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subnucleon

Subnucleon is a term sometimes used to refer to the internal components of a nucleon (proton or neutron) at distance scales smaller than the overall size of the nucleon. In contemporary physics, the standard description of this internal structure is provided by quantum chromodynamics, which treats quarks and gluons as the fundamental degrees of freedom inside hadrons. The label subnucleon is not widely standardized, and most discussions favor language about nucleon structure, partons, or the quark–gluon content of nucleons.

The interior of a nucleon consists of valence quarks—two up and one down in the proton, two

Experiments such as deep inelastic scattering and high-energy hadron collisions, together with lattice QCD calculations, reveal

Beyond the established quark–gluon picture, some speculative ideas propose deeper substructure (for example, preons), but there

down
and
one
up
in
the
neutron—plus
a
sea
of
quark–antiquark
pairs
and
gluons.
These
constituents
collectively
generate
the
nucleon's
mass
and
quantum
numbers
and
interact
via
the
strong
force,
with
color
confinement
preventing
free
quarks
or
gluons
from
escaping.
The
distribution
of
momentum
and
spin
among
partons
depends
on
the
energy
scale
at
which
the
nucleon
is
probed.
and
quantify
subnucleon
structure.
Parton
distribution
functions
describe
the
probability
of
finding
a
parton
carrying
a
given
fraction
of
the
nucleon’s
momentum,
while
form
factors
reflect
the
spatial
distribution
of
charge
and
magnetization
within
the
nucleon.
is
no
experimental
evidence
for
such
subnucleonic
layers.
Current
understanding
remains
that
quarks
and
gluons
are
the
relevant
degrees
of
freedom
at
accessible
energy
scales,
governing
the
properties
and
interactions
of
protons
and
neutrons.