Speaker
Description
At SPring-8 LEPS2 beamline, a linearly polarized photon beam is available in the tagged energy range of 1.3–2.4 GeV. The first stage of LEPS2 project was carried out using an experimental setup with a large acceptance calorimeter, called BGOegg, which had the world’s best resolution in the energy range around 1 GeV. So far, we have intensively studied for the origin of hadron mass via $\eta^\prime$ meson photoproduction inside a nucleus, where the spontaneous breaking of chiral symmetry is expected to be partially restored. A summary of our analyses will be shown including a direct spectral measurement of in-medium $\eta^\prime$ mass and a search for $\eta^\prime$ mesic nuclei. In addition, an on-going experiment with an upgraded setup will be discussed as a second-stage study for the in-medium $\eta^\prime$ mass.
Other physics subjects with the use of the BGOegg calorimeter will be also overviewed, containing the investigation of high mass and high spin baryon resonances via photoproduction of $\pi^0$, $\eta$, $\omega$, and $\eta^\prime$ mesons from a liquid hydrogen target. Recently, we have succeeded in observing the photoproduction of a $f_0$(980) meson decaying into $\pi^0 \pi^0$, for the first time. The measured differential cross sections and photon beam asymmetries provide useful information about the $f_0$(980) structure, which may be an exotic non-$q\bar{q}$ state.
In parallel to the second-stage experiment with the BGOegg calorimeter, we now operate a different experimental setup with a $4\pi$ charged-particle spectrometer installed inside a large volume solenoidal magnet. Recent status and future prospect will be given for a variety of subjects in the LEPS2 project.
| Collaboration | SPring-8 LEPS2 |
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