Category Archive: AQA Unit 1 Particles/ Quantum/ Elec

Nov 22 2013

IceCube detector finds first solid evidence for cosmic neutrinos

IceCube detector finds first solid evidence for cosmic neutrinos

Thu 21 November 2013
Scientists have found the first solid evidence for cosmic neutrinos, ghostly particles created in violent events in the far reaches of the universe.
Neutrinos are subatomic particles that hardly ever interact with the atoms that make up stars, planets and us. Detecting them is tough: in the latest study, researchers detected 28 at the IceCube detector, built under the ice of the south pole.
“This is a huge result. It could mark the beginning of neutrino astronomy,” said Darren Grant, assistant professor of physics at the University of Alberta and one of the leaders of the IceCube Collaboration, which involves more than 250 physicists and engineers from a dozen countries.
Neutrinos are electrically uncharged particles that have a tiny mass, formed in the nuclei of atoms. Travelling at near the speed of light, they hardly interact with anything and could easily fly through a light year of lead. But there are unimaginable numbers of them in the universe: trillions of them from the sun pass through each of us every day.
Scientists know that neutrinos with even higher energy than those already observed should come from cosmic explosions, such as gamma ray bursts, black holes and active galactic nuclei, far away in the universe. Detecting these high-energy neutrinos would give scientists a way to peer inside some of the most violent processes going on at the farthest reaches of the cosmos.
Until now, scientists have used other detectors to see low-energy neutrinos created in cosmic-ray collisions in the Earth’s upper atmosphere and particles from a nearby supernova known as 1987A. The 28 neutrinos detected at IceCube are much higher energy and come from as yet unidentified sources far out in the cosmos. The results were published in the journal Science on Thursday.
“I’ll bet that 20 years from now we’ll look back and say, yeah, this was the start of neutrino astronomy,” John Learned, of the University of Hawaii, Manoa, told Science magazine.
To find the particles, scientists built a detector into a cubic kilometre of ice in Antarctica. After melting holes in the ice, they lowered 86 strings of light detectors, around 5,000 in total, to depths between 1.5km and 2.5km. Neutrinos can interact with atomic nuclei, and when that happens in the ice around a detector the collisions create an avalanche of charged light-emitting particles. That light can be measured by the detectors and, the brighter the light, the more energetic the original neutrino was.
IceCube has been on the hunt for neutrinos since 2010. Since then scientists have found evidence for 28 neutrinos with energies higher than 30 teraelectronvolts (TeV). Two of the particles had energies greater than 1,000 TeV. In comparison, the biggest particle accelerator ever made, the Large Hadron Collider at Cern, will collide particles at 14TeV when its upgrade is completed in 2015.
Since they do not interact with anything, the cosmic neutrinos found at IceCube are useful to scientists because they point in straight lines to where they came from. The few they detected are not enough to pinpoint any location in particular but, according to the project scientist Gregory Sullivan, of the University of Maryland, the IceCube team will look for further detections in coming years, “like waiting for a long exposure photograph”, to fill in their emerging picture of the faraway cosmos.

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Nov 08 2013

Physics probes ‘splashback’ problem

Physics probes ‘splashback’ problem

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Oct 23 2013

The Higgs boson particle – digested

The Higgs boson particle – digested

The Higgs boson particle – digested
The secret of life and the universe, explained by our science editor

An experimental result in the search for the Higgs boson particle, released by Cern.

In the aftermath of the big bang that flung the universe into existence 13.82bn years ago, the forces of nature were one. But as the universe expanded and cooled, they separated out into the four seen today. The electromagnetic force, which is carried by photons, allows you to see, and stops you falling through your chair.

The strong force holds atomic nuclei together. The weak force goes to work in the sun and helps to make it shine. Then there is gravity, which is not really a force at all, but that is for another time.

One trillionth of a second after the big bang, an invisible field that spread throughout space switched on. This Higgs field wrenched two intertwined forces apart – the weak force and the electromagnetic force. How? By making the particles that carry the weak force heavy, while leaving the photon weightless.

