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August 2008 Archives

By Jon Cartwright

The debate as to whether the DAMA/LIBRA team has detected dark matter, as it claimed in April, will no doubt persist until fresh data can say either way. But in the meantime, Robert Foot, a physicist from the University of Melbourne, suggests an alternative interpretation: “mirror matter”.

I’ll take a step back for a moment in case you aren’t familiar with the story. (Alternatively, you can see Physics World’s feature.) DAMA/LIBRA is an underground experiment based at the Gran Sasso laboratory in Italy. It looks for dark-matter particles known as WIMPs (weakly interacting massive particles) — a class favoured by theorists for the mysterious substance — by monitoring for flashes that occur when the particles collide with nuclei in 250 kg of sodium-iodide detectors. The idea is that the frequency of flashes should modulate over the year as the Earth changes its speed through our galaxy’s “halo” of dark matter: in June, when the Earth’s orbit takes us faster through the halo, one would expect to see more flashes; in December, when we are moving slower, one would expect to see fewer.

(Credit: Olaf Behrendt)

By Jon Cartwright

Could it be — touch wood — that the Large Hadron Collider (LHC) will make it to the official 10 September start-up date without any further hiccups?

On Friday scientists at the European laboratory CERN were able to tick off two more items on the accelerator’s commissioning list. First, they managed to feed a bunch of protons from the transfer line of the Super Proton Synchrotron (SPS) into the LHC and then steer it some three kilometres round the beam pipe in a counter-clockwise direction. Second, a detector at LHCb — one of the four main experiments at the LHC — got the first taste of collision debris.

(Credit: Chris Lavers)
(Credit: Chris Lavers)

By Jon Cartwright

At first glance these images look like snapshots from that classic eighties sci-fi flick Predator.

It turns out, though, that the pre-eminent being responsible for them is not a brawny, gun-toting alien, but Chris Lavers, a technology lecturer at Britannia Royal Navy College in Dartmouth, UK. The images are infrared portraits of various animals dwelling at Paignton Zoo in Devon.

“I have been involved in thermal imagery for about 10 years now, and thermal imagery of wildlife with Paignton Zoo since 2002,” writes Lavers in an email. “My interest is concerned with highlighting the plight of endangered species under pressure from both man and climate change, deteriorating environments, etc.”

Lavers explains that thermal images can be used to observe animals without stressing them. “It enables a healthy baseline assessment of animals to be established and thereby aids veterinarian diagnosis,” he writes.

Aside from giving giraffes, tortoises and other creatures a once-over, Lavers is also interested in using thermal imaging to copy some of nature’s designs, such as iridescent butterfly wings. These could be employed in future stealth devices, he says.

If you want to see more of Lavers’s images — and are out and about in the south-west of the UK — you can visit his exhibition. It starts on 15 September at Paignton Zoo, and moves onto the Living Coasts zoo in Torquay until the third week of October.

By Hamish Johnston

When it comes to designing detectors for neutrinos, the bigger the better.

At the South Pole, for example, physicists have begun work on the IceCube experiment, which will pepper a cubic kilometre of ice with over 4000 photomultiplier tubes with the aim of detecting tiny bursts of light created when neutrinos interact with the ice.

However, this experiment is tiny by comparison to the NuMoon experiment, which is trying to use the Moon to detect ultra-high energy neutrinos from the far reaches of the universe.

The NuMoon collaboration has just published an analysis of the first 10 hours of observation on the arXiv preprint server.

NuMoon uses the Westerbork Synthesis Radio Telescope in the Netherlands to look for short radio pulses that are believed to occur when an ultra-high energy neutrino creates a cascade of charged particles within the layer of rocks and sand that covers the Moon.

These particles move through this rubble at speeds faster than the local speed of light, creating pulses of Cherenkov radiation that can be detected on Earth using a radio telescope.

The NuMoon team reckon that 100 hours of data will allow them to set the best limit yet on the “GZK neutrino flux” — the number of neutrinos with energies in excess of 1020 eV that pass through the Moon.

Such neutrinos are believed to be produced when ultra-high energy cosmic rays from distant sources scatter from the cosmic microwave background. While this scattering prevents the cosmic rays themselves from reaching Earth, much could be learned about their origins (such as massive black holes) by studying GZK neutrinos.

This is not the first time that astronomers have tried to use the moon as a giant neutrino detector. The idea was first proposed about 20 years ago and there have since been two other experimental attempts — including the GLUE experiment, which failed to spot any ultra-high energy neutrinos.

