Big Bang Day

Given that I spent last week locked in Somerville anticommuting gamma matrices, you've probably seen more of the publicity than I have, but in case you missed it... tomorrow (Wednesday) has been dubbed "Big Bang Day". This is a media event when first circulating beams are injected into the LHC. As I'm working on ATLAS, one of the four-ish detectors that will get the results, I'm eagerly anticipating first collisions.

However, that won't happen for a some weeks to come, once we have beams in both directions and they can be squeezed down and collided, so I'm a little embarrassed by the media interest in the switch on. They wanted a day that could be arranged in advance, and aren't sure how quickly they'll be ready for collisions (there will be an official opening on 10th October). All this means that if you believe that black holes, or strangelets, or whatever will destroy Geneva/the world/the universe, then you have a little longer to enjoy your last days. Probably you needn't really worry until the energy is increased from 1 to 10 TeV, since the Tevatron has been running for years at 2 TeV - and we are still here.

Anyway, I thought this would be a good time to post some nice ATLAS/LHC links I've collected. These are all aimed at the general public (I wouldn't try to bamboozle you with science):

• LHC First Beam including live webcast
  
• BBC Radio 4 Big Bang Day. I'm looking forward to the radio episode of Torchwood at CERN.
  
• A nice explanation of why the LHC won't destroy the world. I liked this because they'd thought of more ways that the LHC might destroy the world that I hadn't thought of - and then demolished them.
  
• Time lapse video of the ATLAS construction - this really is hypnotic
  
• The Large Hadron Rap explains everything
  
• Newsnight Scotland item on last year's ATLAS meeting in Glasgow. A reasonable summary, but I like this one because I was at that meeting (the last full ATLAS meeting in the UK). I'd had dinner with the interviewee (Craig Buttar) just before he went on air.
  
• Some YouTube groups: LHC UK (John Barrowman and lots of Brian Cox) and ATLAS
  

Cool fact (among many you can find in links above, but it was one I didn't know before a talk I went to last week): At full energy and luminosity, the LHC beams have 362 MJ each, equivalent to 80 kg of TNT. That doesn't sound earth shattering, except the point is they are squeezed to 17 microns - the width of a human hair (and 27 km long).

First event seen by ATLAS

The first "beam-gas" events seen by ATLAS.

These look rather messy because this is a collision between the (single) beam and a residual gas atom in the beam pipe. As soon as we get colliding beams, beam-gas events will mostly be background that we'll want to exclude - which is why an extreme vacuum in the beam pipe is so important.

The available ("centre of mass") energy in a collision with a stationary atom is much much less than colliding with another counter-rotating beam (a quick calculation for this case gives a factor of 400,000 less).