Types of Particles  

In General > s.a. Bosons; fermions; particle models, classical and quantum; particle physics and effects.
* Classification: Labeling is provided by the irreducible representations of the lorentz group; > s.a. BMS Group.
* Remark: Particle multiplets are usually written down as if they were column vectors; They are not; They are actually to be thought of as (orthonormal) bases in some vector space that carries the representation of the group in question; The column vectors are the states.
* Numbers: The number of baryons in the observable universe is of the order of \(10^{80}\), as is the number of electrons; The number of photons is about \(10^{89}\), as is the estimated number of neutrinos; According to D Page, the number of gravitons could be more than twenty orders of magnitude larger yet.
* Supersymmetric partners: All known bosons are assumed to have a partner denoted by the suffix "-ino" and all fermions one denoted by the prefix "s-"; These particles should decay into an extremely weakly interacting Lightest Supersymmetric Particle, of at least 40 GeV; The 2002 lower bound on the gluino mass is 195 GeV.
@ General properties: Millikan & Richman ht/01 [mass formula and geometry]; Glashow a1106 [search for hidden attributes shared by quarks and leptons]; Furey PLB(15)-a1603 [quarks and leptons from division algebras, charge quantization from a number operator]; Page a1605 [number of gravitons in the observable universe]; Saar & Groote AACA(17)-a1606 [massless particles are not limiting cases of massive particles].
@ Electric dipole moments: Fortson et al PT(03)jun [fundamental]; > s.a. electromagnetism; neutron; particle physics [beyond the standard model].
@ Other properties: volume PLB(90)239; Barnett et al (PDG) PRD(96), RMP(96), PLB(04); Tanabashi et al PRD(18); > s.a. Gyromagnetic Ratio; statistics.

Leptons > s.a. electron [including positron]; equivalence principle and quantum equivalence principle; neutrino.
* Idea: Weakly interacting particles, e, μ, τ, and the neutrinos.
* Lepton number: We would know that it can be violated if we had conclusive evidence for neutrinoless double-beta decay, a process beyond the standard model.
* Tau lepton: Its mass is 1776.61 ± 0.13 (stat) ± 0.35 (syst) MeV.
* Lepton universality: The fact that in the standard model of particle physics, the electron, muon, and tau particle interact with other particles, either via the electromagnetic or the weak force, in identical ways; 2014, This claim has been challenged by an LHC experiment on B meson decay.
@ Tau lepton: Stahl 00 [r PT(00)jul]; Eidelman & Passera MPLA(07) [anomalous magnetic moment]; Belous et BELLE PRL(07) [mass].
@ Related topics: Particle Data Group PLB(04) [list]; Belle Collaboration PLB(05) [search for lepton flavor violation];
Roberts & Marciano ed-09 [lepton dipole moments]; Aaij et al PRL(14) [test result on lepton universality]; > s.a. Singletons; symmetry breaking; torsion [interactions].

Muon > s.a. QED phenomenology; supersymmetry.
* Applications: Muon spin rotation (muSR) method to map magnetic fields from the detection of decay positrons; 2005, Muons suggested as probes of containers in search for hidden nuclear materials.
* Anomalous magnetic moment, g−2: A discrepancy with theory may possibly indicate supersymmetric particles.
* History: 1936, Discovery of the muon (I I Rabi: "Who ordered that?"); 2001, Data show a 2.6-σ deviation of the muon's g − 2 from standard model predictions; It later went away; 2017, The Fermilab g − 2 experiment will measure the magnetic moment with much greater precision.
@ Magnetic moment: Everett et al PRL(01)hp [and supersymmetry]; news pw(01)mar [discrepancy with standard model]; Feng et al PLB(03); Blum PRL(03) [hadronic contribution, lattice]; Hertzog pw(04)mar; Passera JPG(05)hp/04 [standard model, rev]; Melnikov & Vainshtein 06; Miller et al RPP(07) [rev]; Jegerlehner & Nyffeler PRP(09); McKeen AP(11) [contributions from hidden sector]; de Rafael NPPS(13)-a1210 [update, standard model]; news nat(17)apr, sci(18)jan [the Fermilab g−2 experiment]; news pw(18)feb + Visser a1802 [on explaining the anomaly using general relativity]; Keshavarzi et al PRL(18) + Roberts Phy(18) [complete reevaluation]; Roberts a1811-proc [hist]; Abi et al PRL(21) + news nyt(21)apr, sn(21)apr, giz(21)apr + Cushman Phy(21) [g−2 results 4.2-σ away from SM predictions]; > s.a. Gravitino; quantum-gravity phenomenology [g − 2].
@ Related topics: Dolgov et al NPB(97) [oscillations?].
> Online Resources: see the g − 2 experiment homepage.

Other Types > s.a. particle statistics [paraparticles]; quantum particles [superparticles].
* Fundamental particles vs quasiparticles: Quasiparticles arise as collective states of fundamental fields, often in condensed-matter systems, and may constitute a longer list of particles than found in the standard model, for example because they are not constrained by Lorentz invariance.
@ New particles: Fairbairn et al PRP(07) [stable massive, search]; De Angelis et al PRD(07) [proposal of light spin-0 boson]; news SciNews(15)jul [observation of massless Weyl fermions]; Criado et al a2105 [higher-spin, at colliders].
@ Special field configurations: Ward ht/05-en; Feranchuk & Feranchuk Sigma(07)-a0712 [electrons and positrons in QED].
@ Fakeons: Anselmi CQG(19)-a1809 [and microcausality violation]; Piva a1905-GRF [and gravity]; Anselmi & Marino CQG-a1909 [gravitational waves and the Hubble constant]; Anselmi a1911-proc [and quantum gravity].
@ Gauge and Higgs bosons: Eidelman et al PLB(04); Particle Data Group PLB(04); > s.a. electroweak theory [W, Z]; higgs boson.
> Known particles: see graviton; hadrons [including baryons, mesons, quarks]; photon; QCD [gluons].
> Field configurations: see field theory; geon; instanton; Kink; Magnon; Meron; monopole; Phonon; Quasiparticle; Roton; Skyrmion; soliton; Sphaleron.
> Predicted particles: see Axino; axion; Gravitino; GUTs [leptoquarks].
> More hypothetical particles: see Hyperphoton; Notoph; Newtorites; Paraphoton; Preons; Pyrgon; tachyon.

Online Resources > see Particle Data Group website.

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