The weak force travels less than the width of an atom, but the electromagnetic force ranges over an infinite distance.

The Higgs field gives mass to other particles too, such as quarks and electrons, the building blocks of atoms. The Higgs boson comes with the field, a subatomic smoking gun that proves the field is there.

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Sep 23 2013

New Scientist: Leaky microwaves can power your kitchen gadgets

New Scientist: Leaky microwaves can power your kitchen gadgets.

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Sep 19 2013

T2K neutrino experiment – Super Kamiokande!

T2K neutrino experiment reports new oscillation results


Ben Still, who works on the T2K neutrino experiment in Japan, describes the new result they have reported today at the European Physical Society meeting in Stockholm..

T2K overview

For the first time ever the ghosts of the particle world, neutrinos, have been explicitly seen to actively change personality. Results presented today by the Tokai to Kamioka (T2K) experiment fills in previously unseen parts of the picture of how our universe works at the smallest scales, but it also raises some interesting questions.

Neutrino particles are ghostly, difficult to see, particles that have real personality issues. They come in three types, known as flavours: electron (νe), muon (νμ) and tau (ντ) neutrinos. The first neutrino experiments used naturally occurring sources of the particles, such as the Sun (electron neutrinos) and cosmic ray particle showers (muon neutrinos), to understand more about how they interacted with the world around them. They seemed to be misbehaving according to either experiment or theory as fewer neutrinos were seen than were predicted. For years neutrinos in nature seemed to be disappearing between being created and then detected in many various experiments that looked for them. After almost 30 years of experimentation all was finally resolved. It was proven that naturally occurring neutrinos were not disappearing, but instead were changing into other types of neutrino which could not be seen, due to having too low an energy.

Beams have now been engineered to further investigate this bizarre characteristic now known as oscillation. These beams are specifically muon-type neutrinos because physicists copied cosmic ray particle showers in nature. Experiments saw the muon-type neutrinos disappearing as expected from natural observation. Because of the disappearance they were assumed to be changing into tau-type neutrinos, which did not have enough energy to produce a tau particle and be directly seen.

For the first time neutrinos have actively been seen to change from one flavour to another rather than just viewing a disappearance. The T2K experiment has seen muon neutrinos change character to become electron neutrinos after a journey of 295km across Japan. The certainty of this measurement is quoted as 7.5 standard deviations from zero or to put in terms of percentage over 99.9999999999936% sure that the appearance is occurring.

T2K neutrino eventHistory has shown us that the more we understand about neutrinos the more secrets of nature they uncover. The observation made by T2K opens up a whole new way of observing neutrinos. As we continue to piece together the character of the neutrinos we hope to continue uncovering more bizarre secrets; they may even be the key to how the raw material for the Universe was first created.

Ben Still is a particle physicist at Queen Mary, University of London

More information on the EPS HEP meeting is here, and further details of the presentation can be found here.

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Jul 21 2013

Neutrino ‘flavour’ flip confirmed

Neutrino ‘flavour’ flip confirmed


An important new discovery has been made in Japan about neutrinos. These are the ghostly particles that flood the cosmos but which are extremely hard to detect and study. Experiments have now established that one particular type, known as the muon “flavour”, can flip to the electron type during flight. The observation is noteworthy because it allows for the possibility that neutrinos and their anti-particle versions might behave differently. If that is the case, it could be an explanation for why there is so much more matter than antimatter in the Universe. Theorists say the counterparts would have been created in equal amounts at the Big Bang, and should have annihilated each other unless there was some significant element of asymmetry in play.

“The fact that we have matter in the Universe means there have to be laws of physics that aren’t in our Standard Model, and neutrinos are one place they might be,” Prof Dave Wark, of the UK’s Science and Technology Facilities Council (STFC) and Oxford University, told BBC News. The confirmation that muon flavour neutrinos can flip, or oscillate, to the electron variety comes from T2K, an international collaboration involving some 500 scientists. The team works on a huge experimental set-up that is split across two sites separated by almost 300km. At one end is the Japan Proton Accelerator Research Centre (J-Parc) located on the country’s east coast.

