Parton splitting scales of reclustered large-radius jets in high-energy nuclear collisions
Shan-Liang Zhang, M. Yang, Ben-Wei Zhang
Abstract
Abstract We carry out the first theoretical investigation on yields and the hardest parton splitting of large-radius jets reclustered from small radius ( $$R=0.2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:math> ) anti- $$k_t$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>k</mml:mi> <mml:mi>t</mml:mi> </mml:msub> </mml:math> jets in Pb + Pb collisions, and confront them with the recent ATLAS measurements. The Linear Boltzmann Transport (LBT) model is employed for jet propagation and jet-induced medium excitation in the hot-dense medium. We demonstrate that, with their complex structures, the medium suppression of the reclustered large radius jets at $$R=1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> is larger than that of inclusive $$R=0.4$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> </mml:math> jets defined conventionally. The large radius jet constituents are reclustered with the $$k_t$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>k</mml:mi> <mml:mi>t</mml:mi> </mml:msub> </mml:math> algorithm to obtain the splitting scale $$\sqrt{d_{12}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:msub> <mml:mi>d</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:msqrt> </mml:math> , which characterizes the transverse momentum scale for the hardest splitting in the jet. The large-radius jet production as a function of the splitting scale $$\sqrt{d_{12}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:msub> <mml:mi>d</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:msqrt> </mml:math> of the hardest parton splitting is overall suppressed in Pb + Pb relative to p + p collisions due to the reduction of jets yields. A detailed analyses show that the alterations of jet substructures in Pb + Pb also make significant contribution to the splitting scale $$\sqrt{d_{12}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:msub> <mml:mi>d</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:msqrt> </mml:math> dependence of the nuclear modification factor $$R_{AA}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mi>AA</mml:mi> </mml:mrow> </mml:msub> </mml:math> . Numerical results for the medium modifications of the jet splitting angle $$\Delta R_{12}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>Δ</mml:mi> <mml:msub> <mml:mi>R</mml:mi> <mml:mn>12</mml:mn> </mml:msub> </mml:mrow> </mml:math> and the splitting fraction z are also presented.