What is a quark?
A: A quark is a type of elementary particle and a fundamental constituent of
matter.
Quarks combine to form composite particles called what?
A: Hadrons, the most stable of which are protons and
neutrons.
All commonly observable matter is composed of what?
A: Up quarks, down quarks and electrons.
Owing to a phenomenon known as color confinement,
quarks are never found in what?
A: In isolation; they can be found only within hadrons.
Hadrons include what?
A: Baryons (such as protons and neutrons) and mesons, or in quark–gluon
plasmas.
For this reason, much of what is known about quarks has
been drawn from observations of what?
A: Hadrons.
Quarks have various intrinsic properties, including
what?
A: Electric charge, mass, color charge, and spin.
They are the only elementary particles in the Standard
Model of particle physics to experience what?
A: All four fundamental interactions, also known as fundamental forces.
What are the fundamental forces?
A: Electromagnetism, gravitation, strong interaction, and weak interaction
There are how many types of quarks known as flavors?
A: Six, up, down, charm, strange, top, and bottom.
Up and down quarks have the lowest what of all quarks?
A: Masses.
The heavier quarks rapidly change into up and down
quarks through a process of what?
A: Particle decay: the transformation from a higher mass state to a lower
mass state.
Up and down quarks are generally stable and the most
common in the universe, whereas strange, charm, bottom, and top quarks can
only be produced where?
A: In high energy collisions (such as those involving cosmic rays and in
particle accelerators).
For every quark flavor there is a corresponding type of
antiparticle, known as a what?
A: An antiquark, that differs from the quark only in that some of its
properties (such as the electric charge) have equal magnitude but opposite
sign.
The quark model was independently proposed by whom?
A: Physicists Murray Gell-Mann and George Zweig in 1964.
Quarks were introduced as parts of an ordering scheme
for what?
A: Hadrons.
There was little evidence for their physical existence
until what?
A: Deep inelastic scattering experiments at the Stanford Linear Accelerator
Center in 1968.
Accelerator program experiments have provided evidence
for what?
A: All six flavors.
The top quark, first observed at Fermilab in 1995, was
what?
A: The last to be discovered.
When was the quark model independently proposed by
physicists Murray Gell-Mann and George Zweig?
A: In 1964.
The proposal came shortly after Gell-Mann's 1961
formulation of a particle classification system known as what?
A: The Eightfold Way.
At the time of the quark theory's inception, the
"particle zoo" included what?
A: A multitude of hadrons, among other particles.
Gell-Mann and Zweig posited that they were not
elementary particles but were instead composed of what?
A: Combinations of quarks and antiquarks.
Their model involved three flavors of quarks, up, down,
and strange, to which they ascribed properties such as what?
A: Spin and electric charge.
The initial reaction of the physics community to the proposal was mixed.
Among the physics community there was particular
contention about whether the quark was a physical entity or what?
A: A mere abstraction used to explain concepts that were not fully
understood at the time.
Sheldon Glashow and James Bjorken predicted the
existence of a fourth flavor of quark, which they called what?
A: Charm.
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