Relating the proton, neutron and deuteron structure functions in the covariant Bethe-Salpeter formalism

The neutron structure function F n 2 (x) is evaluated within the kinematic range 10−3 < x < 1 from the deuteron and proton data by employing relativistic theoretical description of FD 2 (x) and several assumptions on the high-x asymptotics of F n 2 (x)/F p 2 (x). It is shown that new measurements of F D 2 (x) in the range 0.6 < x ≤ 0.8 would substantially improve understanding of the relation between d and u valence quarks in the limit x → 1.