In the LHC, particles are accelerated until they collide, releasing their energy in the form of many other particles.

My question is this: What happens to all those new particles and to the old particles that aren't destroyed in collision?
Do they dissolve in the nether, are they absorbed by the container, or are they simply so insignificant that they are left inside?


1 Answer 1


The collisions produce a shower of decay chain particles that impinge on the calorimeters (sensors that detect particle energy) surrounding the experiments. Particles in the beam that are not scattered every which-way by collisions can be diverted to a beam dump. Beam dumps are large targets, several meters long, that are designed to absorb the astonishing kinetic energy of the beam.

I recall during the CMS (Compact Muon Solenoid, one of the LHC experiments) talk broadcast today that the CMS calorimeter pixels have been noticeably degrading over time due to the high energy particles hitting them. This is probably because the incident particles are of sufficient energy to introduce crystallographic defects into the lead tungstate crystals used in the calorimeters.

  • $\begingroup$ The calorimeters are only one class of detectors (the ones designed to measure the energy of a particular group of particles). The pixel detectors are a different type (they provide high resolution position information but nearly no particle ID). Essentially all detector systems are subject to radiation damage and the business of keeping on top of this is called "gain monitoring". Both experiments reported impressive gain stability. $\endgroup$ Jul 4, 2012 at 19:56
  • $\begingroup$ @dmckee - Ah, my bad. Should I edit my answer to reflect this information? $\endgroup$ Jul 5, 2012 at 1:01
  • $\begingroup$ Up to you, your answer is basically fine. $\endgroup$ Jul 5, 2012 at 1:21

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