Hadrons in Dense Matter

Abstract

Physical reason behind the mass-shift of vector mesons ($\rho$, $\omega$, $\varphi$) in nuclear matter is discussed in the Walecka model and in QCD sum rules. Using analytic formulas for the mass-shift valid at low densities, it is shown that the energy dependent part of the sels-energy (wave function renomalization) in medium is a main source for the negative mass-shift, while the energy independent part (the plasma frequency) has relatively a small effect. Future experiments in GSI (${\pi }^{-}+A\to X+\omega$ ) and KEK-PS ($p+A\to X+\varphi$ ) to detect the twin peak structure of vector mesons in $e^{+}{e}^{-}$ spectrum are reviewed. Also, it is proposed a new possible experiment using a $S(strangeness)=1$ vector meson $K^{\ast }(892)$ with its radiative decay $K^{\ast +}(892)\to K^{+}+\gamma$.

Comments: LaTeX 9 pages; sprocl.sty attached; Invited talk at ``Nuclear and Particle Physics with High-Intensity Proton Accelerators'', (Dec. 3-6, 1996, Tokyo)