Signatures of charmonium modification in spatial correlation functions

We study spatial correlation functions of charmonium in 2 + 1 flavor QCD using an improved staggered formulation. Contrary to the temporal correlation functions the spatial correlation functions exhibit a strong temperature dependence above the QCD transition temperature. Above this temperature they are sensitive to temporal boundary conditions. Both features become significant at a temperature close to 1.5T(c) and suggest corresponding modifications of charmonium spectral functions.