Mel Shochet on designing particle detectors.

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Mel Shochet on designing particle detectors.

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Yes and no. Yes in that the physics was crucial and if you ignore the physics you shouldn't be working on the trigger. No in that we realized pretty early on that we couldn't know what the physics was going to be like. At least we hoped we didn't know, I mean the hope was that we were going to find things that no one anticipated. So you had to design something that in fact was quite general and quite flexible, so that if you started to see a hint of new physics you could alter the system to focus on that.

So what we decided to do quite early is to try to focus on the elementary partons that would be the decay products of anything new. So electrons, meuons, jets, which meant quarks and gluons, missing ET for neutrinos. And the goal was as generally and as quickly as possible, to try to find all of these objects and to make lists of them. Here are all the electron candidates with their energies, the directions that they're pointing, here are all the jets, their energies, the directions they're pointing, the meuons, the missing ET.

And once you construct that list, then that could all be done in dedicated hardware with enough handles so that you could fine tune the way you found jets, and your minimal requirements on electrons. But essentially an algorithm that was predetermined. Then once you make the list you allow a very fast but programmable device to make the final decision of what it is that you are interested in. So do you want events with one high energy electron, if so, how high energy, is there anything else that you require to go along with that, like missing energy or jets or meuons? That provided the flexibility.

If there was some new object that no one had even imagined, that decayed into a meuon and an electron and two jets, this allowed the flexibility. Once you started to get the hint of that to focus on it. And so it wasn't completely built in hardware but enough was built in hardware so that it would be fast because it had to be fast enough so that we wouldn't incur dead time, and that meant making a first decision in under six microseconds as it was initially designed.