Archive for November, 2009

COLLISIONS!

So as you may well be aware, the LHC started up again this weekend after a good 14 months off.
September 10th last year was the date penned for the long overdue startup of the Large Hadron Collider – the worlds biggest (and best) particle accelerator. Unfortunately a problem with the cooling system caused a leak of liquid helium and a saftey mechanism called a quench kicked it. It basically ruined a few magnets so the whole thing had to be shut down to be fixed.

Well, it was fixed, and this weekend saw the grand reopening. On Friday evening, the various LHC control rooms were full of physicists and excitement as the beams were reinjected into the machine. First one way around, then the other. The plan, as us postgrads understood it, was that collisions (ie, two beams in the LHC going in opposite directions and brought to a focus at the detectors) were not due until early December.
Well, we were wrong. Today (the 23rd November), the LHC injected beam 1 into the LHC, then injected beam 2 and started ‘beam synchronization’. I don’t fully understand what that means, but I know that there was one bunch per beam (about a metre in length worth of protons), and my best guess at ‘beam synchronization’ is that the two bunches were brought close together.
Obviously the beams weren’t focussed and we weren’t running at anything close to design luminosity, but a few collisions occured in all 4 detectors. An exciting moment for everyone involved with the LHC, indeed.

The CERN Press Release of the weekend’s events and a summary of the collisions explains a bit further what the goings on were this weekend, and what the plans for the LHCs immediate future are.

The coming months should be an exciting time for particle physics, and the coming years will hopefully shed some light on the darker corners of the Standard Model and beyond…

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New Recordings

New versions of Down the Rabbit Hole and Advice from a Caterpillar are now up!
Recordings of Pig and Pepper and A Mad Tea Party will be made shortly :)

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Feynman Diagrams that look like animals

In Particle Physics, there is a special tool that is used to help understand, visualise and calculate certain aspects of a particle interaction. This is the Feynman Diagram.

A lot of Feynman Diagrams are fairly dull, monotonous affairs, essentially consisting of two particles scattering off each other, like so:
feynman

However, there are some Feynman Diagrams which can, with the help of a little imagination, be made more exciting!
Recently, I discovered that, if I stare too long at Feynman Diagrams, I start to see the diagram in a different way, much like how you can often see faces while staring at a plastered ceiling, or see shapes in the clouds.

I see animals in Feynman Diagrams.

Here’s a few to get you started.

Now, any High Energy Physicist will tell you that this has already been done, in the form of the Penguin Diagram.
penguin
Which, if you squint a bit, can look a bit like a penguin. (The animal, not the chocolate bar)
penguin2

The Penguin Diagram originated when a bet between Physicists was made, the loser of which had to include the word ‘Penguin’ in their next paper. So it’s all a bit artificial really…

Next, the deer diagram. It’s fairly self explanatory, the gluon emitted by the up quark represents the antlers, the rest follows from that…
deer

The fish diagram. This one takes a little bit of thinking, but not too much. Obviously the top quark pair production vertex is the ‘nose’ of the fish, the bottom and anti-bottom quarks are the main fins of the fish and the quark antiquark/lepton antilepton pairs are the tail fins.
fish

The lobster. This one, I’ll admit, is a bit contrived. But bear with me. The quark antiquark/lepton antilepton pairs at the very right are obviously the claws. Where the quark and anti-bottom lines form a diamond with the top anti top pair is the head, the gluon is the body (albeit a very skinny body considering the size of the head), and the protons at the left are the tail.
lobster
Well, it’s either a lobster or Edward Scissorhands on his side with his arms upstretched…

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