Elementary Particles

And Their Properties

M.Zeeshan Khalid

09050610-039

Elementary particles

• Introduction

The most fundamental constituents of our universe are the

elementary, or fundamental particles. They are the "building

blocks" that make up everything in the universe. Though their

most basic nature is still being debated, most of these particles

have well-documented, experimentally verified properties.

Listed here are the most important of those properties.

However, many aspects of cosmology are still being

developed, and additional elementary particles of higher mass

may be discovered in the near future with the next generation

of particle accelerators.

The Structure of Matter

• The Structure of Matter The elementary particles known today are divided into three families.

All "everyday" matter is made up of atoms, once thought to be the smallest division of matter.

atoms have a substructure in their own right - they are made of a negatively charged electron cloud surrounding a positively-charged nucleus.

The nucleus in turn can be divided still further into positively charged protons and neutral neutrons.

A proton is made of two up-quarks and a down-quark, and a neutron is made of two down-quarks and an up-quark.

Cont…

e. Protons are made of two up-quarks of electric charge 2/3 each, and one

down-quark of electric charge -1/3; these charges add together to produce

an overall charge of 1.

Neutrons consist of two down-quarks of -1/3 each and one up-quark of 2/3; these cancel out to an overall charge of 0. Thus, the atom itself is neutral.

The Family Tables

The following tables summarize most of the properties of the various

particles belonging to the three families of subatomic particles. The

properties listed here, along with the name of the particle, are: mass,

electric charge, strong charge, weak charge. The strong charges of quarks

have been creatively designated red, green, and blue by physicists; they do

not, however, actually have color - they are too small for light waves to

bounce off. A particle's mass determines how it responds to gravity, the

electric charge determines its response to electromagnetism, its strong

charge determines its response to the strong force, and its weak charge

determines its response to the strong force.

Family 1

Particle Mass Electric Charge Strong Charge Weak Charge

Electron .0054 -1 0 -1/2

Electron-Neutrino

<10-8 0 0 1/2

Up Quark .0047 2/3 red, green, blue

1/2

Down Quark .0074 -1/3 red, green, blue

-1/2

Family 2

Particle Mass Electric Charge Strong Charge Weak Charge

Muon .11 -1 0 -1/2

Muon-Neutrino <.0003 0 0 1/2

Charm Quark 1.6 2/3 red, green, blue

1/2

Strange Quark .16 -1/3 red, green, blue

-1/2

Family 3

Particle Mass Electric Charge Strong Charge Weak Charge

Tau 1.9 -1 0 -1/2

Tau-Neutrino <.033 0 0 1/2

Top Quark 189 2/3 red, green, blue

1/2

Bottom Quark 5.2 -1/3 red, green, blue

-1/2

Fundamental Forces:

There are four fundamental forces in the Universe:

1. gravitation (between particles with mass)

2. electromagnetic (between particles with charge/magnetism)

3. strong nuclear force (between quarks)

4. weak nuclear force (operates between neutrinos and electrons)