Observation of $rho / omega$ Meson Modification in Nuclear Matter


Abstract in English

We have measured invariant mass spectra of electron-positron pairs in the target rapidity region of 12GeV p+A reactions. We have observed a significant difference in the mass spectra below the $omega$ meson between p+C and p+Cu interactions. The difference is interpreted as a signature of the $rho/omega$ modification at normal nuclear-matter density.

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