Dilepton emission in heavy ion collisions and chemical equilibrium of QCD matter

We study thermal dilepton production and anisotropic flow in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02\mathrm{T}\mathrm{e}\mathrm{V}$ using next-to-leading-order (NLO) thermal QCD dilepton emission rates. A hybrid model (IP-Glasma+\kompost+MUSIC+UrQMD) simulates the collision evolution. The role of the pre-equilibrium stage in dilepton observables is examined. We also explore how chemical equilibrium in QCD matter affect dilepton observables.