This work measured dσ/dΩ for neutral kaon photoproduction reactions from threshold up to a c.m. energy of 1855MeV, focussing specifically on the γp→K0Σ+, γn→K0Λ, and γn→K0Σ0 reactions. Our results ...for γn→K0Σ0 are the first-ever measurements for that reaction. These data will provide insight into the properties of N* resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the πN channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.
Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz in the three isospin channels gammaover -->p-->pi(+)pi(0)n, gammaover -->p-->pi(0)pi(0)p, and gammaover ...-->p-->pi(+)pi(-)p. The circularly polarized photons, produced from bremsstrahlung of longitudinally polarized electrons, were tagged with the Glasgow magnetic spectrometer. Charged pions and the decay photons of pi(0) mesons were detected in a 4pi electromagnetic calorimeter which combined the Crystal Ball detector with the TAPS detector. The precisely measured asymmetries are very sensitive to details of the production processes and are thus key observables in the modeling of the reaction dynamics.
High-statistics measurements of the photon asymmetry Σ for the $\overrightarrow{\gamma}p \rightarrow \pi^{0} p$ 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 resulting measurements 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, $\check{Σ}$ (= σ0Σ), and perform a moment analysis. Comparison with calculations from the Bonn-Gatchina model shows that the precision of the data is good enough to further constrain the higher partial waves, and there is an indication of interference between the very small F-waves and the N(1520)3/2- and N(1535)1/2- resonances.
The in-medium properties of the
ω
meson were investigated at the MAMI-C electron accelerator using the Crystal Ball/TAPS detector system to identify
ω
mesons through their
ω
→
π
0
γ
decay channel. ...Two solid targets (C, Nb) and a LH
2
target as a reference have been used. In the energy range 900 to 1300 MeV the
ω
lineshapes for the different nuclei are compared and a broadening of the
ω
signal for the niobium target is observed in comparison to the liquid-hydrogen target. In a second analysis the
ω
momentum distributions for the solid targets are determined for 50 MeV/
c
wide bins. For both analyses a comparison to transport calculations shows that the data are consistent with an in-medium modification by collisional broadening, as observed by transparency ratio measurements.
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