And if NuMoon fails to detect any neutrinos, the team plan to use successively more powerful radio telescopes such as the Lofar array currently under construction in the Netherlands and ultimately the Square Kilometer Array that should be built by 2020 in either South Africa or Australia.

By Jon Cartwright

Has a European satellite detected dark matter? That’s the question on many people’s lips who attended the recent International Conference on High-Energy Physics (ICHEP) in Philadelphia, US.

Several physicists who attended the conference have told me that Mirko Boezio, a representative of the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) mission, briefly showed data depicting an excess of high-energy positrons in the ionosphere. If true, it would seem to be evidence of annihilation dark matter — an elusive substance thought to make up some five-sixths of all matter in the universe.

Unfortunately, neither Mirko Boezio nor the principal investigator of PAMELA, Piergiorgio Picozza, wants to comment on their data. They told me this was because they are planning to publish in either Nature or Science, and are therefore prohibited from talking to journalists because of those journals’ embargo policies. (Another little birdie told me that the PAMELA team is specifically aiming to submit to Nature by September, so if they fast-track it we might get to see the paper before Christmas.)

I’m going to tell you all I know about this, because frankly it’s not that much at the moment. The slides available from the ICHEP website only show positron data up to about 6 GeV, which doesn’t show much. Slightly better is this slide below from another PAMELA team member, Elena Vannucinni, who gave a presentation at the recent SLAC Summer Institute.

By Matin Durrani

It’s time for me to bow out of the LT25 low-temperature conference here in Amsterdam, which has just ended. The cool crowd will reconvene in three years’ time for LT26, which, I can reveal, will take place in Beijing, at a venue next to the current Olympic park. It’ll be the first time that China will host this triennial shindig.

Conference organiser Peter Kes from the University of Leiden gave some amusing insights into organising a conference of this scale, which saw a staggering 1482 participants. For example, stuffing the massive 380-page (double-sided) conference brochure into delegates’ shoulder bags required a small army of students, who hit a peak rate of 450 bags stuffed per hour.

Then there were the logistics of bussing 640 delegates on a trip to the University of Leiden to see the lab where Heike Kamerlingh Onnes won the race against Scottish physicist James Dewar to liquefy helium 100 years ago last month. Plus sorting out the conference dinner for nearing 600 people, which included hiring a flotilla of nine boats for the trip from the conference halls into town.

Levitating a magnet using liquid nitrogen. (Credit: Yorick van Boheemen)

By Matin Durrani

Tucked away in the corner of the foyer at the RAI Convention Center in Amsterdam, where the 25th International Conference on Low-Temperature Physics has been taking place for the past week, I found a series of great little demonstrations by a group of students from the University of Leiden.

The students were showing highlights from a roadshow — dubbed “Freezing physics” — that they perform at about 120 schools and numerous science fairs around the Netherlands each year in an attempt to get people hooked on physics.

You won’t be surprised to find the usual “ooo, watch how this rubber band/tennis ball/banana goes really stiff when we dunk it into a bucket of liquid nitrogen” demonstrations, which are a staple of many public shows of this kind.

But the students, known collectively as the Rino Foundation, had some clever stuff up their sleeves too. One involved using the frozen banana to hammer a nail into a piece of wood. Another saw a hand-bell being cooled in liquid nitrogen and then rung after being frozen. As the material had stiffened considerably, the bell’s ring tone was much higher than when warm.

By Matin Durrani

This is my second full day at the 25th International Conference on Low-Temperature Physics in Amsterdam — LT25 in the jargon — and it’s been a busy morning, despite last night’s marathon conference dinner at the five-star Hotel Krasnapolsky that lasted until gone 11 p.m.

Almost 600 delegates, myself included, were treated to a fairly decent three-course dinner that culminated in what was billed as a “grand dessert buffet”, which seemed to take forever to set up. Thankfully the wait for the profiteroles, fruit slices and cheesecake was ameliorated by a performance by a Dutch philosophy-graduate-turned-magician, whose name escapes me but who did some clever things with various delegates’ wedding rings.

We were also serenaded by a roving accordion player and guitarist who went from table to table and who claimed they could sing songs in 24 different languages. Which was great, I suppose, as long as you didn’t mind the fact they were all sung with a painfully thick Dutch accent. A Malaysian guy on my table, for example, seemed pretty unconvinced by the pair’s children’s song about a parrot.

But back to the physics. This morning I sat in on a session on “supersolids” — a strange new form of matter that some physicists think exists when helium-4 is cooled down to sufficiently low temperatures and subject to high enough pressure. The jury is still out on whether this form of matter exists, although the consensus, as far as I could tell from today, would be that it does.

