The light vector mesons ($ρ$, $ω$, and $ϕ$) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the $ρ$ meson at normal nuclear densities and zero temperature. The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to $e^{+}e^{-}$. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The $ρ$ meson mass spectrum was extracted after the $ω$ and $ϕ$ signals were removed in a nearly model-independent way. Comparisons were made between the $ρ$ mass spectra from the heavy targets ($A > 2$) with the mass spectrum extracted from the deuterium target. With respect to the $ρ$-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion.
Formation of $Σπ$ pairs in nuclear captures of K$^-$ mesons
K $^-$介子在束缚核子上的俘获为研究$\bar{\mathrm{K}}$ N系统运动学阈值以下的$Σπ$对提供了机会。目前，AMADEUS正在研究各种超子-π介子荷电组合。这些数据允许测试同位旋0和1的振幅，从而有可能检测共振$Λ$（1405）态的结构。对照类似的电产生数据，可以检测核介质中$Λ$（1405）的变化。计算了预期光谱及其不确定度。
We present $Φ$- and $J/Ψ$--nuclear bound state energies and absorption widths for some selected nuclei, using potentials in the local density approximation computed from an effective Lagrangian approach combined with the quark-meson coupling model. Our results suggest that these mesons should form bound states with all the nuclei considered provided that these mesons are produced in nearly recoilless kinematics.
Recent results for the $η_c$- and $J/ψ$-nucleus bound state energies for various nuclei are presented. The attractive potentials for the $η_c$ and $J/ψ$ mesons in the nuclear medium originate, respectively, from the in-medium enhanced $DD^{*}$ and $D\bar{D}$ loops in the $η_c$ and $J/ψ$ self energies. Our results suggest that the $η_c$ and $J/ψ$ mesons should form bound states with all the nuclei considered.
