# Baptiste Ravina

PhD student - high energy physics
CERN/ATLAS/SUSY/TOP

1. ## PHY421 Particle decays and cross sections

These are notes from a PHY421 tutorial I gave today, essentially mirroring the discussion in Thomson’s Modern Particle Physics (first few sections of chapter 3) and in Prof. Costanzo’s lecture notes (I don’t have a working link yet - comment?).

2. ## PHY421 A word about the Dirac delta-function

There are already probably too many articles on the Dirac delta-function out there, but see if I care… More seriously, the following notes will just point out a few aspects of the famous function that might come in handy to the budding particle physicist. …

3. ## PHY251 Gaussians in Quantum Mechanics

Since this week’s QM problem sheets involves Gaussian integrals, I thought it might be a good idea to derive a few results of interest, rather than just stating them. Let’s then define the generic Gaussian integral : …

4. ## PHY251 Commutators in Quantum Mechanics

This post will be broken down into three parts : first, a few basics about commutators (for everyday use in physics), then the solutions to Problem Sheet 3, and finally an attempt at explaining the physical meaning of commutators (if you’re not a PHY251 student you might want to jump straight to that). …

5. ## QCD without the top quark? (Part 1)

Last week I introduced the basics of EFT from the perspective of renormalization; today, I’m considering a practical example : getting an EFT for QCD without the top quark, that is, trying to simplify QCD at energy scales $\lesssim m_t\simeq 172$ GeV. …

6. ## Beyond renormalization: a first look at EFT

I’ve started learning effective field theory (EFT), with a long-term view of finding possible applications to the experimental study of data excesses connected to simplified SUSY models and jet physics (substructure), my current areas of research. Here I want to lay out some basic concepts of EFT, as presented e.g. in Beneke’s notes; I might give a summary of the rest of the paper (which concerns heavy quark effective theory) in a subsequent blog post, as that seems like a good introductory example (or maybe even look at the Minimal Composite Higgs Model, following Ben Gripaios’ notes). …

7. ## More on Spontaneous Symmetry Breaking

Last week I talked about SSB and focused on its physical interpretation and effects, looking at fields and potentials while avoiding (as much as possible) to mention group theory. This is why I’ve decided to make the following into a separate post, where I’ll briefly re-emphasize a point I’ve already made in the last post (how we count massless modes in the broken theory) from a group-theoretic perspective. …

8. ## Spontaneous Symmetry Breaking : a crash course

Here I give a brief overview of spontaneous symmetry breaking (SSB) in the way I would present it to experimental particle physicists, assuming only little QFT background and barely even mentioning group theory. We will start with one-dimensional discrete symmetry breaking, extend it to continuous SB, mention Goldstone’s theorem and introduce the Higgs mechanism, before jumping to electroweak theory and obtaining the main result of interest : the generation of masses for the $W^\pm$ and $Z^0$ gauge bosons in the Standard Model. …

9. ## Gauge Lagrangian from differential geometry

Here I’m assuming some prior knowledge of QFT and the basics of differential geometry, and I will try from those basics to motivate the construction of the well-known Yang-Mills gauge Lagrangian : …

10. ## Writing LaTeX with Python

Let me jump right into it, and give you a (working) template code : …