The BGOOD experimental setup at ELSA Alef, S.; Bauer, P.; Bayadilov, D. ...
The European physical journal. A, Hadrons and nuclei,
04/2020, Letnik:
56, Številka:
4
Journal Article
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The BGOOD experiment at the ELSA facility in Bonn has been commissioned within the framework of an international collaboration. The experiment pursues a systematic investigation of non-strange and ...strange meson photoproduction, in particular
t
-channel processes at low momentum transfer. The setup uniquely combines a central almost
4
π
acceptance BGO crystal calorimeter with a large aperture forward magnetic spectrometer providing excellent detection of both neutral and charged particles, complementary to other setups such as Crystal Barrel, Crystal Ball, LEPS and CLAS.
The helicity dependence of all single- and double-pion photoproduction channels on the proton has been measured for the first time at incident photon energies from 200 to 800 MeV. The measurement at ...the tagged photon beam facility of the MAMI accelerator in Mainz used the large acceptance detector DAPHNE and a frozen-spin target.
This completely new and up to now inaccessible observable represents a very sensitive tool to study baryon resonances since the smaller resonant multipoles can be accessed via the interference with the dominant ones.
The most recent results from the Mainz experiment are presented, with a particular emphasis on the second resonance region, where there are clear systematic discrepancies with the existing multipole analyses. In this region, double polarization data are mostly sensitive to the properties of the
D
13(1520) resonance and can be used to determine its properties much more accurately than in previous measurements.
.
The photoproduction of
and
mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9GeV at the electron accelerator ELSA. ...The mesons have been identified via the
and
decays, respectively, registered with the CBELSA/TAPS detector system. From the measured meson momentum distributions the momentum dependence of the transparency ratio has been determined for both mesons. Within a Glauber analysis the in-medium
and
widths and the corresponding absorption cross sections have been deduced as a function of the meson momentum. The results are compared to recent theoretical predictions for the in-medium
width and
-N absorption cross sections. The energy dependence of the imaginary part of the
- and
-nucleus optical potential has been extracted. The finer binning of the present data compared to the existing data allows a more reliable extrapolation towards the production threshold. The modulus of the imaginary part of the
-nucleus potential is found to be about three times smaller than recently determined values of the real part of the
-nucleus potential, which makes the
meson a suitable candidate for the search for meson-nucleus bound states. For the
meson, the modulus of the imaginary part near threshold is comparable to the modulus of the real part of the potential. As a consequence, only broad structures can be expected, which makes the observation of
mesic states very difficult experimentally.
A liquid hydrogen target for the MUSE experiment at PSI Roy, P.; Corsetti, S.; Dimond, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2020, Letnik:
949, Številka:
C
Journal Article
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A 280ml liquid hydrogen target has been constructed and tested for the MUSE experiment at PSI to investigate the proton charge radius via simultaneous measurement of elastic muon–proton and elastic ...electron–proton scattering. To control systematic uncertainties at a sub-percent level, strong constraints were put on the amount of material surrounding the target and on its temperature stability. The target system was successfully operated during a commissioning run at PSI at the end of 2018. The target temperature was stable at the 0.01K level. This suggests a density stability at the 0.02% level, which is about a factor of ten better than required.
The polarization observables T,E,P,H, and G in photoproduction of η mesons off protons are measured for photon energies from threshold to W=2400 MeV (T), 2280 MeV (E), 1620 MeV (P,H), or 1820 MeV ...(G), covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, JüBo, and BnGa partial-wave analyses. A refit within the BnGa approach including further data yields precise branching ratios for the Nη decay of nucleon resonances. A Nη-branching ratio of 0.33±0.04 for N(1650)1/2− is found, which reduces the large and controversially discussed Nη-branching ratio difference of the two lowest mass JP=1/2−-resonances significantly.
A liquid hydrogen target for the MUSE experiment at PSI Roy, P.; Corsetti, S.; Dimond, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2020, Letnik:
949
Journal Article
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