Strangeness Photoproduction at the BGO-OD experiment

¹ Rheinische Friedrich-Willhelms-Universität Bonn, Physikalisches Institut, Nussallee 1-16, 53115 Bonn Germany
² Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, Nussallee 1-16 D-53115 Bonn Germany
³ Lamar University, Department of Physics, Beaumont, Texas 77710 USA
⁴ INFN Roma “Tor Vergata", Rome, Italy
⁵ Università di Roma “Tor Vergata", Via della Ricerca Scientifica 1, 00133 Rome Italy
⁶ INFN sezione di Roma La Sapienza, P.le Aldo Moro 2, 00185 Rome Italy
⁷ Istituto Superiore di Sanita, Viale Regina Elena 299, 00161 Rome Italy
⁸ Petersburg Nuclear Physics Institute, Gatchina, Leningrad District, 188300, Russia
⁹ Russian Academy of Sciences Institute for Nuclear Research, prospekt 60-letiya Oktyabrya 7a,, Moscow 117312 Russia
¹⁰ INFN - Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati Italy
¹¹ INFN sezione Catania, 95129, Catania Italy
¹² Universita degli Studi di Messina, Via Consolato del Mare 41, 98121 Messina Italy
¹³ INFN sezione di Pavia, Via Agostino Bassi, 6 - 27100 Pavia, Italy

^* Corresponding author: jude@physik.uni-bonn.de

Published online: 22 September 2020

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⁺Σ⁰ photoproduction at W = 1900 MeV, line shapes and differential cross sections for K⁺Λ(1405)→ K⁺Σ⁰π⁰, and a peak structure in K⁰_SΣ⁰ photoproduction. The peak in the K⁰_SΣ⁰ 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.