Thermal radiation and direct photon production in Pb–Pb and pp collisions with dielectrons

Electromagnetic probes such as photons and dielectrons (e^{+e^-} pairs) are a unique tool to study the space-time evolution of the hot and dense matter created in ultrarelativistic heavy-ion collisions. At low dielectron invariant mass (m ₄₄), thermal radiation from the hot hadronic phase contributes to the dielectron spectrum via decays of mesons, whose spectral function is sensitive to chiral-symmetry restoration. At larger m ₄₄, thermal radiation from the quark–gluon plasma carries information about the early temperature of the medium. At LHC energies, it is nevertheless dominated by a large background from correlated heavy-flavor hadron decays affected by energy loss and flow in the medium. Complementary to the real photon measurements, dielectron data also allow the extraction of the real direct photon fraction, including thermal photons at low pair transverse momentum p ₓ, ₄₄. The latest ALICE results on dielectron studies in Pb-Pb, and in inelastic and high-multiplicity pp collisions, at s ₍₍ = 5. 02 TeV and at s = 13 TeV, respectively, are presented and compared to simulations and expectations from theory. The status of the Run 3 analysis is also reported.