Andrew Jaffe: Leaves on the Line

PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) is a Russian-Italian satellite measuring the composition of cosmic rays. One of the motivations for the measurements is the indirect detection of dark matter — the very-weakly-interacting particles that make up about 25% of the matter in the Universe (with, as I’m sure you all know by now) normal matter about 5% and the so-called Dark Energy the remaining 70%. By observing the decay products of the dark matter — with more decay occurring in the densest locations — we can probe the properties of the dark particles. So far, these decays haven’t yet been unequivocally observed. Recently, however, members of the PAMELA collaboration have been out giving talks, carefully labelled “preliminary”, showing the kind of excess cosmic ray flux that dark matter might be expected to produce.

But preliminary data is just that, and there’s a (usually) unwritten rule that the audience certainly shouldn’t rely on the numerical details in talks like these. Cirelli & Strumia have written a paper based on those numbers, “Minimal Dark Matter predictions and the PAMELA positron excess” (arXiv:0808.3867), arguing that the data fits their pet dark-matter model, so-called minimal dark matter (MDM). MDM adds just a single type of particle to those we know about, compared to the generally-favored supersymmetric (SUSY) dark matter model which doubles the number of particle types in the Universe (but has other motivations as well). What do the authors base their results on? As they say in a footnote, “the preliminary data points for positron and antiproton fluxes plotted in our figures have been extracted from a photo of the slides taken during the talk, and can thereby slightly differ from the data that the PAMELA collaboration will officially publish” (originally pointed out to me in the physics arXiv blog).

This makes me very uncomfortable. It would be one thing to write a paper saying that recent presentations from the PAMELA team have hinted at an excess — that’s public knowledge. But a photograph of the slides sounds more like amateur spycraft than legitimate scientific data-sharing.

Indeed, it’s to avoid such inadvertent data-sharing (which has happened in the CMB community in the past) that the Planck Satellite team has come up with its rather draconian communication policy (which is itself located in a password-protected site): essentially, the first rule of Planck is you do not talk about Planck. The second rule of Planck is you do not talk about Planck. And you don’t leave paper in the printer, or plots on your screen. Not always easy in our hot-house academic environments.

Update: Bergstrom, Bringmann, & Edsjo, “New Positron Spectral Features from Supersymmetric Dark Matter - a Way to Explain the PAMELA Data?” (arXiv: 0808.3725) also refers to the unpublished data, but presents a blue swathe in a plot rather than individual points. This seems a slightly more legitimate way to discuss unpublished data. Or am I just quibbling?

Update 2: One of the authors of the MDM paper comments below. He makes one very important point, which I didn’t know about: “Before doing anything with those points we asked the spokeperson of the collaboration at the Conference, who agreed and said that there was no problem”. Essentially, I think that absolves them of any “wrongdoing” — if the owners of the data don’t have a problem with it, then we shouldn’t, either (although absent that I think the situation would still be dicey, despite the arguments below and elsewhere). And so now we should get onto the really interesting question: is this evidence for dark matter, and, if so, for this particular model. (An opportunity for Bayesian model comparison!?)

Welcome to anyone one led here from Physics World’s Blog life column. This is a blog — so comments are encouraged (or you could click on the advertisements)!

It’s making the science-blogging rounds today that Obama has answered the questions posed as Science Debate 2008, questions on education, health care, stem cells and, of course, climate. He supports all the right scientific positions, and says several times that he will increase funding for basic research overall, but most importantly acknowledges and condemns the ideological and political interference that has plagued US research during the Bush administration.

McCain will, apparently, follow with his answers soon.

Meanwhile, here in the UK, the lengthily-named Department for Innovation, University and Skills (DIUS) is holding a consultation on Science and Society where you can answer questions like “How should scientists be rewarded for their efforts to communicate science to the public?” (I’m thinking big wads of cash.)

NASA’s latest space-based telescope has, until now, been known as the Gamma-Ray Large Area Space Telescope (GLAST). Today, they announced the very first results, and renamed it the Fermi Space Telescope, after physicist Enrico Fermi. Fermi was one of the pioneers of modern particle physics, part of the Manhattan Project generation that created the fundamental theories and techniques that we still use today, although he died sadly young before he could see the fruition of his work in today’s standard model of particle physics. He also thought hard about a number of more speculative issues, including wondering why, if life is common in the Universe, we haven’t met any other sentient creatures yet (a question known in fact as the Fermi Paradox) — and worried that the answer might be that civilizations tend to blow themselves up.

Today’s results came in the form of an all-sky map. The band in the center is gamma-ray emission from the Milky Way galaxy, and three of the four bright spots are pulsars — fast-spinning, magnetized neutron stars, and the fourth is a kind of distant active galaxy known as a “Blazar”.

