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 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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