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 ii and in the free proton, R-i(A)(x, Q(2)) = f(i/A)(x, Q(2))/f(i)( x, Q(2)), is studied within the framework of the lowest order leading-twist DGLAP evolution. By evolving the initial nuclear distributions obtained wi th the GRV-LO and CTEQ4L sets at a scale Q(0)(2), we show that the ratios R -i(A)(x, Q(2)) are only moderately sensitive to the choice of a specific mo dern set of free parton distributions. We propose that to a good first appr oximation, this parton distribution set-dependence of the nuclear ratios R- i(A)(x, Q(2)) can be neglected in practical applications. With this result, we offer a numerical parametrization of R-i(A)(x, Q(2)) for all parton fla vours i in ally A > 2, and at any 10(-6) less than or equal to x less than or equal to 1 and any 2.25 GeV2 less than or equal to Q(2) less than or equ al to 10(4) GeV2 for computing cross sections of hard processes in nuclear collisions.