Strangeness Photoproduction at the BGO-OD experiment

TL;DR

The BGO-OD experiment investigates nucleon excitation and strangeness photoproduction using a specialized detector setup, revealing structures in reaction channels that suggest meson-baryon generated states and potential links to pentaquark phenomena.

Contribution

This work provides new experimental insights into low momentum transfer strangeness photoproduction, highlighting structures that may indicate molecular states and connections to pentaquark models.

Findings

Observation of a cusp-like structure at W=1900 MeV in K+Σ0 photoproduction

Identification of line shapes and differential cross sections for K+Λ(1405) reactions

Detection of a peak in K0SΣ0 photoproduction consistent with meson-baryon states

Abstract

The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. 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 low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. First key results at low $t$ indicate a cusp-like structure in $K^+\Sigma^0$ photoproduction at $W = 1900$\,MeV, line shapes and differential cross sections for $K^+\Lambda$(1405)$\rightarrow K^+\Sigma^0\pi^0$, and a peak structure in $K^0_S\Sigma^0$ photoproduction. The peak in the $K^0_S\Sigma^0$ channel appears consistent with meson-baryon generated states, where equivalent models have been used to describe the $P_C$ pentaquark candidates in the heavy charmed quark sector.