In General > s.a. atomic physics [exotic atoms]; Bag Model; constants; lattice theories [masses in lattice QCD]; particle physics; Skyrme Model.
* Idea: Mesons and baryons (and pentaquarks), which are strongly-interacting many-body systems consisting of quarks and gluons, with a size of about 1 fm.
@ General references: Chew et al SA(64)feb; Alkofer & von Smekal PRP(01) [IR Green functions]; Gogohia PLB(05)ht/04, ht/06 [mass gap]; Belotsky et al hp/04 [4th generation, bounds]; Afonin IJMPA(07) [parity doubling]; Close CP(08) ["Rumsfeld hadrons"].
@ Hadron structure: Rajeev ht/99 [structure functions]; Jaffe AIP(01)hp [spin distribution]; Drechsel & Walcher RMP(08) [at low Q2]; Hägler PRP(10) [from lattice QCD]; Alexandrou et al RMP(12) [the shape of hadrons]; Hobbs a1408-PhD [non-perturbative].

Types of Hadrons > s.a. neutron; proton.
* Types and classification: The known mesons (singlets and octets) and baryons (singlets, octets and decuplets) belong to representations which are explained as made up from the fundamental representation of flavor SU(6):

q-\(\bar q\) = 3 ⊗ 3bar = 1 ⊕ 8 ;   qqq = 3 ⊗ 3 ⊗ 3 = 1 ⊕ 8 ⊕ 8 ⊕ 10 .

* Pions, π: The isovector fundamental representation of isospin SU(2); The "mesons" postulated by H Yukawa in 1935, discovered by C Powell in emulsions exposed to cosmic rays in 1947.
* Kaons, K: Mesons containing strange quarks; > s.a. CP violation; CPT symmetry.
* Baryons: Hadrons composed of three (valence) quarks; They include p, n, and the heavier, unstable ones, or hyperons; In the large-Nc limit of QCD, baryons can be modeled as solitons, for instance, as Skyrmions.
* Tetraquarks: Evidence has been reported several times since 2003; 2013, Is the Zc(3900) a tetraquark, a hadron molecule, or something different? 2014, The strongest evidence yet is the Z(4430) at the LHC.
* Pentaquarks: 2002–2003, Discovered in Japan and confirmed by others, thought to be made up of five quarks; 2004–2005, More claimed detections [@ news pw(04)mar, charmed], but not seen in further, higher-energy experiments, and considered by some to be a mistake; 2015, Two resonant states of the p and the J/Ψ seen by LHCb; 2019, A pentaquark is a bound state of a baryon and a meson.
@ Mesons: Particle Data Group PLB(04); Choi et al PRL(05) + pw(05)may [hybrid]; Swanson PRP(06) [new heavy]; Cirigliano et al RMP(12) [kaon decays in the standard model, comprehensive overview]; Blum et al PRL(12) + news bnl(12)mar [kaon to decay into two π mesons, lattice QCD]; Aaij et al PRL(13) + news PhysOrg(13)mar [D-meson oscillations]; Bernstein & Holstein RMP(13) [history of the π0, and the QCD chiral anomaly]; news sn(14)oct [discovery of the Ds3*(2860)]; > s.a. dynamical wave-function collapse [flavor oscillations].
@ Baryons: Particle Data Group PLB(04); Cherman & Cohen JHEP(06)ht [and large-Nc limit]; news pn(06)oct, png(06) [periodic table]; news SFN(06)nov [Σb discovered by CDF, heaviest baryons known]; Klempt & Richard RMP(10) [survey of baryon spectroscopy]; Aaij et LHCb PRL(15) [obervation of Ξb]; Gal et al a2003 [from mesons].
@ Tetraquarks: Choi et Belle PRL(03)he + news pw(03)nov [X(3872) mystery meson?]; Gupta IJMPA(05); news pw(07)nov; news pw(10)apr [evidence grows]; Swanson Phy(13), news wired(13)jun [Zc(3900)]; news ns(14)apr, Aaij et LHCb PRL(14) [Z(4430) confirmed]; Olsen PT(14)sep [particles with four or more quarks]; D0 Collaboration PRL(16)-a1602 + news pw(16)feb [X(5568) as a ubds bound state], news pw(16)mar [CERN fails to confirm]; Ablikim et al PRL(17) [spin and parity of the Zc(3900)]; news pw(17)dec [stable tetraquark prediction]; news sn(20)jul [with 4 charm quarks]; Sonnenschein & Weissman a2008; Ablikim et BESIII PRL(21) [observation in e+e collisions].
@ Pentaquarks: Diakonov et al ZPA(97) [prediction]; Nakano et al PRL(03) + pw(03)jul [evidence]; Zhu PRL(03) [in QCD], IJMPA(04) [rev]; Carlson et al PLB(04); Jaffe & Wilczek EPJC(04)hp-conf, news pw(04)mar; Close pw(05)feb; news Nat(05)apr [doubts]; Karliner IJMPA(05); Stancu IJMPA(05); Hicks IJMPA(05); Seth IJMPA(05) [status]; Wei et al JHEP(05) [spin-3/2]; Close CP(06) [rev]; Liu et al IJMPA(14) [search status]; news pw(15)jul, pt(15)jul [best evidence yet]; Aaij et al PRL(15) + Hicks Phys(15) [charmonium-pentaquark states observed at LHCb]; news Phy(16) [confirmation by LHCb]; Aaij et LHCb Collaboration PRL(19) + news sn(19)jun [structure].

