Physics

Ever since Austrian physicist Erwin Schrödinger simultaneously killed and did not kill his unfortunate cat, fellow scientists have been using quantum theory to explain and understand the nature of waves and particles. Quantum theory is a branch of theoretical physics that strives to understand and predict the properties and behavior of atoms and particles. One aspect of the theory is that the precise properties of a particle are not determined until you observe them and "collapse the wave function". Schrödinger's famous thought experiment extends this idea to our scale. A cat is trapped in a…

Nowadays whenever I set out to write about CMS I turn on a self-censorship co-processor in the back of my mind, one which is instructed to check that all the sentences I write are completely free from any possible misinterpretation or slant that may cause some colleagues to complain. Oh, strike that, we're a big family and we all love each other. The topic of today is in fact potentially explosive - how experiments perform their blind searches and the potential bias that results from the detailed procedures they employ. However, you will be disappointed by reading this article if you search…

Today the arxiv features the paper describing the final word by the CDF experiment on its searches for the standard model Higgs boson. This paper supersedes previous ones describing searches performed in partial datasets and including only a subset of the decay channels that have been used, so if you are interested in knowing how CDF did in the end, that is the article to read. Or the present one, if you have less time to spend on the matter, or if you are interested in an ex-post evaluation of sensitivity predictions! The CDF article is 29 pages long, but most of the stuff you are probably…

The DZERO collaboration has released last week the result of their search for the rare decay of B_s mesons into muon pairs, based on the full statistics of proton-antiproton collisions acquired during Run II - a total of 10.4 inverse femtobarns of integrated luminosity. The result is not groundbreaking, in the sense that as expected no signal is observed in the DZERO data. [The LHCb collaboration at CERN has obtained a first evidence of this process last November, as discussed in this other article]. The collaboration can only set an upper limit on the branching fraction B(B_s -> μμ),…

A century ago, “past” and “future”, previously strictly apart, mixed up and merged.  Temporal terminology improved.  Today, not actualized quantum states, that is merely “possible” alternatives, objectively “exist” (are real) when they interfere.  Again, two previously strictly immiscible realms mix.  Today, not temporal, but modal terminology (~ how to use the word "possible") is insufficient. The full unification of relativity and quantum mechanics can gain momentum from modal realism, which is basically just the realization of that my present situation is a contingent…

It has been a while since the last time I posted the last riddle of this series. It was fun though, so upon seeing the graph below I immediately decided I would use it here, to let you guess what it is about. Please use the comments thread to provide your input: what does the graph represent ? What are the different coloured lines ? Why the funny behaviour ? What is on the x axis ? And on the y axis ? Of course it is virtually impossible to answer all the above without being given some hint. I can tell you it has to do with LHC searches, and that is all the help I am going to give you!

Ben Kilminster is a friend and a distinguished colleague working for the CMS and CDF experiments. Besides being a long-time higgs hunter, having sought that particle for over a decade in the two mentioned experiments, Ben is a veteran of science outreach since for many years he has published summaries of CDF results for the public on the online magazine "Fermilab Today". When I saw him posting on a social network an earlier version of the text below, which I liked a lot, I asked him to make it a guest post entry for my blog, and he graciously agreed. The piece is titled "How The Universe…

The new PDG - a full-size copy of the glorious "Review of Particle Properties"- is on my desk since its arrival a few weeks ago, but only today did I get some time to browse it. It is always awesome to observe how much information is contained in it. It is 1526 pages long, and I wonder how many typos and mistakes are contained in the data-thick pages... Probably much fewer than an ordinary book. Some of the review articles are of exceptionally good quality, because they have been passed from hand to hand in the last few dozen years, and constantly improved. If you want an example, for…

Gravity is an amazing force. It can grow enormous structures in the universe. If you ever find yourself under a dark night sky at a spot far away from city light, have a look at the constellation Andromeda. With bare eyes you should just be able to spot a tiny smudge in this constellation. You need good eyes that are well adapted to the dark, and the moon with its overwhelming brightness needs to be out of sight. And it definitely helps if you happen to carry with you a pair of binoculars. Once you have spotted it, look more closely at that faint smudge. It is the furthest object you can see…

I may have been unattentive to recent papers on Supersymmetry, but I got the impression that during the last few months the majority of SUSY phenomenologists have been keen on speculating on the few apparently non-standard features of the recently discovered Higgs boson, as published last June (such as the alleged copious decay of photon pairs, or the dearth of decays to tau lepton pairs or b-quark pairs - note: all are mostly back to what the standard model predicts, after the analysis of more data following the discovery announcements), but rather improductive on the front of taking the new…