Let’s romp

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Laura Greene (left) and Setsuko Tajima (right) with the bust of Heike Kamerlingh Onnes, who liquefied helium 100 years ago last month. (Credit: Dirk van der Marel)

By Matin Durrani

With term over and no students to teach, the summer has always been peak season for scientific conferences. There’s no shortage of interesting meetings to pick from, but I am representing Physics World at the 25th International Conference on Low-Temperature Physics in Amsterdam.

One reason for attending is that the Dutch capital is a short flight from Physics World’s base in Bristol in the UK — so I am either saving money or minimizing my carbon footprint, depending on how you look at things.

Another reason is that IOP Publishing, which publishes Physics World, has had a big presence at the meeting as the proceedings are to appear in our very own Journal of Physics Conference Series.

More importantly, though, there’s just loads going on at this three-yearly bash — from fundamental studies into liquid helium to a host of talks on ultracold atom optics. But one of the highlights so far has been a special “romp” session last Friday on a new class of iron-based superconductors, known rather cumbersomely as the “oxy-pnictides”.

The Green Man festival. (Credit: Stinco di Porco)

By James Dacey

If you read my colleague Michael Banks’s blog entry on Tuesday, you will have heard that Queen guitarist — cum doctor of astrophysics — Brian May is poised to unleash his PhD on popular bookstores from September.

Being a geophysicist — cum amateur guitarist — I am in no position to critique the quality of his astrophysics (nor his ear for a guitar riff!). But I am intrigued by May’s activities.

It remains to be seen whether “A Survey of Radial Velocities in the Zodiacal Dust Cloud” will fly off the shelves. Even less guaranteed is the number that will be bought, read AND understood by non physicists. But leaving aside these concerns for May and his publishers, the point is that a rock star status can provide a platform to encourage non-physicists to take an interest in the subject.

Another public engagement project with a musical stage is “Physics in the Field” and it plays its next gig at the Green Man festival next weekend (14–17 August).

Let me explain.

During the widely-celebrated International Year of Physics in 2005, the Institute of Physics (IOP) sent a small group of volunteers to brave the Somerset mud and host a workshop called “Einstein at Glastonbury”. The idea was to try and spark public interest in physics by dragging demonstrations from the laboratories and plonking them in the more informal setting of a music festival. Being something of an Einstein tribute act, demonstrations linked the physicist’s ideas to music including the inner workings of Rolf Harris’s didgeridoo.

Read all about it

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(Credit: Amazon)

By Michael Banks

When I was a PhD student, I remember having to go through a few rounds of thesis revision, which was usually greeted with a painful moan of once again ploughing through 200 plus pages of dry, technical language, with a few equations thrown in as well. But I never thought about anyone other than a physicist really wanting to read it — even my mum only got as far as the abstract.

Well for all those Queen fans out there, guitarist and astronomer Brian May, who has recently completed his PhD in astronomy at Imperial College London, has now had his PhD thesis published as a book by Springer and Canopus Publishing Ltd.

May’s thesis, and the book too for that matter, is snappily entitled “A survey of radial velocities in the zodiacal dust cloud” and covers the Zodiacal light — a faint diffuse cone of light seen in the west after sunset and the east before sunrise.

Ring out the old

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The Daresbury laboratory (Credit: STFC Daresbury Laboratory)

By Matin Durrani

Reporting the opening of new facilities is grist to the mill for us on Physics World. That’s why we ran a long article in last month’s print issue about the opening of the new “second target station” at the ISIS pulsed-neutron source at the Rutherford Appleton Laboratory near Oxford in the UK.

The £145m upgrade to the ISIS facility, which is used for a wide range of neutron-scattering experiments, moved a step closer to completion today when the first neutrons were created in the new station.

But spare a thought for the Synchrotron Radiation Source (SRS) at the Daresbury Laboratory in Cheshire, in the north-west of England, which officially closes today after 28 years of operation and two million hours of science.

By Matin Durrani

Who’s the only physicist to have won a Nobel Prize for Literature?

It’s one of those tricky questions that you either know or don’t. And obviously because I know the answer, I couldn’t resist raising it today.

His death last night at the age of 89 has been reported in most media outlets, including the New York Times, which has published a lengthy account of his life.

I’ll drip-feed you a few clues to help you along, if you haven’t got the answer already.

He was born in Kislovodsk in the Caucasus on 11 December 1918, graduating from Rostov University in 1941 with a degree in physics and mathematics.

In February 1945 he was arrested by the Soviet spy agency Smersh and was banged up for eight years in a labour camp.