In this work, we propose that dilepton emission rate (DER) could possibly carry the characteristic structures associated with the chiral criticality of the QCD system based on the extended Polyakov-quark-meson model. The model could successfully capture two main mechanisms for dilepton production, ${\pi }^{+}{\pi }^{-}$ and quark-antiquark annihilations on one hand, and self-consistently account for chiral transition and (de)confinement on the other hand. All the moments of the DER peak exhibit extremal features similar to those of light-quark mass along the chemical freeze-out lines, thus the DER can reflect the change of chiral symmetry and criticality. However, the DER is relatively too low to produce a sufficient number of thermal dileptons in each heavy-ion collision, which prevents the implementation of event-by-event measurements of the moments. As an alternative, we propose to study the baseline-subtracted DER: For a given low center of mass of dileptons, the reduced baseline-subtracted DER exhibits a nonmonotonic behavior in the region where the light-quark mass changes most rapidly.

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• Photon, lepton & quark production
• QCD phase transitions
• Relativistic heavy-ion collisions