The ‘ghostly’ neutrino particle

  • Second most abundant particle in the Universe, after photons of light
  • Means ‘small neutral one’ in Italian; was first proposed by Wolfgang Pauli in 1930
  • Uncharged, and created in nuclear reactions and some radioactive decay chains
  • Shown to have a tiny mass, but hardly interacts with other particles of matter
  • Comes in three flavours, or types, referred to as muon, tau and electron
  • These flavours are able to oscillate – flip from one type to another – during flight
  • Could be a Majorana particle – that is a particle that is equal to its anti-particle

It generates a beam of muon neutrinos that it fires under the ground towards the Super-Kamiokande facility on the west coast. The Super-K, as it is sometimes called, is a tank of 50,000 tonnes of ultra-pure water surrounded by sensitive optical detectors. These photomultiplier tubes pick up the very rare, very faint flashes of light emitted when passing neutrinos interact with the water.

In experiments in early 2011, the team saw an excess of electron neutrinos turning up at Super-K, suggesting the muon types had indeed changed flavour en route. But just as the collaboration was about to verify its findings, the Great Tohoku Earthquake damaged key pieces of equipment and took T2K offline. Months of repairs followed before the project was able then to gather more statistics and show the muon-electron oscillation to be a formal discovery. Details are being reported on Friday at the European Physical Society Conference on High Energy Physics in Stockholm, Sweden.

“Up until now the oscillations have always been measured by watching the types disappear and then deducing that they had turned into another type. But in this instance, we observe muon neutrinos disappearing and we observe electron neutrinos arriving – and that’s a first,” said Prof Alfons Weber, another British collaborator on T2K from the STFC and Oxford.

Neutrino oscillations are governed by a matrix of three angles that can be thought of as the three axes of rotation in an aeroplane – roll, pitch and yaw. Other research has already shown two of the matrix angles to have non-zero values. T2K’s work confirms that the third angle – referred to as theta-one-three – also has to have a non-zero value.

This is critical because it allows for the oscillations of normal neutrinos and their anti-particles, anti-neutrinos, to be different – that they can have enough degrees of freedom to display an asymmetrical behaviour called charge parity (CP) violation. CP-violation has already been observed in quarks, the elementary building blocks of the protons and neutrons that make up atoms, but it is a very small effect – too small to have driven the preference for matter over anti-matter after the Big Bang. However, if neutrinos can also display the asymmetry – and especially if it was evident in the very massive neutrinos thought to have existed in the early Universe – this might help explain the matter-antimatter conundrum. The scientists must now go and look for it. It is likely, though, that much more powerful neutrino laboratories than even T2K will be needed to investigate the issue.

“We have the idea for a Hyper-Kamiokande which will require an upgrade of the accelerator complex,” Prof Weber told BBC News.

“And in America there’s something called the LBNE, which again would have bigger detectors, more sensitive detectors and more intense beams, as well as a longer baseline to allow the neutrinos to travel further.”

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May 18 2013

Nasa buys into ‘quantum’ computer

Quantum Computer

Nasa buys into ‘quantum’ computer

The machine does not fit the conventional concept of a quantum computer, but makes use of quantum effects

A $15m computer that uses “quantum physics” effects to boost its speed is to be installed at a Nasa facility.

It will be shared by Google, Nasa, and other scientists, providing access to a machine said to be up to 3,600 times faster than conventional computers.

Unlike standard machines, the D-Wave Two processor appears to make use of an effect called quantum tunnelling.

This allows it to reach solutions to certain types of mathematical problems in fractions of a second.

Effectively, it can try all possible solutions at the same time and then select the best.

Google wants to use the facility at Nasa’s Ames Research Center in California to find out how quantum computing might advance techniques of machine learning and artificial intelligence, including voice recognition.

Geordie Rose Chief technology officer, D-wave

University researchers will also get 20% of the time on the machine via the Universities Space Research Agency (USRA).

