Experiment
drorzel | September 28, 2006This is the third in a series of posts covering the basics of particle physics, originally posted back in 2003. In this installment, I talk about some of the hardware involved, specifically the CLAS detector at Jefferson Lab, because I've heard a good number of talks about that.
It should be noted that the inspiration for this whole thing was the announcement of the discovery of a "pentaquark" particle at a couple of accelerators. That discovery is by no means certain, but I'm still fairly happy with the explanatory aspects of these posts. I'm certainly not bothered enough to re-write them.…
drorzel | September 27, 2006This is the second of a set of old posts, dating back to 2003, discussing the business of experimental particle physics. In this installment, I talk about how you get exotic particles by slamming ordinary ones together at high speed.
In a previous post, I gave a quick outline of the Standard Model of elementary particles, and how it relates to the recent discovery of a new particle. The best illustration of the process is probably the picture on the Ohio University reference page: A deuterium nucleus (one proton and one neutron) is sitting there, minding its own business, when a photon comes…
drorzel | September 27, 2006Since I found myself talking about particle physics yesterday, and since I find myself in the middle of a seasonal allergy flare-up that's sapping my bloggy motivation, I thought I would dust off and re-post some old articles about particle physics. These date back to 2003, but I think they still stand up reasonably well.
This is the first of four Classic Edition articles, covering the different types of particles making up matter in the universe.
A few days ago, I linked to a news story about this paper in Physical Review Letters describing the discovery of a new type of subatomic particle.…
drorzel | September 26, 2006I end up buying a lot of weird things for my lab-- really expensive sand, for example-- but the latest purchase was a little strange even by my usual standards:
The other day, on my way into work, I stopped by the store and bought a roll of parchment paper, for use in the lab. It actually makes perfect sense, though it'll require a little explanation, below the fold
The brass thing in the picture above is a length of 3" diameter pipe, which is intended for use as a holder for a magnetic field coil. The coil, one of a pair used to produce a magnetic trap for neutral atoms, will consist of…
drorzel | September 26, 2006Quantum Diaries survivor Tommaso Dorigo offers an inside look at experimental particle physics, describing new results from combing through CDF data to look for rare events producing two leptons with the same charge:
Indeed, 44 events were found when 33.7 were expected, plus or minus 3.5. That corresponds to a roughly 2-sigma fluctuation of expected counts. The picture on the left shows the leading lepton spectrum for the 44 events in the signal region.
What he leaves out is that this is 44 events out of a total number that's almost certainly in the millions. Particle physicists are sort of…
drorzel | September 26, 2006Dave Bacon explains heating-induced decoherence:
One problem with ion traps qubits has been the heating of the motional degrees of the trapped ions, due mostly to fluctuating potentials on the trap electrodes. The electrode potential goes yee-yaw and the ion goes wee-wah, heating up and thus ruining the motional degree of freedom of the ion.
See, this is why he gets to be Pontiff, and I'm a cardinal at best...
The highly technical use of "yee-yaw" and "wee-wah" is in order to introduce a new paper from Chris Monroe's group in Michigan, who have found that cooling the trap electrodes greatly…
drorzel | September 7, 2006This is nearly a month old, now, because I keep saying "Oh, Idon't have time to do this justice-- I'll write about it tomorrow." I really need to stop doing that.
Anyway, Physics News Update has a story about a scheme to measure gravity using Bloch oscillations, based on a paper in Physical Review Letters. This is especially interesting to me, because the most important paper of my career made use of Bloch oscillations to get our experimental signal.
A quick explanation below the fold:
Bloch oscillations are a weird phenomenon you encounter in condensed matter physics. The easiest way to…
drorzel | August 15, 2006I'm in the process of putting together my tenure documents (I know I've been saying this for weeks. It's a long process, OK?). Most of these are really not appropriate for reproduction here, but I'll post a few of the things I'm writing, when it's reasonable to do so.
A major part of the tenure process is finding external reviewers for the research material. As most institutions don't really have enough people in a given sub-field to assess research in-house (especially at a small college), and as trusting such an assessment would be a little dodgy, the research review is traditionally…
drorzel | July 12, 2006An off-hand comment in my RHIC post has provided a lot more traffic and entertainment than I would've thought possible, and has also accidentally re-confirmed what we used to call "Furr's Law" back in my Usenet days-- namely, that the fastest way to get information on the Internet is to say something wrong, and let people rush to correct you. (Please note, I'm not saying I deliberately slighted string theory in order to discover RHIC resources-- I deliberately slighted string theory for the sake of a (not terribly effective) joke.)
Anyway, the responses have provided a wealth of String Theory…
drorzel | July 7, 2006I had errands to run this morning before work, which meant that I didn't have time to queue up the usual handful of blog posts to appear during the day. I don't want to have the site go dark, though, so I'll throw up a post or two on my lunch hour, to note some physics stuff that's kind of cool.
