A global reanalysis of nuclear parton distribution functions

We determine the nuclear modifications of parton distribution functions ofbound protons at scales $Q^2\ge 1.69$ GeV$^2$ and momentum fractions$10^{-5}\le x\le 1$ in a global analysis which utilizes nuclear hard processdata, sum rules and leading-order DGLAP scale evolution. The main improvementsover our earlier work {\em EKS98} are the automated $\chi^2$ minimization,simplified and better controllable fit functions, and most importantly, thepossibility for error estimates. The resulting 16-parameter fit to the N=514datapoints is good, $\chi^2/{\rm d.o.f}=0.82$. Within the error estimatesobtained, the old {\em EKS98} parametrization is found to be fully consistentwith the present analysis, with no essential difference in terms of $\chi^2$either. We also determine separate uncertainty bands for the nuclear gluon andsea quark modifications in the large-$x$ region where they are not stringentlyconstrained by the available data. Comparison with other global analyses isshown and uncertainties demonstrated. Finally, we show that RHIC-BRAHMS datafor inclusive hadron production in d+Au collisions lend support for a strongergluon shadowing at $x<0.01$ and also that fairly large changes in the gluonmodifications do not rapidly deteriorate the goodness of the overall fits, aslong as the initial gluon modifications in the region $x\sim 0.02-0.04$ remainsmall.Comment: 33 pages, 14 figure