Evidence of a dibaryon spectrum in coherent π0π0d photoproduction at forward deuteron angles

The coherent reaction, was studied with the BGOOD experiment at ELSA from threshold to a centre-of-mass energy of 2850 MeV. A full kinematic reconstruction was made, with final state deuterons identified in the forward spectrometer and decays in the central BGO Rugby Ball. The strength of the differential cross section exceeds what can be described by models of coherent photoproduction and instead supports the three isoscalar dibaryon candidates reported by the ELPH collaboration at 2.38, 2.47 and 2.63 GeV/c2. A low mass enhancement in the invariant mass is also observed at the ⁎ centre-of-mass energy which is consistent with the ABC effect. At higher centre-of-mass energies, a narrow peak in the invariant mass at 2114 MeV/c2 with a width of 20 MeV/c2 supports a sequential two-dibaryon decay mechanism

Measurement of the γ n → K0 0 differential cross section over the K∗ threshold

The differential cross section for the quasi-free photoproduction reaction gamma(n)-> K-0 Sigma(0) was measured at BGOOD at ELSA from threshold to a centre-of-mass energy of 2400 MeV. Close to threshold the results are consistent with existing data and are in agreement with partial wave analysis solutions over the full measured energy range, with a large coupling to the Delta(1900)1/2(-) evident. This is the first dataset covering the K* threshold region, where there are model predictions of dynamically generated vector meson-baryon resonance contributions

Observation of a cusp-like structure in the γp → K+Σ0 cross section at forward angles and low momentum transfer

The gamma+p->K+ + Sigma0 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 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

Measurement of the γn→K0Σ0\gamma n\rightarrow K^0\Sigma^0 differential cross section over the K∗K^* threshold

The differential cross section for the quasi-free photoproduction reaction $\gamma n\rightarrow K^0\Sigma^0$ was measured at BGOOD at ELSA from threshold to a center-of-mass energy of 2400 MeV. An increase in the cross section is observed at forward angles above 2000 MeV. The available statistics prevent an accurate description of this behavior, however it appears consistent with models describing a resonance of dynamically generated vector meson-baryon states, where an equivalent model predicted the $P_C$ states observed at LHCb. If proven correct, this could indicate parallels between the strange and charmed quark sectors.Comment: 6 pages, 8 figure

K+Λ photoproduction at forward angles and low momentum transfer

gamma p -> K+Lambda 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