Search for the pentaquark states in lepton-nucleon scattering at HERMES

Abstract

A narrow baryon state has been found in the channel pK_S -> p pi+ pi- of quasi-real photoproduction on a deuterium target at the HERMES experiment. Its mass is 1528+-2.6+-2.1 MeV and its width is somewhat larger than the experimental resolution of 4.3-6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Theta+ pentaquark baryon. The work describes the methodsof the state extraction from the HERMES data and studies of its decay kinematics. The second part of the work describes designing of readout electronics forScintillating Fiber Tracker in Recoil Detector project at HERMES. The detectoris aimed to identify recoiled protons from Deeply Virtual Compton Scattering(DVCS) process, which is an option to extract Generalized Parton Functions ofthe nucleon. Due to enlarged acceptance of HERMES spectrometer by RecoilDetector and its particle identification capability, the designed device isable significantly contribute to search for pentaquark state.