Nuclear medium effects on the meson

The meson in dense matter is analyzed by means of a unitary approach in coupled channels based on the local hidden gauge formalism. The self-energy and the corresponding spectral function in the nuclear medium are obtained. We observe that the develops a width in matter up to five times bigger than in free space. We also estimate the transparency ratio of the γA→K+K⁎−A′ reaction. This ratio is an excellent tool to detect experimentally modifications of the meson in dense matter.