NNLO QCD calculation of hadron multiplicities in light-quark jets at lepton colliders

We present the calculation of next-to-next-to-leading-order (NNLO) QCD corrections to hadron multiplicities in light-quark jets at lepton colliders, employing the “projection-to-Born” (P2B) method implemented in the FMNLO program. Taking the next-to-leading-order result as an example, we rigorously establish the validity of our P2B-based calculation. We then present NNLO predictions for the normalized asymmetry <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>D</a:mi><a:msup><a:mi>K</a:mi><a:mo>−</a:mo></a:msup></a:msub></a:math> between hadron and antihadron production in light-quark jets and compare them with SLD data. We find that a suppression of these SLD measurements relative to NPC23 predictions for <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>D</c:mi><c:msup><c:mi>K</c:mi><c:mo>−</c:mo></c:msup></c:msub></c:math> emerges in the intermediate <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msub><e:mi>z</e:mi><e:mi>h</e:mi></e:msub></e:math> domain (<g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mn>0.2</g:mn><g:mo>≲</g:mo><g:msub><g:mi>z</g:mi><g:mi>h</g:mi></g:msub><g:mo>≲</g:mo><g:mn>0.7</g:mn></g:math>). We expect that incorporating these SLD data into global QCD fits will enable improved determination of fragmentation functions.