nLab proton

Contents

Context

Physics

physics, mathematical physics, philosophy of physics

Surveys, textbooks and lecture notes


theory (physics), model (physics)

experiment, measurement, computable physics

Fields and quanta

fields and particles in particle physics

and in the standard model of particle physics:

force field gauge bosons

scalar bosons

matter field fermions (spinors, Dirac fields)

flavors of fundamental fermions in the
standard model of particle physics:
generation of fermions1st generation2nd generation3d generation
quarks (qq)
up-typeup quark (uu)charm quark (cc)top quark (tt)
down-typedown quark (dd)strange quark (ss)bottom quark (bb)
leptons
chargedelectronmuontauon
neutralelectron neutrinomuon neutrinotau neutrino
bound states:
mesonslight mesons:
pion (udu d)
ρ-meson (udu d)
ω-meson (udu d)
f1-meson
a1-meson
strange-mesons:
ϕ-meson (ss¯s \bar s),
kaon, K*-meson (usu s, dsd s)
eta-meson (uu+dd+ssu u + d d + s s)

charmed heavy mesons:
D-meson (uc u c, dcd c, scs c)
J/ψ-meson (cc¯c \bar c)
bottom heavy mesons:
B-meson (qbq b)
ϒ-meson (bb¯b \bar b)
baryonsnucleons:
proton (uud)(u u d)
neutron (udd)(u d d)

(also: antiparticles)

effective particles

hadrons (bound states of the above quarks)

solitons

in grand unified theory

minimally extended supersymmetric standard model

superpartners

bosinos:

sfermions:

dark matter candidates

Exotica

auxiliary fields

Contents

Idea

A proton is a bound state of two up quarks and a down quark, hence a baryon.

flavors of fundamental fermions in the
standard model of particle physics:
generation of fermions1st generation2nd generation3d generation
quarks (qq)
up-typeup quark (uu)charm quark (cc)top quark (tt)
down-typedown quark (dd)strange quark (ss)bottom quark (bb)
leptons
chargedelectronmuontauon
neutralelectron neutrinomuon neutrinotau neutrino
bound states:
mesonslight mesons:
pion (udu d)
ρ-meson (udu d)
ω-meson (udu d)
f1-meson
a1-meson
strange-mesons:
ϕ-meson (ss¯s \bar s),
kaon, K*-meson (usu s, dsd s)
eta-meson (uu+dd+ssu u + d d + s s)

charmed heavy mesons:
D-meson (uc u c, dcd c, scs c)
J/ψ-meson (cc¯c \bar c)
bottom heavy mesons:
B-meson (qbq b)
ϒ-meson (bb¯b \bar b)
baryonsnucleons:
proton (uud)(u u d)
neutron (udd)(u d d)

The bound states of protons and neutrons (jointly: nucleons) in turn are nuclei, the cores of atoms. The proton alone is the nucleus of the hydrogen atom.

In the standard model of particle physics the proton is stable, and experiment highly constrains possible rare proton decay (see there). But some models beyond the standard model (notably many, but not all, GUT models) do imply rare proton decay.

Properties

Mass

A proton has rest mass about a GeV:

m proton0.938GeV. m_{proton} \simeq 0.938 GeV \,.

Spin

The contribution of the constituents (quarks, gluons) to the total spin of the proton turns out to be subtle (“proton spin crisis”) Thomas 08.

References

See also

On the spin of the proton (cf. proton spin crisis):

  • Anthony Thomas, The spin of the proton, Progress in Particle and Nuclear Physics Volume 61, Issue 1, July 2008, Pages 219–228 Quarks in Hadrons and Nuclei — 29th Course International Workshop on Nuclear Physics (arXiv:0805.4437)

  • Anthony Thomas, The resolution of the proton spin crisis, 2008 (pdf)

On the mass of the proton and the mass gap problem (\simconfinement-problem) of QCD:

On the pressure of the proton, via lattice QCD:

On proton stability:

Last revised on November 1, 2023 at 08:20:10. See the history of this page for a list of all contributions to it.