The scale dependent nuclear effects in parton distributions for practical applications

The scale dependence of the ratios of parton distributions in a proton of a nucleus A and in the free proton, RAi(cursive Greek chi, Q2) = fi/A(cursive Greek chi, Q2)/fi(cursive Greek chi, Q2), is studied within the framework of the lowest order leading-twist DGLAP evolution. By evolving the initial nuclear distributions obtained with the GRV-LO and CTEQ4L sets at a scale Q20, we show that the ratios RAi(cursive Greek chi, Q2) are only moderately sensitive to the choice of a specific modern set of free parton distributions. We propose that to a good first approximation, this parton distribution set-dependence of the nuclear ratios RAi(cursive Greek chi, Q2) can be neglected in practical applications. With this result, we offer a numerical parametrization of RAi(cursive Greek chi, Q2) for all parton flavours i in any A > 2, and at any 10-6 ≤ cursive Greek chi ≤ 1 and any 2.25 GeV2 ≤ Q2 ≤ 104 GeV2 for computing cross sections of hard processes in nuclear collisions.