I've been meaning to say something about this for a while, as the physics blogosphere has been overrun with talk about how cool the Large Hadron Collider is going to be (my own contribution is a few posts back), but I keep putting it off on the theory that I'll do something really substantial. The…
drorzel | July 6, 2006The last couple of days at work have been Shop Days, with a fair bit of time spent in the department's machine shop making holes in a metal box. This would, I'm sure, be the occasion of much hilarity among my old junior high shop teachers, as my ineptitude in both metal and wood shop was pretty impressive, back in the seventh and eighth grades. I've gotten considerably more coordinated since those exceptionally gawky days, though, and I can use a drill press or a mill without too much trouble now, though no-one will ever mistake me for a machinist.
In a certain sense, Shop Days are among the…
drorzel | July 6, 2006My Corporate Masters have finally posted the piece that ran in the most recent print edition of the magazine, in which prominent physicists comment on the LHC. They've got predictions and explanations of why the LHC is interesting from an impressive array of people.
Most of the answers are pretty predictable. Lisa Randall talks about extra dimensions, Leonard Susskind about the Anthropic Principle, etc. My favorite answer, though, is Steven Weinberg's:
What terrifies theorists is that the LHC may discover nothing beyond the single neutral "Higgs" particle that is required by the standard…
drorzel | June 29, 2006I ended the previous laser post by noting that diode lasers need some additional wavelength selection to be done in order to be useful as light sources for spectroscopy experiments. In their natural state, they tend to emit light over a broader range of wavelengths than is really ideal, and we'd like to narrow that down, and also to be able to control the emission.
(I should note that, while the emission of a typical diode laser is broader than people doing atomic physics experiments would like, it's still incredibly narrow by normal standards. The actual width, in wavelength, of the light…
drorzel | June 29, 2006A little while back, JoAnne at Cosmic Variance reported on the status of the Large Hadron Collider (LHC), the giant next-generation accelerator that is the cover story for the current print issue of Seed. Particle experimentalist Gordon Watts reports in with some more technical details about the delay in the proposed turn-on schedule. He's also got a link to a PDF of a talk by someone associated with LHC, for those who really want to geek out.
The bottom line appears to be that this is just normal, prudent caution, and not really unexpected. Though the delay is a little disappointing to those…
drorzel | June 16, 2006Rob Knop has another post to which I can only say "Amen!", this time on the relatioship between simulation and experiment (in response to this BoingBoing post about a Sandia press release):
Can simulations show us things that experiments cannot? Absolutely! In fact, if they didn't, we wouldn't bother doing simulations. This has been true for a long time. With experiments, we are limited to the resolution and capabilities of our detectors. In astronomy, for example, we don't have the hundreds of millions of years necessary to watch the collision of a pair of galaxies unfold. All we can look at…
drorzel | April 27, 2006The big physics story of the day is bound to be this new report on American particle physics:
The United States should be prepared to spend up to half a billion dollars in the next five years to ensure that a giant particle accelerator now being designed by a worldwide consortium of scientists can be built on American soil, the panel said. If that does not happen, particle physics, the quest for the fundamental forces and constituents of nature, will wither in this country, it said.
You might assume that, as a physicist, I'm all in favor of this-- half a billion is a lot of money, after all…
drorzel | April 21, 2006I'm still feeling pretty lethargic, but I hope that will improve when I get to lecture about the EPR paradox in Quantum Optics today (it's going to be kind of a short lecture, unless I can ad-lib an introduction to Bell's Theorem at the end of the class, but then I've been holding them late for three weeks already...). In an effort to perk myself up through blogging, here are some amusing tales about mishaps involving electricity.
(First, a disclaimer: Though these stories are presented in a manner that (hopefully) makes them sound amusing, most of what I describe here is, in fact, incredibly…
drorzel | April 11, 2006One of the features I always like in the print edition of Seed is the lab notebook pictorial. Every month (or, at least, all three of the months that I've looked at the print edition), they publish a reproduction of a page or two from the lab notebook of a working scientist. It's sort of cool to see how they differ from one field to another, while remaining largely the same.
Back when I was doing the "A Week in the Lab" series of posts, somebody asked me about my own lab notebooks. I present here the reason why Seed is never likely to ask me to supply notebook pages for their monthly feature…
drorzel | March 24, 2006A reader emails to ask if I can make sense of this announcement from the European Space Agency:
Scientists funded by the European Space Agency have measured the gravitational equivalent of a magnetic field for the first time in a laboratory. Under certain special conditions the effect is much larger than expected from general relativity and could help physicists to make a significant step towards the long-sought-after quantum theory of gravity.
Just as a moving electrical charge creates a magnetic field, so a moving mass generates a gravitomagnetic field. According to Einstein's Theory of…
drorzel | February 24, 2006The votes are in, and have been carefully tabulated by our bleary-eyed accounting firm (that is, me-- I would've posted last night, but I went to see Chuck D speak (because I'm down with the old-school rap), and he went on for more than two hours...) . What looked like a runaway victory for Michelson and Morley actually tightened up quite a bit, thanks to a late surge by Michael Faraday:
Michelson-Morley: 23
Faraday: 19
Rutherford: 10
Galileo: 9
Roemer: 9
Aspect: 8.5
Hertz: 3
Cavendish: 2.5
Newton: 2
Hubble: 2
Mössbauer: 1
A total of 89 people voted, 90 if you count the one write-in vote…