K+Λ(1405) photoproduction has been studied at the BGOOD experiment via the all neutral decay, Λ(1405)→Σ0π0. The unique BGOOD experimental setup allows both the cross section and Λ(1405) invariant ...mass distribution (line shape) to be measured over a broad K+ polar angle range, extending to extreme forward K+ angles unattainable at previous experiments.
Evidence is provided for the role of a triangle singularity driven by the N⁎(2030) resonance, which appears to contribute significantly to K+Λ(1405) photoproduction. This is observed in the integrated cross section which was determined with unprecedented energy resolution and supported by the angular distributions. The measured line shape is also in agreement with the previous results of CLAS and ANKE, and is consistent with two poles derived in χPT based models.
The positive-strangeness baryon resonance Θ+ is observed in photoproduction of the nK+K0s final state with the SAPHIR detector at the Bonn ELectron Stretcher Accelerator ELSA. It is seen as a peak in ...the nK+ invariant mass distribution with a 4.8σ confidence level. We find a mass MΘ+=1540±4±2 MeV and an upper limit of the width ΓΘ+<25 MeV at 90% c.l. The photoproduction cross section for K0Θ+ is in the order of 300 nb. From the absence of a signal in the pK+ invariant mass distribution in γp→pK+K− at the expected strength we conclude that the Θ+ must be isoscalar.
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
Recenzirano
Odprti dostop
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 γp→K+Σ0 differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the ...polar angle of the K+ in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900 MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.
γ
p
→
K
+
Λ
differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, ...utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The high statistics and forward angle acceptance enables the extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.
The first measurement is reported of the double-polarization observable G in the photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid ...angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand γp→pπ(0) as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N(1535) resonance with spin parity J(P)=1/2(-) and N(1520) with J(P)=3/2(-). In the third resonance region, where N(1680) with J(P)=5/2(+) production dominates, the new data are reasonably close to the predictions.
Low-energy photoproduction of $\omega$ -mesons Barth, J.; Braun, W.; Ernst, J. ...
The European physical journal. A, Hadrons and nuclei,
09/2003, Letnik:
18, Številka:
1
Journal Article
BGO-OD is a new meson photoproduction experiment at the ELSA facility of Bonn University. It aims at the investigation of non strange and strange baryon excitations, and is especially designed to be ...able to detect weekly bound meson-baryon type structures. The setup for the BGO-OD experiment is presented, the characteristics of the photon beam and the detector performances are shown and the initial experimental program is discussed.
Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W = 1748 MeV to W = 2045 MeV). The data ...cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη′ threshold Eγ = 1447 MeV (W = 1896 MeV). The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N (1895)1/2− nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.
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