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hadron collider
A major upgrade for the Large Hadron Collider (LHC), which is already known for its cutting-edge science, has begun.
Engineers work should double the energy of the LHC, already the most powerful particle accelerator in the world.
Scientists believe the upgrade will enable them to discover new particles which will lead to a more complete theory of how the Universe works.
Scientists believe the LHC upgrade will enable them to discover new particles which will lead to a more complete theory of how the Universe works
The engineers’ tasks also include testing and replacing some of the LHC’s main dipole and quadrupole magnets, which are used to bend the paths of the particles and keep them tightly bunched; conducting tests to detect any irregularities in the magnets or imperfections in the electrical insulation; and a range of other work to improve the machine.
The LHC upgrade will enable it to discover new particles leading to a radical change in our understanding of how the Universe works.
The discovery of Higgs particle last year was the end of a successful chapter of late 20th Century physics.
This was the development of the current theory in the 1960s and 70s called the “Standard Model”.
This theory says that most of the forces of nature, the objects around us and our own existence, are all down to the interaction of the Higgs with 16 other particles. It successfully explains how electricity, magnetism and light operate.
Since then, all the particles predicted by the Standard Model have been discovered – including most recently the Higgs.
The problem though is scientists known this theory is limited. It explains extremely well the world around us, but it cannot explain the way most of the Universe behaves.
Physicists hope that by operating at full power, the LHC will be able to find evidence of so-called supersymmetric particles. These are like the particles in the Standard Model – but more massive.
One form of supersymmetry predicts that there should be five Higgs bosons, which are each slightly different.
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Large Hadron Collider (LHC) scientists have announced that the particle outlined in July 2012 looks increasingly to be a Higgs boson.
Higgs boson, long theorized as the means by which particles get their mass, had been the subject of a decades-long hunt at the world’s particle accelerators.
Yet there is still some uncertainty as to whether the particle is indeed a Higgs boson, and if so, what type it is.
Results at the Moriond meeting in Italy suggest strongly that the particle’s “spin” is consistent with a Higgs.
Teams from the two Higgs-hunting experiments, Atlas and CMS, analyzed two-and-a-half times more data than were available in July in an effort to pin down not only the particle’s existence, but also something about its character.
All that is conclusively established is that the particle is in the family of bosons, but researchers had been careful since July to describe it as “Higgs-like”.
The zoo of subatomic particles are characterized by properties including their “spin” and “parity” – and the precise establishment of these properties for the new particle will determine if it is beyond doubt the long-sought Higgs.
What is more, theories predict that a number of different types of Higgs may exist.
The simplest form – that which fits neatly into the existing Standard Model of particle physics – would surely shore up the theory, but the possible existence of more “exotic” versions of the particle would open exciting new vistas in science.
LHC scientists have announced that the particle outlined in July 2012 looks increasingly to be a Higgs boson
“This is the start of a new story of physics,” said Tony Weidberg, Oxford University physicist and a collaborator on the Atlas experiment.
“Physics has changed since July the 4th – the vague question we had before was to see if there was anything there,” he said.
“Now we’ve got more precise questions: is this particle a Higgs boson, and if so, is it one compatible with the Standard Model?”
The results reported at the conference – based on the entire data sets from 2011 and 2012 – much more strongly suggest that the new particle’s “spin” is zero – consistent with any of the theoretical varieties of Higgs boson.
“The preliminary results with the full 2012 data set are magnificent and to me it is clear that we are dealing with a Higgs boson, though we still have a long way to go to know what kind of Higgs boson it is,” said CMS spokesperson Joe Incandela.
As is often the case in particle physics, a fuller analysis of data will be required to establish beyond doubt that the particle is a Higgs of any kind.
However, Dr. Tony Weidberg said that even these early hints were compelling.
“This is very exciting because if the spin-zero determination is confirmed, it would be the first elementary particle to have zero spin,” he said.
“So this is really different to anything we have seen before.”
Even more data will be required to explore the question of more “exotic” Higgs particles.
A popular but as-yet unsubstantiated theory called supersymmetry suggests there should be as many as five Higgs particles – a notion that will have to remain speculative at least until new data are acquired after the LHC’s two-year shutdown for refurbishment.
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Scientists say they may be able to determine the eventual fate of the cosmos as they probe the properties of the Higgs boson.
A concept known as vacuum instability could result, billions of years from now, in a new universe opening up in the present one and replacing it.
It all depends on some precise numbers related to the Higgs that researchers are currently trying to pin down.
A “Higgs-like” particle was first seen at the Large Hadron Collider (LHC) last year.
Associated with an energy field that pervades all space, the boson helps explain the existence of mass in the cosmos. In other words, it underpins the workings of all the matter we see around us.
Since detecting the particle in their accelerator experiments, researchers at the Geneva lab and at related institutions around the world have begun to theorize on the Higgs’ implications for physics.
One idea that it throws up is the possibility of a cyclical universe, in which every so often all of space is renewed.
“It turns out there’s a calculation you can do in our Standard Model of particle physics, once you know the mass of the Higgs boson,” explained Dr. Joseph Lykken.
“If you use all the physics we know now, and you do this straightforward calculation – it’s bad news.
“What happens is you get just a quantum fluctuation that makes a tiny bubble of the vacuum the Universe really wants to be in. And because it’s a lower-energy state, this bubble will then expand, basically at the speed of light, and sweep everything before it,” said the Fermi National Accelerator Laboratory theoretician.
It was not something we need worry about, he said. The Sun and the Earth will be long gone by this time.
Scientists say they may be able to determine the eventual fate of the cosmos as they probe the properties of the Higgs boson
Dr. Joseph Lykken was speaking here in Boston at the annual meeting of the American Association for the Advancement of Science (AAAS).