I wonder how long before someone will compare the GLAST (Fermi) maps with the microwave-band maps from WMAP like this one:

The way gamma rays are created is very different from the emission microwaves, but any soup of gas, dust, stars and magnetic fields is likely to produce both.

Just as exciting as these maps is GLAST’s ability to find Gamma-Ray Bursts, some of the most energetic objects in the Universe, whose mechanisms are still poorly understood, and which may let us peer to the epoch of the formation of the very first objects.

(All images courtesy NASA.)

For some reason a lot of music books have percolated to the top of my bedstand pile recently. I just finished Alex Ross’ magisterial and definitive The Rest is Noise, a history of 20th Century “Western Classical” music. (Let’s pause for a moment and praise the genius of that title, by the way.) The book starts with Strauss, Mahler and Debussy and ends with John Adams and some of my recent obsessions: Arvo Pärt, Steve Reich and Olivier Messiaen, whose Quartet for the End of the Time is at the Proms next week. (For me, really a neophyte with this kind of music, the book was an ideal companion to Paul Morley’s Words and Music, which turned me onto this music by reimagining the history of rock’n’roll as if driven not by the blues but by the resolutely white-boy classical tradition: it starts and ends with Alvin Lucier’s minimalist “I am Sitting in a Room” and Kylie’s “Can’t Get You Out of My Head”.)

But the centerpiece of Ross’s book is three chapters on the way politics drove the musical agenda (or at least tried to) in mid-century Germany, America and the Soviet Union. The unspoken but eventually obvious point comes through, that the music can’t help be of its place and time, a product of the world around it, but that our duty is just to listen, not forgetting the history, but not paying it too much attention, either.

I’ve also been reading Love is a Mix Tape, Rob Sheffield’s music-tinged memoir, concentrating on the loss of his first wife, Renée, far too young. I’m lucky enough to have known Rob for more than 20 years, and that made the book both hard to put down and, when the going got tough, recalling for me the day when Rob phoned to tell me the terrible news about Renée, hard to pick up. But it’s a lovely, moving, book, managing to set down the emotional pull of music’s private meaning and the way it connects to the people listening with us, even on an iPod hundreds or thousands of miles away. (You can hear Rob reading some excerpts at the book’s site.; there’s a wonderful NPR interview with Rob, too.)

Now, I’m on to Simon Armitage’s Gig, also a memoir, this time by a music-obsessed British poet.

(By the way, does anyone have a definitive attribution for “Writing about music is like dancing about architecture”? I’ve mostly heard Elvis Costello, but also Steve Martin.)

There’s a new Google-competing search engine called Cuil (which I guess is meant to be pronounced as slacker-speak “kewl” or something). If I search for myself on it, my Imperial homepage comes up first, but for some reason accompanied by this picture. I promise that’s not me. Just as strange, a picture that is of me comes up next to a blurb for a book written by another Andrew Jaffe who happens to be the director of the Clio Awards for advertising (there are a few of us Andrew Jaffes out there, but I’m egotistically happy to tell you that I’m top in most search engines). But I’m happiest about the cover shot from Muscle Magazine (not me either).

I’ve had this Fermilab-labeled mug ever since I spent the summer working there in 1990 (the picture is from a few years later — ignore the sartorial mis-step of the slouch-shouldered cardigan). Today, sadly, I dropped it fumbling with the keys to my office.

Actually, that was a pretty fun summer. I was working on an idea to detect cosmic axions, with a setup similar to some ongoing experiments but using somewhat odd ferrimagnetic materials. Axions are one of the possibilities for the omnipresent but difficult-to-detect dark matter. For the first and only time in my life, I got to play with superconducting detectors, RF cavities and old-fashioned strip-chart recorders, and not just for some assigned lab project. Alas, the idea didn’t pan out, and axions still haven’t been detected (despite a couple of claims to the contrary).

OK, not a vacation in the true sense of the word: I’ve been in the US, attending meetings (in Berkeley), workshops (in Santa Fe), conferences (in Pasadena) and, because I can’t seem to escape them, teleconferences everywhere and all the time.

