Hadrons |

**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 *Q*^{2}]; 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.

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**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
transplanckian 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 ± 0.14 MeV and *m*_{d} = 4.79 ± 0.16 MeV; 2014, Combined LHC results give *m*_{t} = 173.34 ± 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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