Particle Consistent with the Higgs Boson Discovered at the LHC

By Stephen Sadler

On Wednesday, in a seminar watched live on the Internet all around the world, scientists from the two main detectors at CERN’s Large Hadron Collider (LHC) in Geneva announced the discovery of a new particle whose properties are consistent with the long sought-after Higgs boson.

The Higgs is the fundamental particle responsible for providing all other particles with mass, and represents the final missing piece of the Standard Model of particle physics. Its existence was proposed in 1964 by three groups independently: Peter Higgs; Robert Brout and Francois Englert; and Gerald Guralnik, C.R. Hagen and Tom Kibble, and in 2010 the six physicists were jointly awarded the J.J. Sakurai Prize for Theoretical Particle Physics for their work.

Candidate Higgs event recorded by the CMS detector in May 2012. This event exhibits the characteristics expected from a Standard Model Higgs (not seen) decaying into two photons (yellow dashes and green bars).

In Wednesday’s seminar, CMS spokesman Joe Incandela and ATLAS spokeswoman Fabiola Gianotti announced that both of their experiments had detected a new particle with a significance of 5 sigma, which corresponds to a 1 in 3.5 million chance that the result is in fact a statistical fluke. This is the benchmark in the field for claiming the discovery of a new particle.

“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 Gianotti.

Scientists at the University of Sheffield have played a key role in both engineering and data analysis for the ATLAS detector, as well as providing supercomputers for the worldwide particle physics computing network known as the Grid.

CERN Director General Rolf Heuer had this to say about the new discovery:

“We have reached a milestone in our understanding of nature. 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.”

Hydrogen-powered Robojelly preparing for maiden voyage

By Holly Rogers

A robotic jellyfish made of smart materials could be used in search and rescue operations, say researchers from Virginia Tech.

The tentacled creation, known as Robojelly, is made from a collection of materials that change shape or size to match their environment, held in place with carbon nanotubes. As well as its intelligent build, it could theoretically run forever – the clever cnidaria is powered entirely by hydrogen.

“To our knowledge, this is the first successful powering of an underwater robot using external hydrogen as a fuel source”, said Yonas Tadesse, the lead author of the study.

Robojelly is made from “shape memory alloys”, which are smart materials that remember their original shape. These materials are wrapped in carbon nanotubes and coated in platinum powder, which is the key to the fuel source. The platinum powder reacts with oxygen and hydrogen from the surround water and produces heat, which powers the robot’s movements.

Its swimming technique mimics that of a jellyfish – the “bell” chamber  fills with water, which then collapses, forcing the water out and driving the body forwards. In jellyfish, this is done with muscle contractions, but Robojelly makes use of heat produced by the fuel cell to transform its smart material body. However, although Robojelly has been successfully tested in a water tank, it’s not quite ready for service yet. Developers need to add individual controls to each segment of the robot, which will allow it to be steered in different directions. Until then, it can be seen in testing phase below:

 

 

Y. Tadesse, A. Villanueva, C. Haines, D. Novitski, R. Baughman and S. Priya, Hydrogen-fuel-powered bell segments of biomimetic jellyfish, Smart Materials and Structures, 21, 2012.

The paper can be found at: http://iopscience.iop.org/0964-1726/21/4/045013

End of the Line for Superluminal Neutrinos?

By Stephen Sadler

Physicists were shocked last September when a paper published by the OPERA collaboration suggested that neutrinos in their detector in the Gran Sasso underground lab in Italy had been caught travelling faster than the speed of light. If correct, the result calls into question Einstein’s Theory of Relativity, and open the door to all sorts of weird and wonderful effects such as the reversal of causality and time travel. In fact, so perturbed were the researchers at the implications of their results, that they delayed publishing their findings for 5 months while they meticulously checked the experiment for errors, before finally concluding that they could do no more without the help of the wider particle physics community.

Unsurprisingly, interest has been huge, and as of today (February 26th 2012) a search of the keywords ‘superluminal neutrino’ on arXiv.org yields 163 papers on the subject. However, despite the focused attention of some of the world’s top minds, until recently no mistakes in the experimental method or data analysis had come to light. Indeed, the OPERA collaboration repeated their experiment with a neutrino beam configuration that allows for more precise timing, and found the same effect. Many scientists still doubted the result though, and last December Ramanath Cowsik, professor of physics in Arts & Sciences and director of the McDonnell Center for the Space Sciences at Washington University in St. Louis, and his team of collaborators pointed out a glaring problem which had been overlooked.

Neutrino beams for particle physics experiments are produced in a three-step process that begins by accelerating protons to 99.9999991% the speed of light, in an accelerator such as the Large Hadron Collider at CERN in Switzerland. These ultra-relativistic protons are then smashed into a graphite target producing, amongst other debris, secondary particles called pions. Finally, these short-lived pions are focussed into a tight beam by magnetic horns before they quickly decay into a beam of neutrinos and charged sister particles of the electron called muons, each of which carries off some fraction of the total pion momentum. Finally a ‘beam dump’ at the end of the decay pipe stops all particles other than the neutrinos, leaving a pure neutrino beam.

