High energy alien particles hit the sky above us every minute. We can’t see them, but they can be detected by exploiting an interesting bit of physics: the Cherenkov light produced as they zip through a medium faster than the speed of light.
The art of tracking particles is literally at the heart of the big LHC detectors. It is an enormously complicated 3-dimensional join-the-dots exercise. This challenge requires advanced software, developed by teams of programmers over many years. This is a story of how I figured it out one summer.
Fifteen years ago, I was a postgraduate physics student at Oxford, working on a dark matter search experiment, when I first read Philip Pullman’s His Dark Material’s trilogy. It was quite a thrill when I reached the part where Lyra walks into our lab to learn what it is, and how we search for it. Here is my perspective on that scene in this epic fantasy.
Silicon – the favourite element of the electronics industry – also has an important role in particle detectors allowing us to pin down the tracks of the hundreds of particles produced by collisions at the large hadron collider. As planned upgrades of experiments will need detectors with even better resolution and durability, we are investigating various ideas for new silicon detector technology.
Dark matter has long been a popular subject choice for a public talk on particle physics or astronomy. Not only is it genuinely one of the biggest mysteries in modern science, but it is also a great story. The astronomical evidence that the majority of the galaxy is made from some unknown invisible substance is overwhelming. The theory that this missing matter consists of a new type of particle is the frontrunner explanation. It falls to particle physicists to test this hypothesis by searching for dark matter particles—a challenge which we accept with relish.
Experimental particle physics has seen some quite spectacular blunders. In 2008 the Large Hadron Collider was turned on, with the world’s media watching closely. Nine days later a manufacturing fault caused a superconducting wire in a magnet assembly to become non-superconducting. As 13,000 amps of current suddenly encountered resistance, the temperature shot up, an electric arc damaged the liquid helium enclosure, and as two tonnes of liquid helium became non-liquid the resulting explosion destroyed 53 magnets and delayed the project for another year while this was repaired. Oops.
The Fermilab particle physics laboratory, an hour’s drive west of Chicago, is the home of an experiment with the wonderfully nerdy three-character name of g−2 (“gee minus two”). It is built with a single purpose: to measure the g−2 factor, which, as the name implies, is the result of the simple arithmetic of subtracting two from g, which, when multiplied by a scaling factor, gives 116 591 802…