Collisions at the LHC

While I’ve been away the Large Hadron Collider has been busy smashing protons together, and is now beginning to acquire some data that will be making some PhD students very happy. This is one of the images that has been released by CERN: (see


It shows a collision in the ATLAS detector  (the largest of the six LHC detectors – a cylinder approximately 46 m long by 25 diameter).  Two protons, each with 3.5 TeV of energy, have come in from opposite ends of the cylinder, and collided in the middle.  That energy has resulted in the creation of a plethora of other particles, which fan out from the collision point.  Their tracks are detected by a large 3-dimensional array of sensors, and are shown on the picture by the orange lines.  

You should be able to see that some of them are curved.  This is because the particles are charged. A charged particle moving in a magnetic field experiences a force, perpendicular to its direction of movement, and thus its path is altered.  By analyzing how quickly a particle curves in a known magnetic field, various properties can be deduced. Given that there have been no major headlines, I think it reasonably safe to assume that none of the particles created in this collision are anything out of the ordinary.  (i.e. no Higgs bosons). 

There will be an enormous number of such collisions produced – and the corresponding volume of data is fairly staggering – ATLAS can produce 50 000 gigabytes of data a second when collisions are occuring. This is a huge amount of data to analyze, and CERN have had to develop new computing solutions to cope.

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