Jet cone size dependence of single inclusive jet suppression due to jet quenching in Pb + Pb collisions at s N N = 5.02 TeV

Jet suppression in high-energy heavy-ion collisions results from jet energy loss and transverse-momentum broadening during jet propagation through the quark-gluon plasma (QGP). The jet cone size ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>R</a:mi> </a:math> ) dependence of this suppression offers crucial insights into the energy loss mechanisms and QGP transport properties. In our study, we implement a comprehensive approach within the perturbative QCD parton model that incorporates both elastic and inelastic energy loss mechanisms. For elastic processes the contribution from recoiling thermal partons reduces the net in-cone energy loss for a given jet radius. For inelastic processes, we account for the angular distribution of radiated gluons, the thermalization of soft gluons, and transverse-momentum broadening. Using this framework, we calculate the jet nuclear modification factors ( <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:msub> <b:mi>R</b:mi> <b:mrow> <b:mi>A</b:mi> <b:mi>A</b:mi> </b:mrow> </b:msub> </b:math> ) and their double ratios <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:msub> <c:mi>R</c:mi> <c:mrow> <c:mi>A</c:mi> <c:mi>A</c:mi> </c:mrow> </c:msub> <c:mrow> <c:mo>(</c:mo> <c:mi>R</c:mi> <c:mo>=</c:mo> <c:mn>0.2</c:mn> <c:mo>–</c:mo> <c:mn>1.0</c:mn> <c:mo>)</c:mo> </c:mrow> <c:mo>/</c:mo> <c:msub> <c:mi>R</c:mi> <c:mrow> <c:mi>A</c:mi> <c:mi>A</c:mi> </c:mrow> </c:msub> <c:mrow> <c:mo>(</c:mo> <c:mi>R</c:mi> <c:mo>=</c:mo> <c:mn>0.2</c:mn> <c:mo>)</c:mo> </c:mrow> </c:mrow> </c:math> , and systematically compare with ALICE, ATLAS, and CMS data in 0–10% and 30–50% <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:mi>Pb</d:mi> <d:mo>+</d:mo> <d:mi>Pb</d:mi> </d:mrow> </d:math> collisions at <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:msqrt> <e:msub> <e:mi>s</e:mi> <e:mrow> <e:mi>N</e:mi> <e:mi>N</e:mi> </e:mrow> </e:msub> </e:msqrt> <e:mo>=</e:mo> <e:mn>5.02</e:mn> <e:mspace width="0.28em"/> <e:mi>TeV</e:mi> </e:mrow> </e:math> . Numerical results show that <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:msub> <g:mi>R</g:mi> <g:mrow> <g:mi>A</g:mi> <g:mi>A</g:mi> </g:mrow> </g:msub> </g:math> increases with the cone size <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mi>R</h:mi> </h:math> because the in-cone energy loss decreases at larger radii. Specifically, as the radius <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mi>R</i:mi> </i:math> grows, the probability for elastically scattered partons to escape the jet cone and the likelihood for radiated gluons to fall outside the cone both decrease, resulting in a net reduction of energy loss. The <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:msub> <j:mi>R</j:mi> <j:mrow> <j:mi>A</j:mi> <j:mi>A</j:mi> </j:mrow> </j:msub> </j:math> double ratios are approximately unity for small radii ( <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:mrow> <k:mi>R</k:mi> <k:mo>=</k:mo> <k:mn>0.4</k:mn> </k:mrow> </k:math> relative to <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"> <l:mrow> <l:mi>R</l:mi> <l:mo>=</l:mo> <l:mn>0.2</l:mn> </l:mrow> </l:math> ) and at high <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:msub> <m:mi>p</m:mi> <m:mi mathvariant="normal">T</m:mi> </m:msub> <m:mo>≳</m:mo> <m:mn>200</m:mn> <m:mspace width="0.28em"/> <m:mi>GeV</m:mi> <m:mo>/</m:mo> <m:mi>c</m:mi> </m:mrow> </m:math> , in agreement with the data within uncertainties.