Physics

No, not a modification of the now classic "Say of the week" series. Rather, a quote from a very famous Physical Review article which is of relevance to a couple of questions I offered here and here this week: In order to insure that the detection efficiency be completely independent of the direction of the positron from the decay of the muon, the observers were instructed to measure only those events that were detected by first seeing the decay. All events so found were used in the analysis except those in which the muon decays occurred within 50 microns of either surface. When a decay…

“Room for one please!” Josef was impatient. He was tired. It had been a long hot day and he needed a bath. “Of course sir. How many nights?” “Twenty-one nights, I will be leaving the same day in three weeks time.” “Your name please?” “Loschmidt. Josef Loschmidt.” Josef listened to the rattling of the keyboard. This young man was quick and seemed experienced. The clerk handed over a key card. “You have room 13 sir, it is indicated in binary on your smartkey card. The number of bits on the card indicates the floor number, tonight you will be on the fourth floor.” Josef looked at his keycard…

Okay, the year is not over just yet, but it is already time for a little accounting of the traffic on this site in the course of the last eight-and-a-half months -that is, since I moved my blog to Scientific Blogging. For this year's summary I have been inspired in part by Alex Antunes, who decided to pick his least read articles to draw some conclusions about what really does not sell well here. But I have of course also given a close look at what appears to appease your taste, dear readers. When discussing the visit statistics of articles which got many hits, one should be careful to bear…

The turnaround of the three physics questions I offered a few days ago, to stimulate your neurons and extract you from the chocolate and alcohol flood caused by the usual string of Christmas parties and dinners, was rather scarce. Despite that, I wish to repeat the offer today, making some adjustments to reach a wider public. The questions I offer here are easier but still not accessible to everybody. However, my plans are that at least the answers I will give in a couple of days will be understandable. Further, anyone can try the bonus question I ask at the bottom of this piece... So below…

Two days ago I offered you three problems in experimental particle physics, of varied complexity. Three readers tried answering the test in the comments thread: a rather underwhelming turnaround, but what did I expect - we are deep in Christmas vacations after all. I will give below my own answers to the questions, and then comment some of those I received. For ease of reading, I paste here again the three questions. 1. The charged pion is a particle made by a  pair of quarks: for the positive one we have the composition , and for its antiparticle . The charged pion decays in about ten…

Scared by the void of Christmas vacations ? Unable to put just a few more feet between your mouth and the candy tray ? Suffocating in the trivialities of the chit-chat with relatives ? I have a solution for you. How about trying to solve a few simple high-energy physics quizzes ? I offer three questions below, and you are welcome to think any or all of them over today and tomorrow. In two days I will give my answer, explain the underlying physics a bit, and comment your own answers, if you have been capable of typing them despite your skyrocketing glycemic index. 1. The charged pion is a…

It is over, but it was frantic. Luca, the Ph.D. student who works with me at the analysis of CMS data (the one which has brought us to the approval of a first signal of the phi meson) summarized it best on Tuesday evening, at the party thrown by our big boss Dario. Holding a glass of good wine in his right hand, and a platter of assorted appetizers in the other, he said: "It is a delirium to work with you: your activity profile is a succession of Dirac deltas". Quite true: usually the share of working time I am capable of devoting to data analysis is reduced to zero by a succession of errands…

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Two days ago, there was a post on backreaction about the naturalness in science, which is considered by many as a fundamental concept. The point of view expressed in the post is quite easy to grasp : naturalness is not a justified argument in any sense (edit : see the comment of the autor below). No need to say that I know a bunch of people who would feel quite offended by these kind of statement. As a response, this post in the reference frame is quite enlightning, and I must admit that although I find him quite rude in his manner, it happens I often agree with Luboš Motl concerning…

This morning LHC machinists, experimentalists from the LHC experiments, as well as other CERN personnel gathered in the Main Auditorium at CERN to give their end-of-year report. After a LHC status report the spokespersons of ALICE, ATLAS, CMS, LHCB, and TOTEM briefly flashed their first experimental results, obtained from 900 GeV and 2.36 TeV collisions acquired in the course of the last three weeks. The amount of results that the collaborations have managed to produce in such a small time frame, and from a relatively small amount of collisions, is really astonishing. Of course most of them…