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Emergence of thermal recoil jets in high-energy heavy-ion collisions

Peng Jing, Yichao Dang, Yang He, Shanshan Cao, Li Yi, Xin-Nian Wang

Abstract

In the established paradigm of jet quenching in relativistic heavy-ion collisions, jets from initial hard parton scatterings are suppressed due to their interaction with the quark-gluon plasma (QGP) as they traverse the hot medium, serving as crucial tomographic probes of QGP properties. The QGP is also capable of absorbing and reprocessing energy deposited by the hard jets into emergent jet-like objects, providing a novel production mechanism of thermal recoil jets. These emergent thermal recoil jets exhibit distinct transverse momentum ($p_\mathrm{T}$) and jet-size ($R$) dependencies different from the hard jets, and naturally explain the puzzling observation of the enhanced yields of hadron or photon triggered jets at large azimuthal angle and solely at small $p_\mathrm{T}$ and large $R$. These thermal recoil jets are predicted to have unique substructures, such as their jet shape that increases with the radius and the thermal-like distribution of their constituents, which can be verified in future experimental analyses.

Emergence of thermal recoil jets in high-energy heavy-ion collisions

Abstract

In the established paradigm of jet quenching in relativistic heavy-ion collisions, jets from initial hard parton scatterings are suppressed due to their interaction with the quark-gluon plasma (QGP) as they traverse the hot medium, serving as crucial tomographic probes of QGP properties. The QGP is also capable of absorbing and reprocessing energy deposited by the hard jets into emergent jet-like objects, providing a novel production mechanism of thermal recoil jets. These emergent thermal recoil jets exhibit distinct transverse momentum () and jet-size () dependencies different from the hard jets, and naturally explain the puzzling observation of the enhanced yields of hadron or photon triggered jets at large azimuthal angle and solely at small and large . These thermal recoil jets are predicted to have unique substructures, such as their jet shape that increases with the radius and the thermal-like distribution of their constituents, which can be verified in future experimental analyses.

Paper Structure

This paper contains 3 equations, 5 figures.

Figures (5)

  • Figure 1: (Color online) The $I_\mathrm{AA}$ factor of hadron triggered charged jets as a function of the jet $p_\mathrm{T}$ in central (0-10%) Pb+Pb collisions at $\sqrt{s_{\mathrm {NN}}} = 5.02$ TeV from LBT simulations for unquenched jets (baseline, dot-dashed), quenched jets with only inelastic scatterings (dashed) and with both elastic and inelastic scatterings (solid), as compared to the ALICE data ALICE:2023qve, (a) for jets with radius $R=0.2$ and (b) for $R=0.4$.
  • Figure 2: (Color online) The $I_\mathrm{AA}$ of $h$-jets as a function of the azimuthal angle between jets and their trigger hadrons in central (0-10%) Pb+Pb collisions at $\sqrt{s_{\mathrm {NN}}} = 5.02$ TeV, compared between the LBT calculations with and without including elastic scatterings, and the ALICE data ALICE:2023qve. Different panels are for different $p_\mathrm{T}$ and $R$ of the recoil jets.
  • Figure 3: (Color online) The fractional $p_\mathrm{T}$ of recoil partonic jets contributed by the medium response as a function of the jet $p_\mathrm{T}$ in central (0-10%) Pb+Pb collisions at $\sqrt{s_{\mathrm {NN}}}=5.02$ TeV, compared between different jet radii.
  • Figure 4: (Color online) The jet shape of hadron triggered charged jets $R\rho(r)$ as a function of the scaled radius $r/R$ in central (0-10%) Pb+Pb collisions at $\sqrt{s_{\mathrm {NN}}} = 5.02~\mathrm{TeV}$, compared between different jet $p_\mathrm{T}$ and jet-cone size $R$.
  • Figure 5: (Color online) The transverse mass distribution of pions inside the recoil charged jets in central (0-10%) Pb+Pb collisions at $\sqrt{s_{\mathrm {NN}}} = 5.02~\mathrm{TeV}$, compared between different $p_\mathrm{T}$ and $R$ of jets.