Standard
Model of Particle Physics |

**In General** > s.a. cosmological
standard model; history of particle physics; particle
physics [context].

* __Particles__: Classified
by representations of the symmetry group SU(3) × SU(2) × U(1);
Presently known particles can be divided into quarks (*u*, *d*; *c*, *s*; *t*, *d*)
(each in 3 colors), leptons (*e*, *ν*_{e}; *μ*,
*ν*_{μ}; *τ*, *ν*_{τ}),
and gauge bosons (graviton, 8 gluons, *W*^{ ±},
*Z*); Others are predicted by various extensions, like Higgs scalars (from spontaneous gauge
symmetry breaking), gravitinos (> see supergravity),
etc; Cosmology puts an upper bound of 4 on the number of generations.

* __Interactions__: Four of them explain all presently known phenomena.

Interaction |
Strength |
Range |
Exchange particles |
Theory |
See also |

gravitational | 10^{–40} |
∞ | graviton | > general relativity | > other theories, quantum gravity |

weak | 10^{–15} |
10^{–15} cm |
W^{ ±}, Z |
> electroweak | |

electromagnetic | 10^{–2} |
∞ | photon | > electroweak | > other theories, QED |

strong | 1 | 10^{–13} cm |
gluons | > QCD |

The weak and electromagnetic interactions have in fact been unified by
the Weinberg-Salam electroweak theory, which has been experimentally tested;
aka hypercharge force;
There could be additional forces (> see fifth force).

* __Theoretical problems__:
Why do weak interactions couple differently to left-handed and right-handed
particles? The theoretical basis for the Cabibbo-Kobayashi-Maskawa matrix (too many
parameters); The standard model is not enough to account for
baryogenesis (GUTs or supersymmetry of some type are needed); > s.a. Landau
Pole and Hierarchy Problem.

@ __General references__: Leader & Predazzi 95; Cahn RMP(96)
[18 parameters]; Herrero hp/98-ln;
Riles CP(98)
[tests]; Bertin et al RNC(00)
[CKM matrix]; Quigg AIP(00)hp;
Rosner AJP(03)apr [RL];
Particle Data Group PLB(04)
[reference]; Morii et al 04;
Oerter 05 [I]; Burgess & Moore 06; Cottingham & Greenwood 07;
McCabe ed-PFP(07) [structure and interpretation]; Mann 09; Langacker 09; Perović SHPMP(11) [missing experimental challenges]; Robinson 11 [introduction]; Schwartz 13, Han 14 [and qft];
Becchi & Ridolfi 14 [II]; Donoghue et al 14; Kibble a1412-conf [rev]; Butterworth PTRS(16)-a1601-conf [successes and challenges]; Maiani & Rolandi ed-16; 't Hooft IJMPA(16).

@ __Number of generations__: van der Bij PRD(07) [three generations and the topology of the universe]; Gould a1011 [anthropic argument for three generations]; Kaplan & Sun PRL(12) [spacetime as a topological insulator]; He et al a1408 [algebraic geometry and the phenomenology of generations]; > s.a. beyond the standard model [beyond three generations].

**Theoretical Aspects** > s.a. group
theory; Hypercharge;
renormalization of gauge theories; unified theories.

* __Isospin__:
A quantum number associated with an SU(2) group, related to a transformation
between the *u* and *d* quarks; The isospin SU(2) is a symmetry
group for strong interactions, but is broken when electromagnetic interactions are turned
on, since *Q* = \(1\over2\)*B* + *I*_{3},
so [*Q*, *I*_{1,2}] ≠ 0;
Usually though *H*_{em} \(\ll\) *H*_{strong},
and the breaking is small.

* __Cabibbo angle__: The parameter *θ*_{C} that allows to obtain
the weakly interacting eigenstates as linear combinations of the quark mass
eigenstates, like

*d*' = *d* cos *θ*_{C} +
*s* sin *θ*_{C}, *s*'
= –*d* sin *θ*_{C} + *s* cos
*θ*_{C} .

@ __General references__: Iliopoulos a1101-conf [Cabibbo angle, history].

@ __Hamiltonian / Dirac treatment__: Lusanna NPPS(97)ht, ht/97-conf;
Lusanna & Valtancoli IJMPA(98)ht/97.

@ __Other theoretical aspects__: Grigore a1506-conf [perturbation theory up to second order (in the causal approach)].

> __Related topics__:
see Calabi-Yau Spaces; CKM Matrix; clifford algebra; conformal
symmetry; fine-structure constant [variation]; Fine Tuning; Krajewski
Diagrams; PMNS Matrix.

**Phenomenology and Experiment** > s.a. experimental physics and particle physics / early-universe
cosmology; QCD
phenomenology.

* __And experiment__: 1989,
So far seems to be ok with experiment down to 10^{–16} cm;
Some predictions confirmed to 10^{–12};
No problem including a fourth family, and can accommodate *ν* oscillations;
Possible problems include same sign dileptons; The decay *Z*^{0} → *l*^{+}* l*^{–} *γ*,
and, Where is the Higgs particle? 2002, The experimental value of the CP violation parameter
sin 2*β* approaches prediction, but the *g*–2 problem remains.

@ __Cosmology__: Kusenko & Langacker PLB(97)
[vacuum]; Bjorken PRD(01)
[and Λ], PRD(03)ht/02; > s.a. vacuum phenomenology.

@ __Particle physics__: Froggatt et al NPB(94)
[fermion masses]; Dolgov NPB(97)
[mass corrections in expanding universe]; Gynther & Vepsäläinen
JHEP(06)
[high-*T*, pressure]; Mangano IJMPA(08)-a0802-in
[LHC preview]; news symm(11)jul [Ξ_{b} discovery by CDF]; Blümlein a1205-proc [perturbative precision calculations]; > s.a. astrophysics; atomic
physics; electroweak theory [including *W* and *Z *bosons,
Higgs particle]; higgs field; Regge Trajectory; Sum
Rules.

**Variations / Generalizations** > s.a. physics beyond
the standard model [including non-commutative geometry].

@ __Variations__: Spaans gq/97 [topological];
Lombardo hp/01-ln [at finite temperature, phase transitions]; Srivastava & Brodsky PRD(02)
[light front]; Blaha ht/02 [as
quantum computer]; Davoudiasl et al PLB(05)hp/04 [new
minimal model]; Ziino MPLA(07)
[with neutrino masses and
oscillations]; Zubkov PLB(07)
[extra discrete symmetry]; Grinstein et al PRD(08)-a0704 [Lee-Wick,
with Higgs mass stabilization]; Alberghi et al a0804 [vacuum
energy and additional
particles]; Sannino MPLA(11) [as the magnetic dual of a gauge theory with only fermionic matter]; Masina & Sannino a1110 [dark-sector modifications]; Senjanović MPLA(17)-a1610-proc [left-right symmetric theory].

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jan 2018