Week of October 16

Congratulations to my mentor! He and his wife had a baby boy this past week, so he won't be coming in for the next two weeks. However, I still went to Siena to answer some of the study questions he'd given me and to work on my Python skills.

Here are the study questions I answered:

 

What are quarks?

A quark is an elementary particle that is believed to be a fundamental constituent of matter (it serves as a sort of “building block” for matter).

Quarks, which are never found in isolation,  make up composite particles called hadrons, which include protons and neutrons.

Antiparticles of quarks are called antiquarks, and they have the same general properties of quarks except their charges have the opposite sign.

Flavors of quarks:

Up (u): + 2/3

Down (d): -1/3

Strange (s): -1/3

Charm: + 2/3

Top (t): +2/3
Bottom (b): -⅓

Properties of quarks:

Electric charge

Spin (form of angular momentum; can be visualized as the rotation of an object around its own axis)

Weak interaction: A quark of one flavor can transform into a quark of another flavor only through the weak interaction. By absorbing or emitting a W boson, any up-type quark (up, charm, and top quarks) can change into any bottom-type quark (down, strange, bottom) or vice versa.

Mass

Color charge and strong interaction:

Quarks have electromagnetic charge, but they also have a completely different type of charge called color charge. The force between color-charged particles is called the strong interaction force. The strong force holds quarks together to form hadrons, and its carrier particles are called gluons.

While quarks have color charge, composite particles made out of quarks have no net color charge (they are color neutral). As a result, the strong force only takes place on the really small level of quark interactions.

What are gluons?

Gluons are elementary particles that act as the exchange particles for the strong force between quarks. Gluons themselves carry color charge, and therefore participate in the strong interaction in addition to mediating it.

Quarks carry three types of color charge (blue, red, and green) and antiquarks carry three types of anticolor (antiblue, antired, and antigreen). Gluons can be thought of as carrying both color and anticolor.

Since the force-carrying gluons have a color charge, they participate in strong interactions. As a quark-antiquark pair separates, the gluon field forms a narrow tube (or string) of color field between them. This tube of color field means that there is a strong force between the quark pair that remains constant, regardless of their distance.

What are mesons?

Mesons are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. All mesons are unstable, and charged mesons decay (sometimes through intermediate particles) to form electrons or neutrinos. Mesons are not produced by radioactive decay, but instead appear in nature only as short-lived products of very high-energy interactions in matter, between particles composed of quarks.

Each type of meson has a corresponding antimeson in which quarks are replaced by their corresponding antiquarks and vice-versa. For example, a positive pion (π+) is made of one up quark and one down antiquark; and its corresponding antiparticle, the negative pion (π−), is made of one up antiquark and one down quark.

Mesons participate in both weak and strong interactions.