K. Nawa

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.

N* (1670) observed at LNS, Sendai

A resonance-like structure has been observed in the total cross section for the γd → ηnp reaction at E γ ∼ 1.02 GeV. The experiment was conducted at Laboratory of Nuclear Science, Tohoku University, by utilizing a tagged photon beam provided with an internal radiator in a 1.2 GeV electron synchrotron. A solid deuterium target was employed as well as a solid hydrogen target to extract information on the process γn → ηn. A clear bump has been observed in the total cross section for the γn’ → ηn reactio where n’ means a neutron in Fermi motion. A simple analysis gives the position of about 1670 MeV and the width of less than 40 MeV for the bump, respectively, taking into account the Fermi motion. There is no bump structure observed, in contrast, in the γp→ ηp process at the same energy region. The U-spin conservation may naturally account for this phenomenon, if the bump is an indication of a hidden-strangeness pentaquark baryon N 5(1670) in the anti-decuplet state.