Figures from paper submitted to Physical Review C

Abstract:

This paper presents the first measurement of the angle between different jet axes (denoted as $ΔR$) in Pb$-$Pb collisions. The measurement is carried out in the 0$-$10% most-central events at $\sqrt{s_{\rm NN}} = 5.02$ TeV. Jets are assembled by clustering charged particles at midrapidity using the anti-$k_{\rm T}$algorithm with resolution parameters $R=0.2$ and $0.4$ and transverse momenta in the intervals $40 <~ p_{\rm T}^{\rm ch jet} <~ 140$ GeV/$c$ and $80 <~ p_{\rm T}^{\rm ch jet} <~ 140$ GeV/$c$, respectively. Measurements at these low transverse momenta enhance the sensitivity to quark$-$gluon plasma (QGP) effects. A comparison to models implementing various mechanisms of jet energy loss in the QGP suggests that the observed narrowing of the Pb$-$Pb distribution relative to pp can be explained if quark-initiated jets are more likely to emerge from the medium than gluon-initiated jets. These new measurements disfavor intra-jet $p_{\rm T}$ broadening as implemented in a simple model calculation with the BDMPS formalism for energy loss in the QGP. The comparison of Pb$-$Pb and pp collisions shows sensitivity to the angular scale at which the QGP can resolve two independent splittings, favoring mechanisms that incorporate incoherent energy loss.

Phys.Rev.C 113 (2026) 4, 044905
e-Print: arXiv:2303.13347 | PDF | inSPIRE