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Data on the photoproduction of $\omega$ mesons on nuclei have beenre-analyzed in a search for in-medium modifications. The data were taken withthe Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility inBonn. First results from the analysis of the data set were published by D.Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming alowering of the $\omega$ mass in the nuclear medium by 14$%$ at normal nuclearmatter density. The extracted $\omega$ line shape was found to be sensitive tothe background subtraction. For this reason a re-analysis of the same data sethas been initiated and a new method has been developed to reduce the backgroundand to determine the shape and absolute magnitude of the background directlyfrom the data. Details of the re-analysis and of the background determinationare described. The $\omega$ signal on the $Nb$ target, extracted in there-analysis, does not show a deviation from the corresponding line shape on a$LH_2$ target, measured as reference. The earlier claim of an in-medium massshift is thus not confirmed. The sensitivity of the $\omega$ line shape todifferent in-medium modification scenarios is discussed.

In-medium $\omega$ mass from the $\gamma + Nb \to \pi^{0}\gamma + X$ reaction