Parton Models > s.a. QCD phenomenology.
* Parton models: Treat hadrons as composite particles; Feynman came up with the idea, but in the currently accepted QCD picture, the partons are Gell-Mann's quarks.
@ General references: Kogut & Susskind PRP(73); Drell & Yan AP(00) [high-energy physics applications]; Kim & Noz qp/02-proc [relating quarks and Feynman's partons]; Kancheli hp/02 [and trans-planckian collisions]; Diehl PRP(03), Belitsky & Radyushkin PRP(05) [generalized parton distributions]; Blümlein MPLA(10)-a1007-in [nucleon parton distributions].
@ Phenomenology: Bashindzhagyan & Korotkova a1601 [search for fractional charges in cosmic rays].

Quarks > s.a. astronomical objects [quark stars]; HEP experiments [search for fractional charges]; QCD [including gluons]; QCD phenomenology.
* Idea: Basic building blocks of hadronic matter, which interact by exchange of gluons (and gammas, gravitons, ...).
* History: The first indications of hadron properties that led to the idea of quarks was the isospin symmetry, under an SU(2) that was to become a subgroup of SU(n); The proposal of the first three quarks was made by Gell-Mann in 1964, as mathematical objects belonging to the fundamental (triplet) representation of (flavor) SU(3), an (approximate) symmetry of strong interactions; 1979: Discovery of gluons at DESY; 1996, It is believed that there are 6 flavors, that fill the fundamental representation of flavor SU(6) (not a symmetry) and physically make up hadrons.
* Top: Discovered in 1995; m = 177 GeV (CDF) or 172 GeV (D0) in 1997; 2004, 178.0 ± 4.3 GeV, from D0 results.
* Mass: It is subtle to define, since quark confinement does not allow the measurement in isolation; The short-distance (current algebra) mass is the one appearing in the fundamental Lagrangian, and the long-distance (constituent) mass is the relevant one for hadron-mass calculations; 2010, Supercomputer simulations give \(m_u = 2.01 \pm 0.14\) MeV and \(m_d = 4.79 \pm 0.16\) MeV; 2014, Combined LHC results give \(m_t = 173.34 \pm 0.76\) MeV.
@ General references: Gell-Mann PL(64); Zweig pr(64); Mermin PT(93)dec [pronunciation]; Arkhipov conf(94)-a1410 [quark-quark forces]; Albrow CP(95) [top]; Campagnari & Franklin RMP(97), Liss & Tipton SA(97)sep [top]; Particle Data Group PLB(04); Schiff IJTP(11)-a1012 [classical quark-like particle model]; Fritzsch & Gell-Mann ed-15.
@ Masses: Maity et al IJTP(83) [model]; Chandra Raju & Chintalapati IJTP(05) [in terms of standard model parameters]; Jaffe et al PRD(09)-a0809; news sci(10)apr [more precise values for masses of u and d quarks]; Domínguez IJMPA(10), MPLA(11) [determination in QCD]; Castillo-Felisola et al PRD(13)-a1310 [from the condensation of a fourth family, through torsion]; news hp(14)mar [combined LHC top mass]; > s.a. mass.

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