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## Particle Physics: Learn With Fun : Part III – Quarks

In last two episodes, we learnt about What is Particle Physics?, Standard Model & Antimatters. Now Our aim is to learn about next step- Quarks. So are you ready?

# Quarks?

What are these?

In our earlier classes, we read about charge in such a way that it can’t be rationalised. That meant any charge can only be an integer multiple of electron’s charge i.e., 1.6 x 10-19 Coloumbs. But Quarks deny this concept.
There are six types of quarks, in three pairs:

•The Up quarks & • Down quarks
• The Charm quarks & • Strange quarks
• The Top quarks  & • Bottom quarks

## Extras

1. Kindly note that there are also six – antiquarks:

• Anti Up & Anti Down Quarks
• Anti Charm & Anti Strange
• Anti Top & Anti Bottom

2. Top- Bottom are sometimes called Truth- Beauty.
3. You should know that there is no existence possible of a single Quark. Quark extists as Quarks. These form composite particles after combining, called Hadrons.
4. As mentioned, Quarks, like protons and electrons, have electric charge. However, their electric charges are fractional charges, either +2/3 or -1/3 (-2/3 and +1/3 for antiquarks), and they always arrange to form particles with an integer charge (ie. -1, 0, 1, 2…).

Flavour Electric Charge
(e)
u up +2/3
d down -1/3
c charm +2/3
s strange -1/3
t top +2/3
b bottom -1/3

Because quarks join with each other to form particles with integer charge, (i.e. HADRON, what earlier mentioned) not every kind of combination of quarks is possible.

There are two basic types of Hadrons:
Baryons:

These are composed of three quarks

Mesons:

These are made up of a quark and an antiquark.

# Baryons

Examples of baryon are the neutron and the proton.

The proton is composed of two up quarks and one down quark. As you can see, in the image, when the charges from the individual quarks are added up, you arrive at the familiar charge of +1 for the proton.

The neutron is made up of two down quarks and one up quark.

Adding the charges from the quarks up, we arrive at zero.

# Mesons

An example of a meson is the pion.

The Pion is composed of an up quark and a down antiquark. Because mesons are a combination of particle and antiparticle, they tend to be very unstable and decay very quickly.

So this was about Quarks!! Next article will be about counter friend of quarks- called Leptons. Enjoy, Share & Comment.

## Dark Matter

A typical galaxy contains much more matter than what we can actually see. In fact, the visible portion of a galaxy represents only about 5 to 10% of total mass of the galaxy. Many studies lead us to define the conclusion that the Universe abounds in matter that we cannot see. This unseen matter is called Dark Matter because either it does not emit light or its light emission is too dim for us to detect.

Normal matter, such as STARS, PLANETS, DUST and MOLECULES , is often called Baryonic Matter because its mass is primarily due to the combined mass of the protons and neutrons, which are combinedly called Baryons, it contains. The mass of electrons is neglected because the mass of an electron is so small relative to the mass of a proton or neutron. Some of the normal matter such as burned out stars and dim interstellar gas, is part of the dark matter in a galaxy.

However, according to various calculations, this dark normal matter is only a small part of the total dark matter. The rest is called Non Baryonic Dark Matter because it does not contain proton and neutrons. What it contains? We know only one member of this type of dark matter…..the neutrinos.