Yusuke Tsuchikawa

An event mixing technique for Bose-Einstein correlations of two pions in photoproduction around 1 GeV

We have developed an event mixing technique to observe Bose-Einstein correlations (BEC) between two identical neutral pions produced in photo-induced reactions in the non-perturbative QCD energy region. It is found that the missing-mass consistency cut and the pion-energy cut are essential for the event mixing method to effectively extract BEC observables. A Monte Carlo (MC) simulation is used to validate these constraints and confirms the efficiency of this method. Our work paves the way for similar BEC studies at lower energies where the multiplicity of emitted bosons is limited.

Development of a high-intensity photon-beam profile monitor

Several beam-profile monitors have been developed for high-energy photon beamlines at the Research Center for Electron Photon Science, Tohoku University, Japan. The position of the photon converted into an electron-positron pair in a metal plate is measured in these monitors. In the current monitor, two layers of 16 scintillating-fiber hodoscopes with a cross section of a 3-mm square have been adopted for the position measurement. The effective area is a 48 mm square. Events in which charged particles are produced upstream are rejected with a charge veto plastic scintillator placed in front of the plate, and pair-production events are identified with a trigger plastic scintillator placed behind the plate. The position is determined by a logic circuit with a field-programmable gate array. The dead time for processing an event is several tens of ns, and a high data acquisition efficiency can be achieved with these monitors for high-intensity photon beams (approximately 400 MHz). In the new developing monitor, the scintillating-fiber hodoscopes are planned to be replaced with a multi-anode metal-packaged photomultiplier tube. The secondary emission electrons produced at the photoelectric surface by the electron-positron pair are utilized for the position measurement. In this contribution, the overview of the developed monitor and prospects of the developing monitor will be discussed.