Let's try that again

It's been suggested that if you go to send someone a "Happy New Year" message and notice that the last one you sent was the same thing last year, that maybe you don't need to send the message. Well, I'm going to try to prove that wrong and once again kick start this blog.

My writing in 2018 was hamstrung partly by illness. I had much better excuses last year, which was actually much worse. But this blog is called "Real Self Energy" and I am always trying to look on the bright side and see the positives, so if we look at what I was looking forward to last year in physics, in fact this year we could say almost exactly the same things:

1. We're still waiting for the results on muon \( g-2 \). At the French intensity frontier GDR meeting in November we had a great talk on this by Marc Knecht, and the theory challenges in the future, which really convinced me that theorists do have a good handle on the calculation and we are just waiting for the experiments to have their final say.
2. The B-meson anomalies lost a bit of their lustre with an update that just preserved the status quo: the measurement of \( R(K) \equiv \frac{\mathrm{BR}(B \rightarrow K \mu \mu)}{\mathrm{BR}(B \rightarrow K e e)}\) by LHCb moved closer to the Standard Model value while the uncertainty shrank, keeping the deviation about the same, while a preliminary measurement by Belle of \( R(K^*) \equiv \frac{\mathrm{BR}(B \rightarrow K^* \mu \mu)}{\mathrm{BR}(B \rightarrow K^* e e)} \) was consistent with the SM value, but with much poorer uncertainty than the (anomalous) values from LHCb. Again we discussed this extensively at the GDR in November and there is still a lot of excitement and anticipation that looks set to continue for some time, with many experiments set to report data over the coming years. A good reference of the current status is this paper.
3. The CMS and ATLAS collaborations seem to be taking their time with analyses of the full dataset of Run 2, so we are still waiting for lots of new results to come out. From the theory perspective, I have recently been involved in putting collider limits on new theory models ("recasting") and every time new experimental results come out, there is a lag before they are implemented in the various theory tools. One of the interesting questions for me will be which theory tool emerges as the winner in the long run from this effort, or if the experiments will first make their analyses completely unreproducible (e.g. by moving from cut-based analyses to neural networks)!
4. Regarding the Higgs, the mass has already been experimentally determined to an accuracy much better than we "need" (compared e.g. to the top quark), and the accuracy of the coupling measurements will only be incrementally improved with more data. There has been a lot of interest in the production cross-section, for both single and double Higgs events, where I learnt recently that the prediction in the Standard Model is now more accurately known than it can ever be determined at the LHC. This is an interesting effort that one of my LPTHE colleagues got into last year: here and here.

None of this mentions dark matter, neutrinos or axions, where there are lots of interesting things going on. And I was going to mention last year's politics, but I have run out of time for today, and, since that's a rather personal and bleak post, I will leave it for later!