Up and down quark structure of the proton

Abstract

We report an improved measurement of the valence <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>u</a:mi></a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>d</c:mi></c:math> quark distributions from the forward-backward asymmetry in the Drell-Yan process using <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>8.6</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mi>fb</e:mi><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:math> of data collected with the D0 detector in <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>p</g:mi><g:mover accent="true"><g:mi>p</g:mi><g:mo stretchy="false">¯</g:mo></g:mover></g:math> collisions at <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msqrt><k:mi>s</k:mi></k:msqrt><k:mo>=</k:mo><k:mn>1.96</k:mn></k:math>. This analysis provides the values of new structure parameters that are directly related to the valence up and down quark distributions in the proton. In other experimental results measuring the quark content of the proton, <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>d</m:mi></m:math> quark contributions are mixed with those from other quark flavors. In this measurement, the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>u</o:mi></o:math> and <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mi>d</q:mi></q:math> quark contributions are separately extracted by applying a factorization of the QCD and electroweak portions of the forward-backward asymmetry. Published by the American Physical Society 2024