What does 7TeV mean?

NA49: lead-lead collisions
(Credit: CERN)

Particle physics measures energy on a really small scale using a unit called electron-Volts (eV). This is because it is closer to the energies of the particles that particle physicists investigate. Normally we use Joules as the unit of energy (An average man needs 10,000 Joules a day) but this amount is truly huge compared to the energies of tiny particles.

1eV is 1.6x10-19 Joules! That’s 0.00000000000000000016J!

7TeV means 7 Tera electron-Volts (Where Tera just means Trillion, or 1x1012), therefore 7TeV is roughly a Billionth of a Joule (1.12x10-6J). This may seem like a small number but just wait!

LHC pipeline
(Credit: CERN)

The Large Hadron Collider (LHC) particle accelerator in Switzerland generates two beams of particles travelling in opposite directions, each containing thousands of bunches of protons. Every little bunch of particles contains approximately 100 Billion protons, each with 7 TeV of energy! Some quick maths tells us that every bunch then contains 112,000J! That’s enough energy to move a small passenger jet at walking pace!

CMS: Higgs boson decays to four muons
(Credit: CERN)

If we take a bullet fired from a rifle as an example we can compare energy levels; a bullet typically weighs about 4 grams and can travel at about 1,000 meters per second when it leaves the barrel. Using the kinetic energy equation, we get a total energy of 2,000J, making a bunch of protons going around the LHC 55 times more powerful than a bullet!

To create a single electron you need 511,000eV, meaning that you could potentially make 30 Million electrons just from the combined energy of two of the protons colliding at the LHC!

Science and Technology Facilities Council Switchboard: 01793 442000