K0SΣ0 photoproduction at the BGO-OD experiment

Katrin Kohl ,Patrick Bauer,Christian Tillmanns,Francesco Oliver,A Braghieri ,A Lapik ,A Fantini ,V Lisin ,D V Novinsky ,P Pedroni ,D Moricciani ,O Freyermuth ,M Romaniuk ,V V Sumachev ,V Nedorezov ,D Elsner ,A Polonski ,G Scheluchin ,P L Cole ,A Gridnev ,B Reitz ,В И Тараканов ,S Alef ,R Di Salvo ,J Hannappel ,G Mandaglio ,Thomas Jude ,P Levi Sandri ,N Kozlenko ,R Beck ,H Schmieden ,R Messi ,D Hammann

doi:10.1051/epjconf/202024101009

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 via meson photoproduction. The setup with a BGO calorimeter surrounding the target and an open dipole spectrometer covering the for ward region is ideally suited for investigating low momentum transfer processes, in particular in strangeness photoproduction. The associated photoproduction of K0S and hyperons is essential to understand the role of K* exchange mech anisms. A cusp-like structure observed in the yp → K0SΣ+ reaction at the K* threshold is described by models including dynamically generated resonances from vector meson-baryon interactions. Such interactions are pre dicted to give a peak like structure in K0SΣ0 photoproduction off the neutron. A very preliminary cross section is determined and compared to the prediction, the results appear to support the model

Highlights

IntroductionThe cusp-like structure observed in the γp → K0Σ+ differential cross section by Ewald et al [1] is not described in previous isobar and PWA models, for example SAID [2] and K-MAID [3]
A cusp-like structure observed in the γp → KS0 Σ+ reaction at the K∗ threshold is described by models including dynamically generated resonances from vector meson-baryon interactions
The cusp-like structure observed in the γp → K0Σ+ differential cross section by Ewald et al [1] is not described in previous isobar and PWA models, for example SAID [2] and K-MAID [3]

Summary

Introduction

The cusp-like structure observed in the γp → K0Σ+ differential cross section by Ewald et al [1] is not described in previous isobar and PWA models, for example SAID [2] and K-MAID [3]. The photon beam impinges on a fixed target, usually liquid hydrogen or deuterium This is surrounded by a Multi-Wire-Proportional-Chamber for tracking, a scintillator barrel to provide charge information and an electromagnetic calorimeter made from BGO. This central detector is ideally suited for photon detection, and able to detect other charged or neutral particles. To determine a cross section of γn → K0Σ0 the decay channel K0Σ0 → π0π0Λγ → 5γΛ is identified, by requesting exactly five neutral and any number of charged particle. 2π0 invariant mass spectrum before and after selecting Σ0 decay photon. The Root tool Roofit[8] is used to determine the number of signal events from the 2π0 invariant mass spectrum (section 3.3)

Tagging Σ0 decay photon

Proton contamination

Fitting to data

Findings

Conclusion