nLab positronium

Contents

matter field fermions (spinors, Dirac fields)

flavors of fundamental fermions in the standard model of particle physics:
generation of fermions	1st generation	2nd generation	3d generation
quarks ( $q$ )
up-type	up quark ( $u$ )	charm quark ( $c$ )	top quark ( $t$ )
down-type	down quark ( $d$ )	strange quark ( $s$ )	bottom quark ( $b$ )
leptons
charged	electron	muon	tauon
neutral	electron neutrino	muon neutrino	tau neutrino

bound states:
mesons	light mesons: pion ( $u d$ ) ρ-meson ( $u d$ ) ω-meson ( $u d$ ) f1-meson a1-meson	strange-mesons: ϕ-meson ( $s \bar s$ ), kaon, K-meson ( $u s$ , $d s$ ) eta-meson ( $u u + d d + s s$ ) charmed heavy mesons*: D-meson ( $u c$ , $d c$ , $s c$ ) J/ψ-meson ( $c \bar c$ )	bottom heavy mesons: B-meson ( $q b$ ) ϒ-meson ( $b \bar b$ )
baryons	nucleons: proton $(u u d)$ neutron $(u d d)$

hadrons (bound states of the above quarks)

bosinos:

dark matter candidates

Exotica

auxiliary fields

Idea

In quantum electrodynamics, positronium is a bound state of an electron with a positron (in contrast to that of an electron with a proton, which is a hydrogen atom).

Paul Hoyer, Chapter II of: Bound states – from QED to QCD, Lectures at “Mini-school on theoretical methods in particle physics” at the Higgs Centre for Theoretical Physics, University of Edinburgh on 30 September to 4 October 2013 (arXiv:1402.5005)
Paul Hoyer, Chapter V of: Journey to the Bound States (arXiv:2101.06721)
Xingbo Zhao, Kaiyu Fu, Hengfei Zhao, James P. Vary, Positronium: an illustration of nonperturbative renormalization in a basis light-front approach (arXiv:2103.06719)