I once was an active chessplayer, but work duties have long taken tournaments off my plate - I simply do not have the time to sit through long hours of chess battles. So I play blitz online on chess.com (my handle is "tommasodorigo", in case you wondered).
Supersymmetry, the extension of the Standard Model of particle physics that was once sold as an almost certain discovery that the LHC experiments would bump into upon starting to collect proton-proton collisions, is not in a very healthy situation these days.
In 1992 the top quark had not been discovered yet, and it did not make much sense for the CDF collaboration to have a full meeting devoted solely to it; rather, analyses targeting the search of the top quark were presented at a meeting which dealt with both bottom and top quarks. This was called back then "Heavy Flavour meeting".
Two days ago I wrote a quick post to stimulate non-flat-EEG readers to consider an apparently trivial question, which in fact hid many subtleties. The general question I wanted to address was whether an estimate missing an uncertainty was more or less useful than a quoted uncertainty on the same parameter when the estimate itself was missing.
With the Higgs boson in the bag, the game called "global fit" that particle physicists have been playing for a couple of decades has changed significantly. The knowledge of the Higgs boson mass provided by the measurements obtained by the ATLAS and CMS experiments, added to dozens of other measurements of critical observable properties of subatomic particles that have been measured at LEP/SLC, LEPII, the Tevatron, and the LHC itself, allow us to constrain some of the fundamental parameters of the Standard Model more than direct experimental determinations do.But what the heck is a global fit ?
ATLAS has just produced a very nice new study of jet production in Z-boson events. I will describe a sample graph below, but before I do I find it useful to explain to the less knowledgeable among you what a hadronic jet is, just in case you've been away during the last forty years.Hadronic Jets: what are they ?
One of the most intriguing effects in subatomic physics is the phenomenon of violation of the discrete symmetry called "CP". It is intriguing at various levels. First of all, CP violation is intriguing because of the depth of the concept: proof of that be that it is not at all easy to explain it to outsiders (I will make an attempt below, but I am likely to fail!). Second, its elusive nature makes it even more mysterious and difficult to study: only a few subatomic physical systems exhibit it, and the effect is visible only as a modification of measurable quantities at the level of a few parts in a thousand.
Pictures showing the structure of matter and the organization of subatomic particles in different categories abound. Indeed, cataloging and classifying entities subject of study is a powerful means of grasping their essence and infer their properties. The most striking example I can offer is the Mendeleev table of elements (which allowed its creator to spectacularly deduce the existence of elements not yet discovered); but there are many others, like the Hertzsprung-Russell diagram of star classification, or the one for galaxies, or the cataloging of animal species...
Now that the Higgs has been found, the current hype in popular science magazines suggests that the most pressing question in fundamental physics research is whether new particles will be found at the Large Hadron Collider: Is Supersymmetry the right extension of the standard model? Or are there new extra dimensions of space-time ? Can microscopic black holes be created in particle collisions ? I think all of you have heard some of these questions enough times by now.
The T2K Collaboration released today an analysis of their data in the Cornell Arxiv. T2K searches for electron neutrinos appearing in a muon neutrino beam produced by the J-PARC accelerator facility in Tokai-Mura, using a near detector located 280 meters downstream of the proton target, and a far detector (SuperKamiokande) at 295 km from the source. The appearance of electron neutrinos in a muon neutrino beam is a very important oscillation signal of neutrinos, that allows the measurement of the parameter theta_13, one of the so far less-well known parameter of the neutrino mixing matrix.
The mediatic effect of the Higgs boson discovery of last July is clear to everybody. And CERN has been very good at exploiting it, making fundamental physics a familiar topic and creating interest worldwide. Yet I think we can do more. The gap between basic research in physics and the public is wide, and we are doing still too little to fill it.
What looks like a tantalizing signal of the rare two-muon decay of the Higgs boson has been evidenced in an analysis of 2011+2012 data just sent to PRL by the CMS collaboration. This analysis targeted supersymmetric neutral Higgs bosons, whose decay to muon pairs is enhanced for some values of the SUSY parameters, but was not expecting to see any signal in the 25 inverse femtobarns of collisions that the CMS experiment has so far collected.
I think I wrote a post about the "definitive results" of the CDF and DZERO experiments on the search for the Higgs boson at least a couple of times already in the past, but you know, these busy experimentalists continue to improve their analyses, adding previously incomplete information, combining results, tweaking and improving things here and there. It is only natural that on such an important topic as the observation of the Standard Model Higgs boson the Tevatron folks were not ready to give up just yet.
