Uncertainties in determining parton distributions at large<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>x</mml:mi></mml:math>

Abstract

We critically examine uncertainties in parton distribution functions (PDFs) at large $x$ arising from nuclear effects in deuterium ${F}_{2}$ structure function data. Within a global PDF analysis, we assess the impact on the PDFs from uncertainties in the deuteron wave function at short distances and nucleon off-shell effects, from the use of relativistic kinematics, and from the use of a less restrictive parametrization of the $d/u$ ratio. We find, in particular, that the $d$-quark and gluon PDFs vary significantly with the choice of nuclear model. We highlight the impact of these uncertainties on the determination of the neutron structure functions, and on $W$ boson production and parton luminosity at the Tevatron and the LHC. Finally, we discuss prospects for new measurements sensitive to the $d$-quark and gluon distributions but insensitive to nuclear corrections.