A Quantum Diaries Survivor

Today was the first day of my course in subnuclear physics in Padova. I had given similar lectures in the past -to PhD students, both in Padova and in Catania- but I felt more responsibility this time, partly because I was going to discuss basic concepts of particle physics to students that had not had prior exposure to them.

The lecture I gave today was about the need for gauge symmetries, the lagrangian formalism for scalar and fermion fields, the issue of endowing with mass the bosons mediating weak interactions, and the connected problems of divergences and renormalizability. It was a fairly theoretical discussion, although I tried to give as much experimental perspective as I could to the various issues treated. I tried to make it quite clear just why one needs to insist that a lagrangian function retain local gauge invariance, and on the other hand why it is mandatory to add terms that at first glance spoil the invariance. I spent some time also describing the connection between observed and only hypothesized weak processes, their divergent behavior, the need for neutral vector bosons, and the resulting predictions of the GSW theory. The next lesson will start with the Higgs mechanism.

I was a bit worried before the lecture - I usually keep a cool mind in such occasions, but admittedly my knowledge of the theoretical nuisances below the surface of the simplified treatment I offered  in the lecture is not very deep. What worried me was not the chance of incurring in a tough question I was unable to answer - I have no trouble admitting my ignorance if that is the case- so much as the risk of embarking in a discussion of details which I would have explained in a less than satisfactory, inaccurate way: the responsibility of writing garbled physics concepts on the clean slates of my students’ minds. I have to admit I did not sleep well last night: but I prefer to ascribe that to my jetlag, and to Ilaria’s contribution -she woke everybody up at 4 in the morning with symptoms of a flu.

I did well. I recorded myself, and later analyzed the recording by noticing how much time I had spent on several topics, how repetitive I had been on some issues, and how clearly I had expressed the most important concepts. Overall I am mildly satisfied with the result. One thing I noticed, though, is that I have a mannerism in my speech, which consists in interspersing a sound like “errrr…” between sentences when I am thinking at what to say. I should just silence myself during those short, 1-second intervals. I will be working at that in the next lectures… Room for improvement there.

The next lesson will be the hardest for me, since the full theoretical formalism of the Standard Model will be explained in its details, and I will take care to derive a few important consequences for vector boson and Higgs phenomenology, and the shortcomings of the theory. From then on, I will start delving with the phenomenology of Higgs production and decay at colliders, things on which it will be much easier for me to produce a decent lecture. Following that, I will discuss top quark physics and other topics in hadron collider physics at the Tevatron and the LHC. I believe my students will also be happier with the latter part of the course…