Nasa will likely use the commercially available machine for scheduling problems and planning.

Canadian company D-Wave Systems, which makes the machine, has drawn scepticism over the years from quantum computing experts around the world.

Until research outlined earlier this year, some even suggested its machines showed no evidence of using specifically quantum effects.

Quantum computing is based around exploiting the strange behaviour of matter at quantum scales.

Most work on this type of computing has focused on building quantum logic gates similar to the gate devices at the basis of conventional computing.

But physicists have repeatedly found that the problem with a gate-based approach is keeping the quantum bits, or qubits (the basic units of quantum information), in their quantum state.

“You get drop out… decoherence, where the qubits lapse into being simple 1s and 0s instead of the entangled quantum states you need. Errors creep in,” says Prof Alan Woodward of Surrey University.

One gate opens…

Instead, D-Wave Systems has been focused on building machines that exploit a technique called quantum annealing – a way of distilling the optimal mathematical solutions from all the possibilities.

Geordie Rose, D-WaveGeordie Rose believes others have taken the wrong approach to quantum computing

Annealing is made possible by physics effect known as quantum tunnelling, which can endow each qubit with an awareness of every other one.

“The gate model… is the single worst thing that ever happened to quantum computing”, Geordie Rose, chief technology officer for D-Wave, told BBC Radio 4’s Material World programme.

“And when we look back 20 years from now, at the history of this field, we’ll wonder why anyone ever thought that was a good idea.”

Dr Rose’s approach entails a completely different way of posing your question, and it only works for certain questions.

But according to a paper presented this week (the result of benchmarking tests required by Nasa and Google), it is very fast indeed at finding the optimal solution to a problem that potentially has many different combinations of answers.

In one case it took less than half a second to do something that took conventional software 30 minutes.

A classic example of one of these “combinatorial optimisation” problems is that of the travelling sales rep, who needs to visit several cities in one day, and wants to know the shortest path that connects them all together in order to minimise their mileage.

The D-Wave Two chip can compare all the possible itineraries at once, rather than having to work through each in turn.

Reportedly costing up to $15m, housed in a garden shed-sized box that cools the chip to near absolute zero, it should be installed at Nasa and available for research by autumn 2013.

US giant Lockheed Martin earlier this year upgraded its own D-Wave machine to the 512 qubit D-Wave Two.

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Apr 17 2013

US team’s battery ‘breakthrough’

US team’s battery ‘breakthrough’

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Apr 17 2013

Physicist’s atom struggles revealed

Physicist’s atom struggles revealed

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Apr 12 2013

New Scientist: Drone-wrecking laser gun to sail on US warship

New Scientist: Drone-wrecking laser gun to sail on US warship.

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Apr 04 2013

Donald Glaser obituary

Donald Glaser Obituary

Scientist who won the Nobel prize for physics in 1960 for the invention of the bubble chamber…..

Donald Glaser, who has died aged 86, won the Nobel prize for physics in 1960 for his invention of the bubble chamber, which made the world of subatomic particles visible and led to many further discoveries. In the 1950s and 60s, before the advent of modern electronics, which dominate high-energy physics today, Glaser’s bubble chamber was one of the most powerful tools for revealing the ephemeral existence of a plethora of subatomic particles. The discovery of hordes of novel particles, whose behaviours showed them to be cousins of the more familiar proton, neutron or pion, revealed that these families are made of more fundamental constituents – the quarks. The quark model has become a foundation of the current “standard model” of the fundamental particles and forces.

Glaser was a 25-year-old faculty member at the University of Michigan when he conceived of the bubble chamber. A homely example of the effect that Glaser developed is that of opening a bottle of beer. Releasing the bottle’s cap causes a sudden drop in pressure, whereby bubbles start to rise through the liquid. Glaser’s idea was to keep a liquid at high pressure, near to its boiling point. In such circumstances, a gentle drop in pressure will cause the liquid to start boiling, an effect well known to mountaineers who, at altitude, can brew a cup of tea at lower temperatures than at sea level.

