Anatomy of a Particle Physics Experiment

Recently I returned from a particle physics experiment at the Paul Scherrer Institut, a nuclear research lab in Switzerland. I was one of ten students from the University of Heidelberg and ETH, Zürich who had two weeks of (nearly) free reign to carry out an experiment on the PSI’s proton beam line. To put into perspective how crazy that is, ordinarily the going rate for such a privilege is €10,000s per day!

Our goal was to measure a mysterious number called the “Panofsky ratio”. The ratio is named after Wolfgang Panofsky, first to attempt to measure it, and corresponds is the relative likelihood of two events involving particles called protons and pions occurring. It is important, because historically its value strongly contradicted the expectation of theoretical physicists. The two processes occur by means of two different forces — one by the weak interaction and the other by QED — and so the ratio was expected to be somewhere near the ratio of strengths of these interactions, give or take a few corrections, which happens to be around 30 Continue reading

Solving the Schrödinger Equation with Numerov’s Algorithm

The Schrödinger equation describes the energy and time-evolution of a particle or system of particles, and is one of the fundamental building blocks of modern physics. In it’s general form, the (time-independent) Schrödinger equation looks like this:

\(\frac{-\hbar^2}{2m} \frac{\partial^2}{\partial x^2}\psi(x) + V(x) \psi(x) = E\psi(x)\)

There are relatively few situations in which the Schrödinger equation can be solved analytically, and numerical methods and approximations are one way around that analytical limitation. To demonstrate how this is possible and how a numerical solution works, what better way than to solve a system which can be solved analytically and comparing the results. Continue reading

Physics Bungee-Rope Cursor Trailer

I’m getting ready for starting a course in computational physics, and so, ignoring the fact I’m meant to be revising for an exam this Monday, I thought I’d prepare for the more exciting of the two. I’ve always wanted to code this little physics model ever since I saw it on one of those JavaScript snippet websites back when dial-up was fast and people downloaded mp3s one at a time. Those were the days.

Well, I never made it mainly because I didn’t understand how. Could this be the best thing my physics degree has taught me thus far? Continue reading