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

Erratum to: Strangeness Photoproduction at the BGO-OD Experiment

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Photoproduction of K+ Δ(1405) → K+ π0 Σ0 extending to forward angles and low momentum transfer

K+ Lambda (1405) photoproduction has been studied at the BGOOD experiment via the all neutral decay, Lambda(1405)-> Sigma0 Pi0. The unique BGOOD experimental setup allows both the cross section and invariant mass Lamba(1405) 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+Lambda(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

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

Strangeness Photoproduction at the BGO-OD Experiment

BGO-OD is a newly commissioned experiment to investigate the internal structure of the nucleon, using an energy tagged bremsstrahlung photon beam at the ELSA electron facility. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating meson photoproduction. The extensive physics programme for open strangeness photoproduction is introduced, and preliminary analysis presented

Transverse low frequency broad-band impedance measurements in the CERN PS

The base-line scenario for the High-Luminosity LHC upgrade foresees an intensity increase delivered by the injectors. With its 53 years, the CERN PS would have to operate beyond the limit of its performance to match the future requirements. Beam instabilities driven by transverse impedance are an important issue for the operation with high intensity beams as for the high-brightness LHC beams. Measurements of transverse tune dependence with beam intensity were performed at injection kinetic energy 1.4 GeV and at LHC beam extraction momentum 26 GeV/c. This allows deducing the low frequency inductive broad-band impedance of the machine. Then an estimation of the real part of the impedance is made by the rise time measurement of a fast transverse instability at transition energy believed to be a TMCI type. Those are the first step towards a global machine impedance characterization in order to push forward the performances of the accelerator