Berkeley

In Berkeley, I attended the first all-hands collaboration meeting for PolarBear, an experiment that will measure the polarization of the CMB from a telescope that will eventually be situated on the Atacama desert plain in Chile — one of the highest, driest, least accessible places on the earth, and one of the least contaminated with light or radio interference. (Despite the name of the experiment, there are no polar bears there.) First, we’ll test it at the somewhat less remote White Mountain facility in California, shake out all the bugs. PolarBear is one of a new generation of experiments that will measure the CMB using not just a few tens of detectors, but a few thousand, which brings with it all sorts of technical challenges. In hardware, the first challenge is simply making so many detectors and keeping their properties uniform each to each — these are among the most sensitive microwave detectors ever built, essentially as good as the constraints of quantum mechanics and thermodynamics allow. The second, related to the first, is to pack as many of these into a small space — the focal plane of the telescope — as possible. Traditionally, microwave detectors have used horns to guide the electromagnetic waves from the sky onto the detectors, but those horns are much wider than the detector hardware. For experiments like PolarBear, we put the detectors themselves right at the focus of the telescope and make each of them into a little antenna, receiving directly the focused light after passing through a hemispherical lens. The final hardware challenge is to get the information from these thousands of detectors off of the telescope and into our computers, which the PolarBear designers have solved with a new technique called “frequency-domain multiplexing”. Sort of like the way FM radio manages to convey the full spectrum of sound by modulating at a particular frequency, the very high-tech SQUIDs (Superconducting QUantum Interference Devices) can then amplify these tiny CMB signals into data we can analyze.

In fact, the data analysis and computing challenges are almost as significant as those faced in hardware. With thousands of detectors and a telescope that will run for the better part of several, we have many orders of magnitude more CMB data than we’ve ever dealt with before, combined with a sensitivity goal better than a millionth of a degree. By adding more and more detectors, we can make the raw experiment itself sensitive enough to do this. What we don’t know is whether we can eliminate everything else that can possibly contaminate our results: light may spill over our shield from the 300 degree ground or directly from the atmosphere; dust in our solar system or our galaxy also glows in the bands we want to measure, as do external galaxies millions of light-years away. So our task is to compress the terabytes of data into a few interesting numbers (like the energy scale of inflation) and to simultaneously separate the cosmic signal from the that produced by instrument and from the rest of the Universe (which may be much brighter!). Suffice to say, we have some good ideas but until we’re confronted with real data we won’t know how successful we’ll be.

Plus, I ate bagels (better than London; not as good as New York) and burritos, and bought shoes at cheap American prices (at least when I think in British Pounds).

Next up, Santa Fe…

Thanks to Dave for pointing out that the final results of the STFC programmatic review sweepstakes popularity contest consultation exercise have been released. Following on from the recommendations, which grouped all projects into five projects, the STFC Council has decided where and how the money will flow.

The best news overall is that only the very lowest band of projects will no longer be funded, rather than two lowest as had originally been planned. As expected, Imperial Astrophysics has fared relatively well, with continued support for Planck, Herschel, Scuba II, UKIDSS, LISA Pathfinder and XMM Newton.

Overall, it looks like a relatively small number of projects will be “discontinued” and that STFC “will therefore ramp down funding at an expeditious but appropriate rate in consultation with the PIs/stakeholders. Where possible [they] will look for ways to ensure that there is a return on … previous investments.” In astrophysics, these projects include the UK’s contributions to the gamma-ray observatory VERITAS and the astronomical computing and data-analysis projects AstroGrid and CASU/WFAU, in particle physics the b-physics experiment BaBar, and most of ground-based Solar and Terrestrial physics. On the other hand, despite the panel recommendations which put it into the lowest band, the Mercury mission BepiColombo — which apparently threatens to consume the entire ESA science budget — will continue to be funded, because the UK contribution “is subject to an MOU [memorandum of understanding] with the Agency and will be respected.”

But the dark underside to the entire process remains the assumed 25% cut to the “grants line” — the money to pay for the actual science return on these missions, as well as all of the science that doesn’t come from large projects, mostly in the form of salaries for postdocs: theoretical physics, observations of individual astronomical objects, and just thinking hard and opening up new areas to explore. I’ve just got a big stack of grant applications to referee from STFC — let’s see how many of even the best manage to survive the cut.

[I promise to find something new to talk about, now that this unsavory episode seems to be reaching its conclusion, for now at least. Until then, you’ll just have to follow my twittering, although you’re more likely to learn about my musical tastes than cosmology…]

No time for a full blog post, but I wanted to point out the results of the STFC Consultation, now available.

Some of my favorite projects like AstroGrid seem to have not fared too well (the consultation panel rated it highly, but PPAN, responsible for the final ranks, disagreed). Nonetheless, Imperial Astrophysics projects like Planck, Herschel, Scuba II, UKIDSS, LISA Pathfinder and XMM Newton appear to have survived the cut. However,

It is important to stress that these reports are not the final conclusions of the Programmatic Review. These conclusions will be reached by STFC Council using these reports to inform their decision-making.