We present a new determination of the nonsinglet structure function ${\mathit{F}}_2^{\mathit{p}}$ - ${\mathit{F}}_2^{\mathit{n}}$ at ${\mathit{Q}}^2$=4 ${\mathrm{GeV}}^2$ using recently measured values of ${\mathit{F}}_2^{\mathit{d}}$ and ${\mathit{F}}_2^{\mathit{n}}$/${\mathit{F}}_2^{\mathit{p}}$. A new evaluation of the Gottfried sum is given, which remains below the simple quark-parton model value of 1/3.

• Received 1 March 1994

DOI:https://doi.org/10.1103/PhysRevD.50.R1