The LHC and particle physics

BBC News: Particle beams injected into LHC.

Engineers working on the Large Hadron Collider (LHC) have successfully injected beams of particles into two sections of the vast machine.  An LHC spokesperson said this was the first time particle beams had been inside the LHC since it was shut down late in September 2008.  Scientists working on the giant particle accelerator described the success as "a milestone".  They plan to circulate a beam around the 27km-long tunnel in November.

The Large Hadron Collider is using protons and lead ions at a paltry 450 billion electron volts, or 0.45 TeV (tera electron volts), the goal is to get the beams up to 7TeV in 2011, which will mean two beams colliding at a total energy of 14TeV.

A hadron is a class of particles made from multiple quarks.  There are two types of hadrons, mesons, which are made of one quark and one antiquark, and baryons, which are made of three quarks.  You are made up of baryons, because the two most common baryons are the proton and the neutron, which make up atoms, which group into molecules, which group into people and other useful stuff, like cheese, and lizards, and CD players.

Quarks never travel alone, they always form hadrons.  Even when you smash the hadron, you won't knock a solo quark off it, though if you're lucky you might jumble the quarks up into new, short-lived particles.  Quarks come in six types known as flavours which has nothing to do with taste, for the same reason electrons have a property called "spin" that has nothing to do with physical rotation, and quarks possess a property known as "colour" that has nothing to do with how they look.  Just go with the madness.  The six flavours are:

  • up
  • down
  • top (also knows as "truth")
  • bottom (also known as "beauty")
  • strange
  • charm

Protons and neutrons are made from up and down quarks, making them the most common.  The last quark to be found was the top quark, and it's massive compared to the others.  But the strange quark is the one people are worried about.  In theory there's an infinitesimal chance the LHC could create "strangelets" made from up, down, and strange quarks.  They'd be unstable (which means the strange part would go in a tiny fraction of a second), but if they touched a piece of normal matter, it might convert to strange matter.  Chain reaction, our planet turns into a blob of strange goo and we all die.  In practise, if this was going to happen, it probably would have done so at RHIC, the Relativistic Heavy Ion Collider at Brookhaven in New Jersey, which has been running since 2000 and happily smashing protons, and ions of deuterium, gold, and copper together.

As an aside, we may be running low on helium.  Amarillo, Texas is the helium capital of the world, holding the world's largest reserves, and those reserves are running low.  Helium is essential for many superconducting experiments, and the LHC and RHIC depend on it.

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