The Discovery Machine: LHC

Scientific American

A Machine of Superlatives

To break into the new territory that is the tera­scale, the LHC’s basic parameters outdo those of previous colliders in almost every respect. It starts by producing proton beams of far higher energies than ever before. Its nearly 7,000 magnets, chilled by liquid helium to less than two kelvins to make them superconducting, will steer and focus two beams of protons traveling within a millionth of a percent of the speed of light. Each proton will have about 7 TeV of energy—7,000 times as much energy as a proton at rest has embodied in its mass, courtesy of Einstein’s E = mc2. That is about seven times the energy of the reigning record holder, the Tevatron collider at Fermi National Accelerator Laboratory in Batavia, Ill. Equally important, the machine is designed to produce beams with 40 times the intensity, or luminosity, of the Tevatron’s beams. When it is fully loaded and at maximum energy, all the circulating particles will carry energy roughly equal to the kinetic energy of about 900 cars traveling at 100 kilometers per hour, or enough to heat the water for nearly 2,000 liters of coffee.

The protons will travel in nearly 3,000 bunches, spaced all around the 27-kilometer circumference of the collider. Each bunch of up to 100 billion protons will be the size of a needle, just a few centimeters long and squeezed down to 16 microns in diameter (about the same as the thinnest of human hairs) at the collision points. At four locations around the ring, these needles will pass through one another, producing more than 600 million particle collisions every second. The collisions, or events, as physicists call them, actually will occur between particles that make up the protons—quarks and gluons. The most cataclysmic of the smashups will release about a seventh of the energy available in the parent protons, or about 2 TeV. (For the same reason, the Tevatron falls short of exploring tera­scale physics by about a factor of five, despite the 1-TeV energy of its protons and antiprotons.)

The kinetic energy of 900 cars traveling at 100 km per hour... 2,000 liters of coffee... It might not sound even all that much to some (even though those who can't imagine a car crash involving 900 cars traveling at 100 km/h need shooting or getting a life, a wife and a hobby) but it becomes even more mind-boggling when the incredibly small amount of mass involved in these experiments is actually considered.

Lemmesee, the total amount of protons involved is 3,000 bunches times 100 billion protons per bunch or 3 10¹⁴ protons (3 followed by 14 zeros).

Each proton has a mind bogglingly small mass of 1.7 10^-27 (zero, decimal point, followed by 26 zeroes and 17) kg, so the total mass is 5.1 10^-13 (zero, decimal point, followed by 12 zeroes and 51) kg. That's 0.000,000,51 milligram (mg) to you and me...

By accelerating these particles to almost the speed of light their rest-mass increases phenomenally and in collisions of particles traveling in opposite directions conditions are created of incredibly high energy density and temperature (much, much higher than the core of our sun) that approach the conditions that existed in the fire ball of the first millli milli milli seconds of the Big Bang.

Do you get it now?