However, if the pressure drop is sudden, the liquid remains liquid even though it is above its boiling point. This “superheated liquid” is unstable and can be maintained only if left undisturbed.

Glaser’s genius was to realise that if electrically charged particles shoot through a superheated liquid, a trail of bubbles forms as they ionise atoms along their paths. Initially too small to see, they rise up, growing to be large enough to be photographed. The process is very delicate; wait too long and the whole liquid will boil, so Glaser’s idea was to release the pressure and then restore it quickly. Particles entering the liquid during the critical moments of lowered pressure could be photographed.

Initially he made a minute demonstration device, a small glass phial containing a mere 3cl of diethyl ether. This delicate apparatus was able to show the trails left when cosmic rays or particles emitted by a radioactive source passed through.

His idea was, at first, regarded with less than enthusiasm. The US Atomic Energy Commission, and the National Science Foundation, both refused financial support, regarding his scheme as too speculative. His first paper on the subject was apparently rejected because it used the word “bubblet”, which was not in the dictionary. When he asked to speak about his invention at a meeting of the American Physical Society in Washington in April 1953, he received similar lack of enthusiasm, but then had a slice of good fortune.

The organisers had assigned Glaser a slot at the end of the meeting’s final day – a Saturday – when many participants would already have left. On the first day, however, his luck turned by a chance meeting over lunch with Luis Alvarez, a leading nuclear physicist from Berkeley.

Alvarez asked Glaser if he was speaking at the meeting and Glaser said that his 10-minute talk was the final slot when many would have gone home. Alvarez admitted that he too would be unable to be present, and asked Glaser what he was going to report on. Alvarez was immediately impressed, realised that here was a breakthrough, and arranged for a colleague to hear the talk.

In 1959, Glaser moved to Berkeley and the bubble chamber became a practical device in high energy particle physics. It was here that Alvarez’s team developed large versions of Glaser’s device, eventually 2m long, filled with liquid hydrogen, constructed of metal and with glass windows, through which trails of subatomic particles could be photographed. The iconic images adorned the walls of physicists’ offices during the latter half of the 20th century, and the discoveries of particles using this device led Alvarez himself to a Nobel prize.

Glaser was born in Cleveland, Ohio, the son of William, a businessman, and his wife Lena. He received his early education in the public schools of Cleveland Heights, Ohio, and took his BSc in physics and mathematics at the Case Institute of Technology in 1946. After completing his PhD at the California Institute of Technology in 1949, he joined the faculty at Michigan.

After winning the Nobel prize, Glaser shifted his interests to molecular biology, and into applying biotechnology to medicine and agriculture. He also revealed the true version of a popular misconception about his discovery. An oft-told story is that Glaser had his inspiration for the bubble chamber when watching the bubbles rise in a beer glass at the student union. The reality was subtly different. Having made the discovery, and become famous, he would be asked over drinks by colleagues, as if puzzled, what was so profound in such a trivial phenomenon?

He is survived by his second wife, Lynn, whom he married in 1975; and a son, William, and daughter, Louise, from his first marriage, which ended in divorce.

• Donald Arthur Glaser, physicist, born 21 September 1926; died 28 February 2013

• This article was amended on 11 March 2013. The original gave the date of Glaser’s second marriage as 1960. Amendments have also been made to a section on the development of the bubble chamber at Berkeley.

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Apr 04 2013

Dark matter as elusive as ever – despite space station results | Stuart Clark

Dark matter as elusive as ever – despite space station results | Stuart Clark

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Apr 04 2013

LHC to enter ‘new realm of physics’

LHC to enter ‘new realm of physics’

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Mar 27 2013

Synchrotron yields ‘safer’ vaccine

Synchrotron yields ‘safer’ vaccine

Producing vaccines against viral threats is a potentially hazardous business and that’s why manufacturers have to operate strict controls to ensure that no pathogens escape.

British scientists have developed a new method to create an entirely synthetic vaccine which doesn’t rely on using live infectious virus, meaning it is much safer.

