The helicity dependence of the total cross section for the γ→p→→nπ+π0 reaction has been measured for the first time at incident photon energies from 400 to 800 MeV. The measurement was performed with ...the large acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. This channel is found to be excited predominantly when the photon and proton have a parallel spin orientation, due to the intermediate production of the D13 resonance.
The ( γ , p d ) reaction in 12 C McAllister, S. J.; McGeorge, J. C.; MacGregor, I. J. D. ...
Physical review. C, Nuclear physics,
9/1999, Letnik:
60, Številka:
4
Journal Article
Eur. Phys. J. A29 261-270 (2006) This paper reports on the first measurement of the ^16O(e,e'pn)^14N reaction.
Data were measured in kinematics centred on a super-parallel geometry at energy
and ...momentum transfers of 215 MeV and 316 MeV/c. The experimental resolution
was sufficient to distinguish groups of states in the residual nucleus but not
good enough to separate individual states. The data show a strong dependence on
missing momentum and this dependence appears to be different for two groups of
states in the residual nucleus. Theoretical calculations of the reaction using
the Pavia code do not reproduce the shape or the magnitude of the data.
The helicity dependence of the (γ) over right arrow(p) over right arrow -->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, ...performed at the Mainz microtron MAMI, used a 4pi -detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D-13(1520) resonance and are used to determine its helicity amplitudes.
A high-quality double-polarization data set for the helicity dependence of the total and differential cross-sections for both gammap --> Npi channels in the Delta region has been obtained in the ...framework of the GDH experiment. The experiment, performed at the Mainz microtron MAMI, used a 4pi detection system, a circularly polarized photon beam, and a longitudinally polarized frozen-spin target. These data are included in the database to perform a multipole analysis to determine the properties of the Delta(1232)-resonance. For the resonant Delta(1232) multipoles we find a very good agreement with previous analyses, while the nonresonant ones show significant deviations.
The dynamics of the \(\eta\to 3\pi^0\) decay have been studied with the Crystal Ball multiphoton spectrometer and the TAPS calorimeter. Bremsstrahlung photons produced by the 1.5-GeV electron beam of ...the Mainz microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for \(\eta\)-meson production. The analysis of \(3 \times 10^6\) \(\gamma p \to \eta p \to 3\pi^0 p \to 6\gamma p\) events yields the value \(\alpha=-0.032\pm0.003\) for the \(\eta\to 3\pi^0\) slope parameter, which agrees with the majority of recent experimental results and has the smallest uncertainty. The \(\pi^0\pi^0\) invariant-mass spectrum was investigated for the occurrence of a cusplike structure in the vicinity of the \(\pi^+\pi^-\) threshold. The observed effect is small and does not affect our measured value for the slope parameter.
Eur.Phys.J. A22 (2004) 277-291 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 pi0, double pi0, and
pi0pi+/- 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.
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