Friday, July 20, 2012

Coming slip events cast their electrical shadows

It has long been said that coming events cast their shadows before. Forecasting disasters has long been the mainstay of oracles, soothsayers and astrologers. Unfortunately, all the aforementioned are about to be out of work. Scientists have found clues which can help to predict disasters, at least of the kind that can be classified as slip events. Avalanches, earthquakes and fractures frequently occur as a consequence of surfaces sliding on each other and undergoing a sudden slip, and are considered to be examples of slip events.

N. Nirmal Thyagu, an alumnus of IIT Madras, now at the University of Rutgers, and coworkers Troy Shinbrot and Nam H. Kim, found that  packing granular powders in a rotating cylinder gives rise to avalanche events, a fact which is well known to those who study granular media.
The bursts originate from tiny flaws in the structure of the densely packed powder which propagate towards the surface as the cylinder revolves, eventually resulting in a crack that shears off a portion of the powder from the main body. However, the new discovery came when they stuck a voltage probe inside the powder, (Tylenol, in case anyone is giving themselves a headache identifying the powder), having first cleared the cylinder of static electricity. The probe recorded a voltage spike as considerable as 100 volts, about five seconds before the actual avalanche, or slip event occurs. These five seconds, by which the precursor event (the voltage spike) precedes the actual event (the avalanche), should be compared with the time scale of the avalanche itself, which lasts about 19 seconds. Troy Shinbrot, who led the group, got this idea from earthquake folklore, which has always told stories of lightning and other electrical disturbances preceding earthquakes. The table top experiment set up at Rutgers confirmed this. Similar prediction is possible for events that involve the  impending failure of granular materials, as in cascades in silos, concrete bridge collapses, and  perhaps even earthquakes. 

Journal reference:  Proceedings of the Natural Academy of sciences, DOI: 10.1073/pnas.1121596109

Popular articles: Science News, New Scientist, Phys. Org.

This blog post is by Neelima Gupte and Sumathi Rao.

Wednesday, July 4, 2012

The Higgs is here

As promised, here is the upshot of today's press conference at CERN. They did stick their necks out after all, although with caveats and caution, as befitting careful experimental physicists. The press release said, “We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV. The outstanding performance of the LHC and ATLAS and the huge efforts of many people have brought us to this exciting stage,” said ATLAS experiment spokesperson Fabiola Gianotti,“but a little more time is needed to prepare these results for publication.”

 The spokesperson for the other experiment was equally clear and equally cautious. "The results are preliminary but the 5 sigma signal at around 125 GeV we’re seeing is dramatic. This is indeed a new particle. We know it must be a boson and it’s the heaviest boson ever found,” said CMS experiment spokesperson Joe Incandela.“The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks."

There is no doubt that a new boson has been found, with Higgs like properties. The magic number 5 sigma is found by combining more than one decay mode, which some people cavil at. This may be the Standard model Higgs, or it may have properties beyond the Standard model. However, the bottom line is exactly what the Director General of CERN said. “We have reached a milestone in our understanding of nature,” said CERN Director General Rolf Heuer. “The discovery of a particle consistent with the Higgs boson opens the way to more detailed studies, requiring larger statistics, which will pin down the new particle’s properties, and is likely to shed light on other mysteries of our universe.”

This blog post is by Neelima Gupte and Sumathi Rao.

So there were fireworks on the 4th of July, after all!

 Tailpiece: A Higgs boson walks into a bar, and slaps a large denomination Euro note on the counter. `A big one', it says, ' I've been discovered'.  The bar tender says, `Are you the one they've been looking  for?' `Who cares? ' sniffs the boson. `If I'm not the one, it's even better'.

@ Rahul Siddharthan: Take a look at this link We blogged a lot on the Higgs last year, and a great deal of the story is here, jokes and all.

Slouching towards Eureka

Today might be Eureka day, i.e. CERN might announce the discovery of the Higgs particle.  Or instead, they may announce better bounds and non- Standard Model physics! Fermilab yesterday confirmed that a detailed analysis of their Tevatron data supports strongly (2.9 sigma) all the indications that the Higgs is lurking in the expected range (115-135 GeV) via b-b-bar decays , but no one has the magic 5 sigma result yet.

Meanwhile particle physicists are all excited and waiting for the web-cast from CERN. Hopefully it will be a faster than the December one. In case you want a blow by blow account, here is the link to the Cosmic Variance blog from Discover magazine.

More later today, when we find out  the real score.

5 sigma result at 125 GeV! Is this it? 

This blog post is by Neelima Gupte and Sumathi Rao.