Astroparticle Physics

9.2 Thermodynamics of the Early Universe 197particle mass spin colour g (particle andstates states antiparticle)photon (γ ) 0 2 1 2W + , W − 80.4 GeV 3 1 6Z 91.2 GeV 3 1 3gluon (g) 0 2 8 16Higgs > 114 GeV 1 1 1bosons 28u, ū 3MeV 2 3 12d, ¯d 6MeV 2 3 12s, ¯s 100 MeV 2 3 12c, ¯c 1.2 GeV 2 3 12b, ¯b 4.2 GeV 2 3 12t, ¯t 175 GeV 2 3 12e + ,e − 0.511 MeV 2 1 4µ + ,µ − 105.7 MeV 2 1 4τ + ,τ − 1.777 GeV 2 1 4ν e , ¯ν e < 3eV 1 1 2ν µ , ¯ν µ < 0.19 MeV 1 1 2ν τ , ¯ν τ < 18.2 MeV 1 1 2fermions 90Table 9.1Particles of the Standard Modeland their properties [2]Table 9.1 shows the masses and g values of the particles ofthe Standard Model (‘color states’ 1 means a colour-neutralparticle).Here the neutrinos will be treated as only being lefthandedand antineutrinos as only right-handed, i.e., theyonly have one spin state each, which again is related totheir being considered massless. In fact, recent evidence (seeSect. 6.2 on neutrino astronomy) indicates that neutrinos dohave non-zero mass, but the coupling to the additional spinstates is so small that their effect on g ∗ can be ignored.In addition to the particles listed, there are possible Xand Y bosons of a Grand Unified Theory and perhaps supersymmetricpartners for all particle types. It will be the taskof hadron colliders to find out whether such particles can beproduced with present-day accelerator technology. Possiblysuch new particles – if they existed in the early universe –have left imprints on astrophysical data, so that investigationson cosmoarcheology might find evidence for them. Ifone restricts oneself here to the Standard Model and considersa temperature much greater than any of the masses, e.g.,T>1 TeV, one hasneutrino masssupersymmetric particlescosmoarcheology