THE BGO-OD EXPERIMENT AT ELSA

S Friedrick,T Rostomyan,D Moricciani,H Dutz,K Koop,O Jahn,J Hannappel,P Levi Sandri,R Joosten,R Beck,H Schmieden,V De Leo,D Elsner,S Goertz,C Schaerf,B Girolami,P Pedroni,G Giardina,R Messi,A Fantini,E Gutz,G Gervino,V Vegna,V Tarakonov,A Bella,J Bieling,V Metag,A Braglieri,D Noviskiy,D Hammann,F Ghio,R Di Salvo,M Romaniuk,S Böse,B Bantes,R Jahn,B Krusche,A Ignatov,Dirk Walther ,Kai-Thomas Brinkmann ,D Burdeinyi ,M Nanova,V V Sumachev ,T Frese,F Curciarello,Thomas Jude ,D Bayadilov,H.-G Zaunick,F Messi,D I Glazier ,I Lopatin,T Zimmermann,A Lapik,A Gridnev,P Vlasov,F Frommberger,G Mandaglio,D P Watts ,M Becker,Frank Klein ,V.b Ganenko ,V Nedorezov,W Hillert

doi:10.1142/s2010194514600933

Abstract

Meson photoproduction is a key tool for the experimental investigation of the nucleon excitation spectrum. To disentangle the specific couplings of resonances, in addition to the rather well measured pion and eta photoproduction channels it is mandatory to obtain information on channels involving strange and vector mesons and higher mass pseudoscalar mesons, and the associated multi-particle final states with both charged and neutral particles. In this respect, the new BGO-OD experiment at the ELSA accelerator of the University of Bonn's Physikalisches Institut provides unique instrumentation. We describe the experiment, present its status and the initial program of measurements.

Highlights

The experimental study of the nucleon excited states through photoproduction requires both high intensity polarizable beams and large solid-angle hermetic detectors
The calorimeter is combined with two multi-wire proportional chambers (MWPC) for inner tracking and a plastic scintillator barrel for particle identification through the measurement of dE/dx
The scintillator barrel inside the BGO is located between the crystals and the inner tracking detector (MWPC)

Summary

Introduction

The experimental study of the nucleon excited states through photoproduction requires both high intensity polarizable beams and large solid-angle hermetic detectors. Large solid angle detectors can, in turn, be optimized for the measurement of charged particles (e.g. CLAS detector at Jefferson Lab.1) or of neutral (photons) particles (e.g. CB-ELSA detector[2]). The detector will provide excellent energy resolution and detection efficiency for neutrals by exploiting the features of the BGO Rugby Ball calorimeter, coupled with the Open Dipole spectrometer for charged particles in the forward direction. This way, mixed-charge final states will be accurately measured, allowing the study of specific final states that are presently poorly known.

Photon Beam

Detector

Present Status and Initial Experimental Program