A Quantum Diaries Survivor

Yesterday I spent the afternoon at a high school in Bassano del Grappa, where I held a 2-hour seminar about particle physics. The event was part of the program we have set up in Veneto this year for the Master Classes 2007 : students from the last years of high school get to attend a few seminars about XXth century physics and about the current research trends in particle physics, and then they visit the Physics Department in Padova where they are invited to measure some Z decay branching fractions using real LEP data.

There were only a dozen people attending my lesson, but they appeared extremely interested in what I showed them, and after two full hours of powerpoint slides and chalkboard graphs on the blackboard, they had the energy to ask quite a few questions, which I was of course happy to answer.

The comment from the teachers assisting the lesson was that I did a good job especially in showing how much I love the matter I explained to them. That, I think, is a strong message, which usually students do not fail to appreciate.

I of course also made a little advertising in the end, knowing that some of the students attending my lesson could end up becoming my collaborators one day. I encouraged them to come and visit me in Padova, and needless to say I had them write down the address of my blog

The subject of the lesson was quite simply, “Particle Physics“. I had to avoid discussing in detail particle detectors, which will be the subject of another seminar by a colleague, but I had basically a free hand in choosing the topics and the examples I would illustrate.

So here is what I discussed, in a nutshell. I started by enunciating four basic concepts that are fundamental in our field of research:

1. the importance of classification: I discussed Mendeleev’s discovery and how he could predict the existence of Germanium and Gallium from his periodic table; this was of use when later I showed that Gell-Mann’s quark model predicted the Omega-minus particle.
2. The tight coupling between technological advances and progress in our science: I made the example of Thomson’s discovery of the electron in 1897, only made possible by the cathode ray tube, invented only months before. I also discussed Rutherford’s experiment, to explain the importance of accelerators to probe matter at short distance scales. Here I took a chance to make a digression about the problems that religion and superstition cause to the advancement of science, giving examples of scientists burned at the stake, all the way to laws slowing down research on stem cells. I also had a word or three about the US budget and how it is shared between the department of Defence and the financing of scientific research.
3. The importance of spectroscopy: a mention of the discovery of the Balmer formula and its implication for the Bohr model, and the organization of energy levels and their use to identify atoms. This was later used when I discussed how physicists got convinced of the existence of quarks by discovering charm and looking at the Crystal Ball spectrum of charmonium states.
4. the Ockham principle - which had several uses in the description of what I showed later.

After the introduction, I discussed the hadron spectroscopy of the fifties, and the discovery of baryon number and strangeness. Strangeness introduced the quark model, which showed the predictive power of classification (the omega-minus). Recalling the Pauli exclusion principle allowed me to introduce the color quantum number. Then I showed how electrons were used to prove the structure of protons, and the charm discovery.

Having established quarks, I discussed the Standard Model in brief, and went on to discuss the top quark discovery, landing finally to talk about the searches for the Higgs boson, at LEP II, the Tevatron, and the LHC.

I think I did a fairly good job all in all. I avoided formulas in my slides, but then I found myself using the blackboard a lot to write down Feynman diagrams of particle decays… The audience was not scared.

You can get the powerpoint slides of my talk at this link , but beware, they amount to 11.4 Mbytes. And… too bad, but they are in Italian. One day I will translate them, if I happen to give the seminar outside my country.