Flavor dependence of energy-energy correlators

Energy-energy correlators (EECs) within high energy jets serve as a key experimentally accessible quantity to probe the scale and structure of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions. The CMS Collaboration’s first measurement of the modification to the EEC within single inclusive jets in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>Pb</a:mi><a:mo>+</a:mo><a:mi>Pb</a:mi></a:mrow></a:math> collisions relative to <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi mathvariant="normal">p</c:mi><c:mo>+</c:mo><c:mi mathvariant="normal">p</c:mi></c:mrow></c:math> collisions reveals a significant enhancement at small angles, which may arise from jet transverse momentum <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msub><g:mi>p</g:mi><g:mi>T</g:mi></g:msub></g:math> selection biases due to jet energy loss. We investigate the dependence of jet EECs on the flavor of the initiating parton. The EEC distribution of a gluon jet is broader and the peak of transition from the perturbative to the nonperturbative regime occurs at a larger angle than that of a quark jet. Such flavor dependence leads to the different EECs for <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>γ</i:mi></i:math>-jets and single inclusive jets due to their different flavor composition. It is also responsible for a colliding energy dependence of EECs of single inclusive jets at fixed jet energy. We also investigate the impact of flavor composition variation on the <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>p</k:mi><k:mi>T</k:mi></k:msub></k:math> dependence of the jet EEC. We further propose that a change in the gluon jet fraction in <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:mi mathvariant="normal">A</m:mi><m:mo>+</m:mo><m:mi mathvariant="normal">A</m:mi></m:mrow></m:math> collisions compared to <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mrow><q:mi mathvariant="normal">p</q:mi><q:mo>+</q:mo><q:mi mathvariant="normal">p</q:mi></q:mrow></q:math> can also contribute to a non-negligible enhancement of the medium modified EEC at small angles. Using the model, we predict the reduction of the gluon jet fraction in <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:mrow><u:mi mathvariant="normal">A</u:mi><u:mo>+</u:mo><u:mi mathvariant="normal">A</u:mi></u:mrow></u:math> collisions and estimate its impact on the EEC.