2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203091We study production and equilibration of pions and muons in relativistic electron-positron-photon plasma at a temperature $T\ll m_μ, m_π$. We argue that the observation of pions and muons can be a diagnostic tool in the study of the initial properties of such a plasma formed by means of strong laser fields. Conversely, properties of muons and pions in thermal environment become accessible to precise experimental study.16 pages, v3 imporved presentation in response to PRD review, v4 minor corrections presumably the "to be" published versionHigh Energy Physics - PhenomenologyNuclear ExperimentNuclear TheoryOpticsPlasma Physicstext