A large mass reduction of the η′(958) in nuclei is expected in several theoretical models. If there is large mass reduction, an η′ meson and a nucleus can form a bound state. We investigated the η′-nucleus system in the LEPS2/BGOegg experiment. To search for the η′-nucleus bound state, we carried out the missing mass spectroscopy of the 12C(γ,p) reaction. To suppress background events from...
Origin of hadron masses have wide interests in the field of nuclear physics. Light quarks, such as up and down quarks, only have “bare” mass of a few MeV/c^2. A proton and a neutron, which contains only three quarks, have mass of ~1 GeV/c^2. This difference between quark mass and hadron mass can be theoretically explained as dynamical generations of hadron mass by a spontaneous breaking of a...
In this talk I will present a theoretical study of the γd→π0ηd reaction and show that the observed shift of the peaks of the π0d, ηd invariant mass distributions with respect to the phase space distributions are related to the dynamics of the γp→π0ηp.
In a recent work, we have studied the decay properties of N(1895), which was found to arise from meson-baryon interactions in an earlier work. We investigate the decays to different meson-baryon systems and to final states involving \Lambda(1405) and a proposed \Sigma(1400). In this talk, I will show that the width of N^(1895) can get an important contributions from the decay to light hyperon...
The excitation spectrum of the nucleon is an important testing ground for quantum chromodynamics in the regime where it cannot be treated perturbatively. During the last two decades much progress has been made on the theory side, e.g. lattice gauge methods and in experiments, particularly using energy tagged photon beams at electron accelerators, which has now reached a state where not only...
Photon induced π0π±-pairs production from quasi-free nucleons bound in the deuteron has been investigated in view of the helicity dependence of those two reactions. Measurements with a liquid deuterium target were used to extract the unpolarized cross sections for protons and neutrons. A deuterated, longitudinally polarized butanol target together with a circularly polarized photon beam was...
