The Large Hadron Collider is increasing gradually the number of proton bunches that circulate in the machine. Yesterday's fill saw 104 colliding proton bunches, producing the record instantaneous luminosity of 3.5 x 10^31 collisions per square centimeter per second. This is no surprise, of course: luminosity is essentially the product of the number of particles crossing each other per second divided by the cross section of the beams, so if you increase the particles and manage to keep the beam transverse size constant, luminosity must go up.
"At that time, although recognized for the very high quality and reliability of its accelerator engineering, CERN unfortunately did not have a similar reputation in its physics, and it was still recovering from disasters such as the "split A2" affair. CERN always seemed to be second best behind the leading U.S. laboratories, with their vastly more experienced physicists. And during the 1960s it had been repeatedly beaten into the ground, for example, over the discoveries of the Omega- hypheron, the two types of neutrinos, and CP violation in K0 decay. All these things could and should have been found first at CERN, with its far greater technical resources, but the Americans had vastly more experience and know-how."
Donald Perkins
Despite time is a scarce resource for me these days, and my "working time balance" shows deep red, I am presently spending some of it to investigate a very interesting statistical effect of general nature, although specially connected to the issue of discovery thresholds in particle physics.
I am triggered by the recent eported observation of a new particle, which has been claimed at a significance corresponding to the coveted 5 standard deviations after a previous evidence had been extracted from 40% less data at 3.8 standard deviations. The matter has left me slightly dubious about the precision of the latter claim.
Now, before I state the problem, let me explain in short how significance is calculated in these kinds of new particle searches.
I devote only a short piece today to the topic of the week -or the month- in particle physics: as many of you already know, yesterday
the CMS collaboration has made public the results of their analysis of two-particle correlations, which evidences an effect never seen before in hadronic collisions, and which has been saluted very emphatically by the press around the world.
The Analysis In Ten Lines
I am currently running an experiment, with multiple aims. I have created
a new blog in wordpress, where I intend to publish a translation to modern Greek of selected articles that I have written in the past. The first attempt is already there (work is in progress, though, given my multiple occupations these days). In the blog I also offer to translate older posts on demand.
"If they would only do as he did and publish posthumously, we should all be saved a lot of trouble".
[Maurice Kendall, famous British statistician, talking of Bayesians (statisticians who employ Bayes' theorem and Bayes' approach to statistical inference, particularly related to the use of "prior beliefs") and of Bayes himself, whose groundbreaking work was only published after his death]
A Chess Study Requiring Backpropagation
Co-Design Of Scientific Experiments
Travel With Two Infants
A Nice Little Combination
