Physics

By Joseph Milton, FT science intern

The “discovery” of dark matter – the hypothetical, undetectable substance thought to make up around a quarter of the contents of the universe and the majority of the matter in it – has been covered in some newspapers and websites today.

But, while the confirmation of dark matter’s existence would certainly be big news, the media may be over-egging this discovery.

Thought to provide a kind of “gravitational scaffolding” which supports normal matter, dark matter has eluded detection since its existence was first posited by Fritz Zwicky in 1933.

Since 2003 a team of US scientists has been deep underground in the disused Soudan mine, northern Minnesota, working on the Cryogenic Dark Matter Search (CDMS).

Using a bank of 30 detectors made of germanium and silicon, cooled to temperatures very near absolute zero (−273 degrees Celsius), they have been looking for energy signatures indicative of dark matter.

A cryostat (cooled detector chamber) with detector assembly installed at Soudan Mine

A cryostat (cooled detector chamber) with detector assembly installed at Soudan Mine

Physicists think dark matter could be composed of weakly interacting massive particles, or WIMPs for short. In theory, these particles don’t absorb or emit light and have a mass similar to that of an atomic nucleus.

Scientists think WIMPs may occasionally “bounce off” atomic nuclei, leaving behind an energy trace – the signature the scientists have been looking for.

The CDMS team announced yesterday evening that they had detected two events, or energy signatures, consistent with WIMPs “bouncing off” nuclei.

But Pierre Oddone, director of the Department of Energy’s Fermi National Accelerator Lab (Fermilab) near Chicago, stressed that he could not be sure that what they had detected was the signature of dark matter.

“While this result is consistent with dark matter, it is also consistent with backgrounds,” he said, suggesting that both signatures could have been caused by natural radiation, or by cosmic rays from space.

The rationale behind placing the detectors half a mile underground under layers of shielding materials is to suppress such unwanted interference, but these background events are still periodically detected.

During a seminar at Fermilab, Dan Bauer, head of the CDMS, said there was a one in four chance that the detected signatures were background events, and a later statement from the team reiterated that “we can make no claim to have discovered WIMPs.”

What they have discovered is that the frequency of interactions between the elusive WIMPs and atomic nuclei – the “bouncing” events which leave the energy signatures and which the scientists are looking for – may be lower than was previously thought, as theoretically predicted by the mass of WIMPs. To confuse matters further, assumptions about the mass of WIMPs are also theoretical calculations.

These experiments gave the scientists a more accurate estimate of the frequency of such interactions, and the researchers said they might therefore be useful in eliminating a number of other competing theories which attempt to explain dark matter.

They went on to say that they would have to detect at least five events to be sure they were looking at dark matter signatures. To try and achieve this the team will upgrade their detectors next year and continue the search for WIMPs.

It seems the scientists have been considerably more cautious in their statements about the significance of these results than some journalists – quelle surprise.

By Joseph Milton, FT science intern

Lord Drayson, science minister, may consider restructuring one of the government’s largest science and technology funding agencies after it was forced to withdraw 25 per cent of its studentships and fellowships following budget cuts.

In 2010-11 the Science and Technology Facilities Council (STFC) will have to survive on £20m less than the current year’s budget, and it has also been hit hard by currency fluctuations.

The devaluation of the pound has meant that subscriptions to international organisations, such as the European Organization for Nuclear Research (CERN) and the European Southern Observatory (ESO), account for a much larger proportion of the STFC’s budget for next year – around 50 per cent of the total. But the council feels that membership of these organisations is worth the money spent.

The results for other areas funded by the STFC will include the 25 per cent cut in funding for researchers, and the end of a number of science projects based in the UK.

Nuclear physics was hit particularly hard, but astronomy, particle physics and space science will also have to absorb cuts. The STFC proposed “managed withdrawals” from a number of existing scientific ventures.

Scientists were dismayed by the news. Paddy Regan, a nuclear physicist at the University of Surrey, said the cuts “have the potential to kill off the UK skills base in nuclear physics…To have this at a time when the UK is discussing a nuclear new build programme… is almost comical.”

The STFC is a strangely structured beast. It was formed in 2007 through a merger of two other research councils which dealt with particle physics and astronomy, and also took responsibility for nuclear physics from a third council.

It is responsible for funding research students and fellows in these areas, as well as maintaining UK scientific facilities such as ISIS – a pulsed neutron and muon source – and the Central Laser Facility, both in Oxfordshire, and for paying subscription charges for memberships of international organisations.

Because the value of the pound is completely beyond the control of the council, and because it is understandably keen to retain membership of international organisations, devaluation will inevitably lead to the areas it can control, such as studentships, losing out disproportionately.

Lord Drayson said that he was keen to find a way round the cuts in a press release issued today in response to the STFC budget announcements, but he is very unlikely to be able to come up with any more money.

Instead he seems to be proposing a restructuring: “There are real tensions in having international science projects, large scientific facilities and UK grant giving roles within a single research council,” he says, and adds, “I will work urgently with the STFC and the wider research community to find a better solution by the end of February 2010.”

That suggests that the STFC’s days, at least in its current form, may be numbered.

Clive Cookson

Engineers at Cern near Geneva hope to restart the Large Hadron Collider, the world’s most powerful atom smasher, this weekend.

Understandably it will be a low-key affair, with the media not invited, in contrast to the razzmatazz of the original start-up in September 2008. Nine days later the $8bn LHC suffered a serious electromagnetic failure and it has been shut down ever since, as Cern carried out comprehensive repairs and installed new safety equipment.

Cern engineers repair a damaged magnet

Cern engineers repair a damaged magnet

If final checks are satisfactory, Cern engineers will send proton beams round the 27km LHC underground ring tomorrow at fairly low energy, first in one direction and then in the other.

They may carry out some collisions between beams before Christmas, again at relatively low energy. But the moment Cern calls “first physics” – the first high-energy collisions that could produce interesting scientific results – is unlikely to come until January. And Cern has promised to invite some journalists then, though there may not be more than a day or two’s notice.

Clive Cookson

The restart date for CERN’s Large Hadron Collider, the world’s most expensive physics machine, has slipped yet again. The Geneva-based organisation said last night that the LHC would start up in November – and run at a lower power than originally planned.

The LHC suffered a catastrophic short-circuit last September, just days after its triumphant opening ceremony and before physicists could use it to do any real experiments.

Since then CERN engineers have been scrutinising every electrical connection and every magnet in the collider’s 27km underground ring – and finding a disconcerting number of faults. That required several slippages in the restart schedule.

Now Rolf Heuer, CERN’s director-general, is going for a date in November. “The LHC is a much better understood machine than it was a year ago,” he says. “We can look forward with confidence and excitement to a good run through the winter and into next year.”

The initial operating power will be 3.5 TeV, half the original specification. But it will still be much higher than any previous atom smasher – and should be enough to give the thousands of physicists waiting to work on the LHC a new glimpse into the fundamental forces and particles that make up our universe.

The world of research

The science blog is no longer updated but it remains open as an archive.

Clive Cookson, the FT's science editor, picks out the research that everyone should know about, in fields from astronomy to zoology. He also discusses key policy issues, from R&D funding to science education. He'll cover the weird and wonderful, as well as the serious side of science.

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