The Standard Model
Below is complicated diagram of what can be a complicated discussion. But unless you’re a budding physicist you don’t really need to understand every particle spin, interaction and result to understand the broad concepts we’ll be talking about on this site. And I’m quite convinced that it is the intentional convoluted naming convention (and lack thereof) that makes particle physics somewhat challenging rather than the concepts it tries to explain.
This article then, is intended to familiarize the uninitiated with the terminology of the basic sub-atomic particles in the standard model. Maybe it will help you get through your next read of a scientific journal article, or maybe just a cocktail party with your favorite particle physicist. In any event, hopefully you’ll know more than 90% of the world population after reading this simple introduction.
If you will indulge my memory device, though corny as most of them are, it is effective and has enabled students to remember the fundamentals after just one review.
When looking at the diagram, keep in mind this simple set of facts: There are two types of building blocks to the physical universe, bosons and fermions.
- Bosons are the particles that are responsible for the forces described by the standard model.
- Fermions are the particles that make up matter.
- Fermions exchange bosons to interact.
To solidify that most fundamental of all facts (from what is known today!) and its terminology in your mind, You may want to think of the Fermilab particle accelerator in Chicago that I happen to know has free range bison grazing its grounds. Bison are powerful (forceful) animals located throughout the Fermilab campus (a real place with a physical structure composed of matter).
The Four Forces
Gravity – the most common sense and observable force in everyday life is not explained by the standard model. We’ll be covering that massive hole in human knowledge and what’s being done to remedy it on other pages in this section. For now let us focus on the forces that are predicted and explained by the standard model.
Electromagnetism – light, magnets, electricity etc. This one’s easiest to remember. It affects the charge of protons and neutrons and allows them to attract to form atoms. You may not have known that the actual force is carried by the photon. When two electrons interact, they repel each other, exchanging photons. The electromagnetism force has Infinite range.
Strong (nuclear) Force – Holds the building blocks of matter together, strong but short range. If we extend the metaphor of the physical structure of Fermilab being constructed of Fermions, we’ll say it is made out of Quarks (think odd-shaped bricks), and the force that holds it together is still the bison (boson), but only the bison’s very strong hide processed into glue (the gluon).
Weak (nuclear) Force – Responsible for various kinds of radioactive decay. Staying with our bison/Fermilab metaphor, let’s say that the people of all shapes and sizes inside the Fermilab structure represent all sorts of particles. The Wily bison Zealously maintain their presence around the structure, forcing weak people (particles) and their puny energy out of the structure (radioactivity). The bosons responsible for this force? Why the Wily “W” and the Zealous “Z”, of course.
Here’s our Story
And we’re sticking to it!
Fermilab, constructed of odd-shaped bricks is strongly held together with bison-based glu on them, and is surrounded by Wily, forceful bison who Zealously force weak people with their little energy to leave.
Fermion quarks have physical mass and are held together by the strong force boson gluon. The W and Z bosons are responsible for the weak force radiation as particles leave an atomic structure.
Protons, Electrons, and Neutrons (oh my!)
Protons, electrons, and neutrons, as I’m sure you were taught in high school, are the basic building blocks of atomic-level matter. You remember, the elemental chart? Let’s put together our knowledge of subatomic particles to get to the real matter (pun intended).
Going back to our complicated-looking particle chart, we understand what the W & Z and gluon bosons do (weak and strong forces respectively), and that matter is made up of fermion quarks. We haven’t covered any of the fermion leptons so we’re about to find out what that tiny, most useful of all leptons does, the electron.
Very nearly everything in the physical (i.e. touchable) universe, including you, is made up of just three fermions, two types of quark and a lepton, the electron. There are several more fermions, but these three matter particles comprise nearly all of the mass in our known universe and will suffice for this lesson.
The two most prevalent quarks are known as ‘up’ and ‘down’. And when viewed along side the electron, all three possess a unique electrical charge important to how they combine to create the basic building blocks of an atom:
- Up quarks carry a positive two thirds charge (+2/3).
- Down quarks carry a negative one third charge (-1/3).
- Electrons carry a ‘whole’ negative charge (-1).
Depending on how these three quarks combine, you can get a particle with a whole negative charge (the electron), a whole positive charge (the proton), or no charge at all (the neutron). A bit of simple math shows us how this works.
- Electrons are a fermion lepton, not made up of anything smaller. With a full negative charge that is (-1) + (nothing) = -1
- Protons are made of two up quarks (+2/3) + (+2/3) =+4/3 and one down quark (-1/3). Add the negative third charge of the down quark and you get a particle with a full positive charge (+4/3) + (-1/3) = (+3/3) =+1
- Neutrons are made of two down quarks and one up quark. Adding these together we see that the charges cancel each other out and we get no charge at all: (+2/3) + (-1/3) + (-1/3) = 0.
So there we have it. Three basic particles, a proton with a full, positive charge (+1); an electron with a full negative charge (-1); and a neutron with no effective electrical charge.
Various combinations of these three particles pretty much make up all matter in our physical universe – things that have mass and can be touched. One electron circling a single proton makes hydrogen, the most basic atomic structure and the most abundant element in the universe. All you have to do to get every other element conceivable, simply add protons, neutrons and electrons!
For the astute, or for those who are gluttons for punishment, you will have noticed that we completely skipped the odd-hanging Higgs boson shown on our diagram. Incorrectly shown with a question mark next to its mass, scientists confirmed it existence since the chart was drawn. Rather than being the oft-touted god particle, its a rather innocuous particle, the ramifications of which will be dealt with in another article. Once I get over the huge personal disappointment of this lackluster discovery.
Intro Video before the Higgs was discovered.
Silliest, yet most straight forward description of the Higgs Boson
Without all the nonsensical god references. Physicist believe the Higgs gives the other particles Mass. Referring back to our standard model at the top and the video you’re about to watch, Justin Beiber is a Quark and the teenaged girls are the many Higgs floating about in space.