In case you are interested, I’ve written a short article about Cerenkov radiation, explaining very briefly what it is, why it is so useful in particle physics experiments, and how it can be used to test Einstein’s theory of relativity.
Coming later today or tomorrow: a new set of comments on OPERA and neutrinos that arrive before they were expected.
ON October 6, 2011
Many of you, learning of the OPERA experiment’s claim (whose plausibility is dropping rapidly) of maybe-faster-than-light neutrinos, may have wondered (a) how do physicists know so much about neutrinos, and (b) what was the OPERA experiment originally designed to do? [Hint: Only as a side project did the OPERA experiment set out to measure the speed of the neutrinos, and that’s why its design was by no means ideal for that purpose. ]
I’ve written an article that tries to explain the answer. It describes how there are multiple ways to classify neutrinos that are mutually exclusive, and this leads to a strange, and scientifically crucial, quantum effect called “neutrino oscillations.” After you’ve read the article, I hope you’ll have the language to understand this description of what the OPERA experiment was originally designed to do: Its original goal was to study a particular effect of neutrino oscillations, by sending muon-neutrinos traveling through the earth for 730 kilometers, oscillating as they go, (more…)
ON October 5, 2011
Unbelievable; yet again, for the fourth or fifth time since July, something related to high-energy physics hits the front pages. This time it’s not a shocking claim of a novel phenomenon, but a thoroughly expected Nobel prize awarded for the field’s greatest discovery of the 1990s: that not only is the universe expanding (as Edwin Hubble discovered in 1929), it is expanding more and more rapidly. The teams in which the prize-winners participated used Type Ia supernovas to make the first direct observations indicating that the universe is dominated by something like a “cosmological constant”, often now called “dark energy”. [What these terms really mean deserves a longer article.]
It is interesting, given the historical juxtaposition of this award with the chaos and media circus of ten days ago, to compare this result with the OPERA experiment’s claim that neutrinos arrive earlier than expected. (more…)
ON October 4, 2011
Two weeks ago, a colloquium; last week, a workshop talk; and this week starts with yet another presentation, in the form of a “seminar”. In academic departments, especially the sciences, the term in this context refers to a talk, usually an hour long, about one’s recent research, given to the graduate students, postdoctoral researchers and faculty in one’s sub-discipline. Seminars are pretty common; I’ve given as many as a dozen in a year, and most institutions host one or two every week.
The topics of today’s talk? (more…)
ON October 3, 2011
[If you are a layperson interested in the faster-than-light neutrino claim, and you haven’t yet looked at my recent “open-space’’ post and the list of excellent questions laypeople have asked in the comments, you definitely should. And ask your own if you want. That post also gives an organized list of links to my main posts on the neutrino experiment.]
Today is a sad day in American particle physics. It is the day that Fermilab will shut down the Tevatron, once the world’s leading particle accelerator, which discovered and measured the mass and other properties of the top quark (the sixth discovered, and by far the heaviest), tested the Standard Model of particle physics in very great detail (confirming that everything I wrote in this post about the known particles is correct to the available precision of the experiment), and looked hard for the Higgs particle before being overtaken by the Large Hadron Collider. (more…)
ON September 30, 2011
For me, one of the great pleasures of scientific research is the small, focused “workshop”, where a few scientists (typically 20 — 40 faculty, postdoctoral researches and students) assemble for a day or two to discuss a particular topic in detail. Presentations are typically short and often quite informal, and there’s lots of time for discussion built in to the schedule. The best workshops, of course, are those where the quality of the science and the knowledge, experience and skill of the participants is exceptional. I was fortunate to enjoy such a workshop yesterday at Imperial College in London, one of Britain’s finest scientific institutions. About half the participants were experimentalists from the CMS experiment at the Large Hadron Collider (LHC) and the other half theorists like myself (one of whom is also on the ATLAS experiment at the LHC.)
Another great pleasure in doing science, at least in my field, is its international nature. The participants from yesterday’s workshop included scientists from at least seven countries and three continents, many of whom are now working in a country that is not their native land. Add to this diversity of cultures, appearances and accents some lively personalities, good senses of humor, and high quality science, and you have the ingredients for a very serious workshop that is a very serious form of fun, followed by much less serious fun when the workshop is over and everyone who can stick around goes out to a pub, a restaurant, and then another pub. (more…)
ON September 30, 2011
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