What’s more the prototype vaccine they have created, for the animal disease foot-and-mouth, has been engineered to make it more stable.

That means it can be kept out of the fridge for many hours before returning to the cold chain – overcoming one of the major hurdles in administering vaccines in the developing world.

The research, published in the journal PLOS pathogens, was a collaboration between scientists at Oxford and Reading Universities, the Pirbright Institute, and the UK’s national synchrotron facility, the Diamond Light Source near Oxford.

Diamond is a particle accelerator which sends electrons round a giant magnetic ring at near light speeds.

The electrons emit energy in the form of intense X-rays which are channelled along “beamlines” – into laboratories where they are used to analyse structures in extraordinary detail.


Synchrotrons have been used before to analyse viruses at the atomic level, but the technology has advanced considerably to enable scientists to create a stable synthetic vaccine.

“What we have achieved here is close to the holy grail of foot-and-mouth vaccines.

Unlike traditional vaccines, there is no chance that the empty shell vaccine could revert to an infectious form,” said Dave Stuart, Life Sciences Director at Diamond, and MRC Professor of Structural Biology at the University of Oxford.

“This work will have a broad and enduring impact on vaccine development, and the technology should be transferable to other viruses from the same family, such as poliovirus and hand-foot-and-mouth disease, a human virus which is currently endemic in South-East Asia.”

These human disease threats, like foot-and-mouth, are all picornaviruses.

Viruses are inherently unstable and fragile, but picornaviruses can be studied using X-ray crystallography.

Diamond Light Source The Crystal Lab uses robots

This enables the protein shell of the virus to be analysed at the atomic level – something a billion times smaller than a pinhead.

As with any vaccine, the aim is to prompt the immune system to recognise this outer shell and destroy the pathogen before it has time to lock onto cells and infect them with its genetic material.

In this research the scientists created a synthetic viral shell, but lacking its pathogenic RNA interior – the genetic material the virus uses to replicate itself.

Crucially they were able to reinforce the structure of the viral shell to make it stronger, to improve the stability of the vaccine.

Pre-clinical trials have shown it to be stable at temperatures up to 56C for at least two hours. Foot-and-mouth is endemic in central Africa, parts of the Middle East and Asia, so this would be a significant improvement over existing vaccines.

With current foot-and-mouth vaccines it is difficult to distinguish between immunised livestock and those which have been infected.

That proved to be a major hurdle in controlling the foot-and-mouth outbreak in the UK in 2001 because it would have prevented the export of livestock.

But the synthetic vaccine should allow scientists to show the absence of infection in vaccinated animals.

“The foot-and-mouth-disease virus epidemic in the UK in 2001 was disastrous and cost the economy billions of pounds in control measures and compensation,” explained Dr Bryan Charleston, Head of Livestock Viral Diseases Programme at the Pirbright Institute.

“This important work has been a direct result of the additional funding that was provided as a result of the 2001 outbreak to research this highly contagious disease.”

The potential hazards of working with viruses was underlined in 2007 when the Pirbright laboratory site was identified as the source of a leak which led to an outbreak of foot-and-mouth disease.

Polio, another picornavirus, which exclusively affects humans, has been eliminated from nearly every country in the world, although it stubbornly persists in Nigeria, Pakistan and Afghanistan.

The need for secure vaccine production will become even more vital should polio be wiped out.

“Current polio vaccines, which use live virus for their production, pose a potential threat to the long-term success of eradication if they were to re-establish themselves in the population.

“Non-infectious vaccines would clearly provide a safeguard against this risk”, said Dr Andrew Macadam, a virologist specialising in polio at the National Institute for Biological Standards and Control in Hertfordshire.

“This technology has great potential in terms of cost and biosafety.

“Any design strategy that minimises the chances of accidental virus release would not only make the world a safer place but would lower the bio-containment barriers to production allowing vaccines to be made more cheaply all over the world.”

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Mar 21 2013

Planck telescope maps light of the big bang scattered across the universe

Planck telescope maps light of the big bang scattered across the universe

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