Nuclear modification of heavy flavor decayed dielectrons in relativistic heavy-ion collisions

Abstract

Dielectrons from heavy flavor hadron decays not only constitute a crucial background to their thermal spectrum in high-energy nuclear collisions, from which the temperature of the quark-gluon plasma (QGP) is extracted, but also provide a valuable probe of heavy quark interactions with the QGP. Using a linear Boltzmann transport (LBT) model to describe heavy quark evolution inside the QGP and a hybrid fragmentation-coalescence model for their hadronization, we find heavy quark energy loss softens the invariant mass spectrum of their decayed dielectrons and yields a higher value of the extracted QGP temperature, while coalescence hardens the spectrum and yields a lower value. Taking into account full medium effects leads to higher values of the extracted temperature than using vacuum baselines of heavy flavor decayed dielectrons in analyzing the experimental data. In addition, we find the angular correlations between dielectron pairs are sensitive to heavy quark interactions with the QGP: the radial flow of the QGP enhances the near-side correlations, and scatterings between heavy quarks and the QGP broaden the away-side correlations, with elastic and string interactions playing a dominant role.

Figures (7)

• Figure 1: (Color online) The invariant mass spectra of dielectrons in 0-80% Au+Au collisions at $\sqrt{s_\mathrm{NN}} = 54.4$ GeV. Panel (a) compares between different model calculations of the contributions from charm quark decay, the STAR data on the total yield and the cocktail sum used by STAR in analyzing the data STAR:2024bpc. Panel (b) compares between different fittings (lines) of the QGP temperature to the invariant mass spectra of thermal dielectrons (cross symbols), obtained by subtracting the STAR data on the total yield by different cocktail sums that involve different estimations of the charm decayed dielectrons.
• Figure 2: (Color online) The invariant mass spectra of dielectrons in 0-10% Isobar collisions at $\sqrt{s_\mathrm{NN}} = 200$ GeV. Panel (a) compares between different model calculations of the contributions from charm and bottom quark decays. Panel (b) compares between different fittings (lines) of the QGP temperature to the invariant mass spectra of thermal dielectrons (cross symbols), obtained by subtracting the preliminary STAR data on the total yield (reported at Quark Matter 2025 conference) by different cocktail sums that involve different estimations of the heavy quark decayed dielectrons.
• Figure 3: (Color online) Angular correlations between (a) $e^{+}e^{-}$ pairs and (b) $D\overline{D}$ pairs in $p+p$ collisions at $\sqrt{s} = 5.02$ TeV, compared between different $p_\mathrm{T}$ cuts on the final state particles.
• Figure 4: (Color online) Angular correlations between $e^{+}e^{-}$ pairs in $p+p$ collisions at $\sqrt{s} = 5.02$ TeV, compared between (a) different hard scattering scales with the final $p_\mathrm{T}$ cut fixed, and (b) different final $p_\mathrm{T}$ cuts with the hard scattering scale fixed.
• Figure 5: (Color online) Angular correlations between $e^{+}e^{-}$ pairs in central (0-10%) Pb+Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, compared between with and without the QGP flow effect, Yukawa$+$string and Yukawa interactions, and the $p+p$ baselines. Different panels are for different $p_\mathrm{T}$ cuts on the final state electrons.