei

Compton scattering by nuclei

Photon asymmetry measurements of $\overrightarrow{\gamma}p \rightarrow \pi^{0} p$ γ → p → π 0 p for $E_{\gamma}=$ E γ = 320-650 MeV

Measurements of 12C $(\vec{\gamma},pp)$ photon asymmetries for $E_{\gamma}=200$ –450 MeV

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