PARTICLE PHYSICS
HADRONS
Quarks can interact via the strong nuclear force. Thus baryons and mesons can interact via the
strong nuclear force. Any particle which experiences the strong force is called a hadron. So,
baryons and mesons are both hadrons. Leptons do not experience the strong force and so are
in a separate class of particle from the hadrons.
The matter particles interact by the four forces of nature, which are gravity, the electromagnetic
force, the strong nuclear force and the weak nuclear force.
BARYONS
If three quarks are combined together, the resulting particle is a baryon. Protons and neutrons
are baryons. A proton consists of two up quarks and a down quark, whilst a neutron is two
down quarks combined with an up quark.
MESONS
If a quark and an anti-quark are combined together, the resulting particle is known as a
meson. The pion and the kaon are the most common examples of mesons. A p+ meson
( u d ) consists of an up quark ( u ) combined with an anti-down ( d ) quark. If a meson is
a combination of a quark and its anti-quark then the meson's charge must be zero. This
is the case for the J/ t/J particle,
A bubble chamber is a vessel filled with
a superheated transparent liquid (most often liquid hydrogen) used to
detect electrically charged particles moving through it.
A cloud chamber consists of a sealed environment containing
a supersaturated vapour of water or alcohol. An energetic charged particle
(for example, an alpha or beta particle) interacts with the gaseous mixture by
knocking electrons off gas molecules via electrostatic forces during collisions,
resulting in a trail of ionized gas particles. The resulting ions act
as condensation centers around which a mist-like trail of small droplets form
if the gas mixture is at the point of condensation. These droplets are visible
as a "cloud" track that persists for several seconds while the droplets fall
through the vapor. These tracks have characteristic shapes. For example, an
alpha particle track is thick and straight, while a beta particle track is wispy
and shows more evidence of deflections by collisions.