He was participating in a session that had been organized to provide an update on the Higgs investigation.
The boson was spotted in the wreckage resulting from proton particle collisions in the LHC’s giant accelerator ring.
Data gathered by two independent detectors observing this subatomic debris determined the mass of the Higgs to be about 126 gigaelectronvolts (GeV).
That was fascinating, said Prof. Chris Hill of Ohio State University, because the number was right in the region where the instability problem became relevant.
“Before we knew, the Higgs could have been any mass over a very wide range. And what’s amazing to me is that out of all those possible masses from 114 to several hundred GeV, it’s landed at 126-ish where it’s right on the critical line, and now we have to measure it more precisely to find the fate of the Universe,” he said.
Prof. Chris Hill himself is part of the CMS (Compact Muon Solenoid) Collaboration at the LHC. This is one of the Higgs-hunting detectors, the other being Atlas.
Scientists have still to review about a third of the collision data in their possession. But they will likely need much more information to close the uncertainties that remain in the measurement of the Higgs’ mass and its other properties.
Indeed, until they do so, they are reluctant to definitively crown the boson, preferring often to say just that they have found a “Higgs-like” particle.
Frustratingly, the LHC has now been shut down to allow for a major programme of repairs and upgrades.
“To be absolutely definitive, I think it’s going to take a few years after the LHC starts running again, which is in 2015,” conceded Dr. Howard Gordon, from the Brookhaven National Laboratory and an Atlas Collaboration member.
“The LHC will be down for two years to do certain repairs, fix the splices between the magnets, and to do maintenance and stuff. So, when we start running in 2015, we will be at a higher energy, which will mean we’ll get more data on the Higgs and other particles to open up a larger window of opportunity for discovery. But to dot all the I’s and cross all the T’s, it will take a few more years.”
If the calculation on vacuum instability stands up, it will revive an old idea that the Big Bang Universe we observe today is just the latest version in a permanent cycle of events.
“I think that idea is getting more and more traction,” said Dr. Joseph Lykken.
“It’s much easier to explain a lot of things if what we see is a cycle. If I were to bet my own money on it, I’d bet the cyclic idea is right,” he said.
Scientists at the Large Hadron Collider (LHC) are expected to reveal the strongest evidence yet for the Higgs particle in Geneva, Switzerland, shortly.
Anticipation is high and rumors have been rife about the announcement.
The Higgs boson would help explain why particles have mass, and fills a glaring hole in the current best theory to describe how the Universe works.
The strength of the LHC’s signal is understood to be just short of the benchmark for claiming a “discovery”.
But it will show that researchers are now tantalisingly close to confirming the Higgs’ existence and bringing to an end the decades-long quest for the most coveted prize in physics.
The $10 billion LHC is the most powerful particle accelerator ever built: it smashes two beams of protons together at close to the speed of light with the aim of revealing new phenomena in the wreckage of the collisions.
But why has so much time and effort been invested in detecting the boson?
Mass is a measure of how much stuff an object – such as a particle or molecule – contains. If it were not for mass, all of the fundamental particles that make up atoms would whiz around at light-speed and the Universe as we know it would never have clumped into matter.
The Higgs boson would help explain why particles have mass, and fills a glaring hole in the current best theory to describe how the Universe works
According to the theory, all of space is filled by a field – known as the Higgs field, which is mediated by particles known as Higgs bosons.
Other particles gain mass when they interact with the field, much as a person feels resistance from the water – drag – as they wade through a swimming pool.
The boson is the last missing particle in the Standard Model, the most widely accepted theory of how the cosmos works. But the Higgs remains a theoretical construct that has never been observed in a particle accelerator.
Four of the six theoretical physicists credited with coming up with the Higgs mechanism in the 1960s – including Prof Peter Higgs, after whom it is named – have been invited to CERN in Geneva for the presentations, fuelling anticipation of a major announcement.
Unconfirmed reports suggest that the signal detected at a mass of 125 gigaelectronvolts (GeV), which was announced in December, has since strengthened.
“We now have more than double the data we had last year,” said CERN’s director for research and computing, Sergio Bertolucci.
“That should be enough to see whether the trends we were seeing in the 2011 data are still there, or whether they’ve gone away. It’s a very exciting time.”
Discovering particles is a numbers game, and scientists analyze many events that could be representative of a Higgs boson being produced in the LHC.
The hints of the Higgs revealed in 2011 had a statistical certainty of just two sigma.
Three sigma represents about one in 700 likelihood that a “bump” in the data is down to some statistical fluctuation, in the absence of a Higgs. But the benchmark for a discovery is five sigma, denoting a one-in-3.5 million likelihood that a result is down to such a fluctuation.
Rumors suggest the certainty level has now crept beyond four sigma. This might not be enough to announce that scientists have found the elusive particle. But it would suggest the LHC’s scientists are within touching distance, and several physicists privately say that such a signal is now unlikely to go away.
Also, the idea that some systemic error could affect all the experiments that see hints of the Higgs – including those at the LHC and the US Tevatron machine (which search for the particle in different ways) – seems just as improbable.
But if and when a new particle is discovered, it will not be clear straight away that it is the Higgs. Physicists will need to characterize its properties in order to confirm whether it is the version of the Higgs predicted by the Standard Model, a “non-conformist” Higgs that hints at new laws of physics, or something else entirely.
This will involve years of detailed and difficult work, said Dr. Tony Weidberg, a University of Oxford physicist and member of one of the LHC’s experimental teams, Atlas.
He said that even at a certainty level of five sigma, “you’re very far from proving it’s a Higgs particle at all, let alone a Standard Model Higgs”.
