stage of the Big Bang, the tiny expanding Universe is filled with radiation
creating pairs of particles and antiparticles, and pairs of particles and antiparticles
annihilating back into radiation.
from observing elementary particles in the present era that every known particle
has an antiparticle with the opposite charge and the same spin. (Particles with
zero charge are their own antiparticles.) The antiparticle of a quark
is called an antiquark. At the beginning of the Big Bang, the
Universe was so hot that quarks and antiquarks were created from radiation and
annihilated back into radiation at a high rate. There was an equal number of
quarks and antiquarks on the average at any one moment.
the Universe expanded, it cooled, and the cooler radiation was less likely to
create quark-antiquark pairs. As quarks and antiquarks "froze" out
of the radiation background, a greater number of quarks than antiquarks was
this must have happened, because we observe more quarks than antiquarks today.
All of the protons and neutrons in all of the elements in the Universe are made
out of quarks, not antiquarks. Quarks are clearly more numerous than antiquarks.
quark excess can't be explained using the Standard Model of particle physics.
Therefore the domination of quarks over antiquarks is an area where studies
of the early Universe could shed light on particle physics we haven't yet been
able to study by direct particle scattering in an accelerator.