The trouble is that in order to produce the high energy neutrinos observed at OPERA, the fraction of momentum carried off by the neutrinos needs to be less than about 0.05. This, in turn, implies that the decaying pions must have an extremely high momentum, and Einstein’s theory of relativity tells us that this very high momentum would extend the pions’ lifetime so much that they would not have time to decay in the beam pipe at CERN before smashing into the concrete beam dump.

“We’ve shown in this paper that if the neutrino that comes out of a pion decay were going faster than the speed of light, the pion lifetime would get longer, and the neutrino would carry a smaller fraction of the energy shared by the neutrino and the muon,” Cowsik says. “So we are saying that in the present framework of physics, superluminal neutrinos would be difficult to produce.”

Now, it seems as though Cowsik was right to be skeptical, as an email from CERN Director General Rolf Heuer to CERN staff last week announced that the OPERA collaboration had identified two possible sources of error in their neutrino velocity measurement. The first has to do with an oscillator used in the timing system of the experiment, and could only increase the size of the faster-than-light effect. The second, though, concerns a potentially faulty optical fibre connection that sends an external GPS signal to the OPERA master clock, and could serve to bring the velocity of the neutrinos back down to the sub-light-speeds physicists are used to.

The OPERA collaboration have fixed the problems and are now in the process of determining the effect they may have had on the results. New data taken with the repaired detector is expected in May, but for now scientists around the world are applauding the OPERA team for the open and transparent way in which they have reported their surprising result. In an interview for BBC News Sergio Bertolucci, director of research at CERN, said “One has to realise that the collaboration has never stopped to try to ‘kill’ the measurement (proving that it was erroneous)”. Even if the result turns out to be a false alarm due to loose wiring, the story has been a textbook example of good scientific practice.

The paper announcing the superluminal measurement can be found at:  http://arxiv.org/abs/1109.4897, whilst a preprint of Cowsik’s work detailing the problems raised by pion decay kinematics appears here: http://arxiv.org/abs/1110.0241v2.

What Causes a Static Shock?

Once again I was called upon for the public service of South Yorkshire and to help out Michelle Mustard on Hallam FM find an answer to a question that had been bugging her all week: What causes static shocks and how can you avoid them?

To understand what causes static shocks, those annoying zaps that seem to come from seemingly innocuous objects without warning, we have to look at what the universe and everything in it is made of.

Atoms, which are the building blocks for all matter in the universe, are made up themselves of particles that look this:

The centre, or nucleus, of the atom has electrons zipping around the outside. These electrons have a negative charge (think electricity).  Any time two surfaces come in to contact with each other electrons are exchanged. Some materials are more likely to lose their electrons from their surfaces and others are more likely to gain electrons.

Ultimately this means that the material that has gained the electrons will have more of a negative charge. If these ions (charged particles) cannot move because the material doesn’t conduct electricity (i.e., it’s an insulator) then those electrons hang about (literally they are static, in the sense that they don’t move).

That is until something that DOES conduct electricity comes in to contact with them, this is any conductor that is ‘earthed’, so that the electrons can flow from the insulator through to earth. This usually isn’t a massive energy, but because it happens over such a short amount of time it can sometimes look like a spark of electricity, and more often than not is felt as a little shock.

So I’m painting this as harmless, but these are the babies of the daddies of static shocks: lightning. Static electricity builds up in big storm clouds where ice has formed and the particles rub against each other until the charge has built up to such an extent that it can no longer be contained and draws up positive ion streamers from the ground – when the negative and positive streamers meet the ions are discharged with such power that they super-heat the air creating light (lightning) and the air expands so quickly from the heat that it causes a a loud sound wave to be produced (thunder).

And it doesn’t end there… flour, as you may or may not know, is highly explosive. There have been recorded instances where a spark arising from static charge building up in grain silos where flour dust particles have rubbed against each other have actually caused massive and seemingly spontaneous explosions.

How do you avoid getting static shocks then? Well my advice is to not drag your feet on carpets, especially in those generic flat, sheep-skin boots, and then touch taps, radiators, or any other metallic, earthed object. Secondly, avoid travellators and escalators (those rubber handles brushing against the metal…) and finally avoid synthetic fibres, or at least rubbing around in them too much.

Study Scientifique

And for my first trick… let me bring your attention to Study Scientifique, a post I did for the Craft Candy blog last year. The Art-Science Adventures blog will catalogue the crafty side of science  – be it oversized stuffed microbes, DNA-banded bangles or crochet crystal structures. Check back here for featured DIY projects and tutorials, downloadable freebies, new and noteworthy articles, and excellent one-of-a-kind gift ideas for Scientists.