nCTEQ project is an extension of the CTEQ
collaborative effort to determine parton distribution functions inside of a free proton. It generalizes the
free-proton PDF framework to determine densities of partons in bound protons (hence nCTEQ which stands for nuclear CTEQ).
More details on the framework
and the first results can be found in arXiv:09072357 [hep-ph].
The effects of the nuclear environement on the parton densities can be shown as modified parton densities
where all black curves stand for free proton PDF and red, green, blue, cyan, pink, yellow, magenta and brown curves show PDF in protons bound in nuclei - from deuterium (red) to lead (brown).
An alternative way how effects of nuclear environement can be displayed is in ratios of Deep Inelastic Scattering (DIS) structure functions e.g. ratios of of the structure function F2 for a neutral current DIS as in the figure below on the left or ratios of of the same structure function F2 but for a charged current DIS.