Study of in medium mass modification for the phi meson using phi meson bound state in nucleus
大西 宏明
理化学研究所岩崎先端中間子研究室
日時：2009年06月22日（月） 16:00-
場所：大学院講義室（総合研究棟7階745号室）
A search for the $\phi$-meson bound state itself is already quiteinteresting, although it seems to be natural that the $\phi$ formsa stable nuclear bound state. Compared to other vector-mesonstudies, the $\phi$ is quite interesting due to its narrow width.Since the $\phi$ barely interacts with surrounding nucleons, it isnatural to have a narrow width even in nuclei. In fact, the widthbroadening in nuclear media is reported to be only 3.4 times thatof free space. This fact makes the discrete peak observation inthe missing mass feasible and allows simple analysis of themass shift from the systematic study of the binding energies overseveral nuclei.A systematic study over several nuclear targets will yield aunique, definitive and precise determination of the in-mediummass modification of the vector meson $\phi(s\overline{s})$.Recently, we proposed new idea of the experiment to studyin-medium mass modification of the $\phi$ meson via theformation of $\phi$ meson bound state to J-PARC.In this presentation, we will demonstrate that a completelybackground-free missing-mass spectrum can be obtainedefficiently by $(\overline{p}, \phi)$ spectroscopy together withthe $K^+\Lambda$ tagging, using the primary reaction channel$\overline{p} p \rightarrow \phi \phi$. From both missing massand invariant mass study of the sub-threshold energy region,one can independently deduce the mass shift information.