Multimessenger heavy-ion collision physics

This work studies the production of direct photons in relativistic nuclear collisions, along with hadrons. Radiation from very first instants to final moments evolution is included. The hybrid model used here describes all stages heavy-ion collisions. Chronologically, those are an initial state reflecting collision nuclei described within color glass condensate effective theory; a pre-equilibrium phase based on nonequilibrium linear response; viscous hydrodynamics, and hadronic afterburner. effect both photonic observables highlighted for time. potential photon observables---spectrum, differential elliptic, triangular flow---to reveal chemical equilibration time studied. Finally, we consider ``small systems,'' including $\text{proton}+\text{nucleus}$ collisions light nuclei, as probed by electromagnetic observables. We demonstrate how can signal formation quark-gluon plasma such small systems.