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Posts tagged "LHC"

christinetheastrophysicist:

Physicists plan to build a bigger LHC

When Europe’s Large Hadron Collider (LHC) started up in 2008, particle physicists would not have dreamt of asking for something bigger until they got their US$5-billion machine to work. But with the 2012 discovery of the Higgs boson, the LHC has fulfilled its original promise — and physicists are beginning to get excited about designing a machine that might one day succeed it: the Very Large Hadron Collider (VLHC).

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sagansense:

Supercharging the search for secrets of the universe

image 1: The Large Hadron Collider at CERN faces a two-year shutdown so engineers can ramp up its maximum energy.
image 2: Proton-proton collisions during the search for the Higgs boson. Photo: AFP
image 3: A collision event between two lead ions in the Large Hadron Collider as observed by the ALICE detector. Photo: Supplied
image 4: A simulated black hole created by the Large Hadron Collider. Photo: Supplied

When it comes to shutting down the most powerful atom smasher ever built, it’s not simply a question of pressing the off switch.

In the French-Swiss countryside on the far side of Geneva, staff at the Cern particle physics laboratory are taking steps to wind down the Large Hadron Collider. After the latest run of experiments ends next month, the huge superconducting magnets that line the LHC’s 27km-long tunnel must be warmed up, slowly and gently, from -271 Celsius to room temperature. Only then can engineers descend into the tunnel to begin their work.

The machine that last year helped scientists snare the elusive Higgs boson - or a convincing subatomic impostor - faces a two-year shutdown while engineers perform repairs that are needed for the collider to ramp up to its maximum energy in 2015 and beyond. The work will beef up electrical connections in the machine that were identified as weak spots after an incident four years ago that knocked the collider out for more than a year.

The accident happened days after the LHC was first switched on in September 2008, when a short circuit blew a hole in the machine and sprayed six tonnes of helium into the tunnel that houses the collider. Soot was scattered over 700 metres. Since then, the machine has been forced to run at near half its design energy to avoid another disaster.

The particle accelerator, which reveals new physics at work by crashing together the innards of atoms at close to the speed of light, fills a circular, subterranean tunnel a staggering eight kilometres in diameter. Physicists will not sit around idle while the collider is down. There is far more to know about the new Higgs-like particle, and clues to its identity are probably hidden in the piles of raw data the scientists have already gathered, but have had too little time to analyse.

But the LHC was always more than a Higgs hunting machine. There are other mysteries of the universe that it may shed light on. What is the dark matter that clumps invisibly around galaxies? Why are we made of matter, and not antimatter? And why is gravity such a weak force in nature? “We’re only a tiny way into the LHC programme,” says Pippa Wells, a physicist who works on the LHC’s 7000-tonne Atlas detector. “There’s a long way to go yet.”

The hunt for the Higgs boson, which helps explain the masses of other particles, dominated the publicity around the LHC for the simple reason that it was almost certainly there to be found. The lab fast-tracked the search for the particle, but cannot say for sure whether it has found it, or some more exotic entity.

“The headline discovery was just the start,” says Wells. “We need to make more precise measurements, to refine the particle’s mass and understand better how it is produced, and the ways it decays into other particles.” Scientists at Cern expect to have a more complete identikit of the new particle by March, when repair work on the LHC begins in earnest.

By its very nature, dark matter will be tough to find, even when the LHC switches back on at higher energy. The label “dark” refers to the fact that the substance neither emits nor reflects light. The only way dark matter has revealed itself so far is through the pull it exerts on galaxies.

Studies of spinning galaxies show they rotate with such speed that they would tear themselves apart were there not some invisible form of matter holding them together through gravity. There is so much dark matter, it outweighs by five times the normal matter in the observable universe.

The search for dark matter on Earth has failed to reveal what it is made of, but the LHC may be able to make the substance. If the particles that constitute it are light enough, they could be thrown out from the collisions inside the LHC. While they would zip through the collider’s detectors unseen, they would carry energy and momentum with them. Scientists could then infer their creation by totting up the energy and momentum of all the particles produced in a collision, and looking for signs of the missing energy and momentum.

One theory, called supersymmetry, proposes that the universe is made from twice as many varieties of particles as we now understand. The lightest of these particles is a candidate for dark matter.

Wells says that ramping up the energy of the LHC should improve scientists’ chances of creating dark matter: “That would be a huge improvement on where we are today. We would go from knowing what 4 per cent of the universe is, to around 25 per cent.”

Teasing out the constituents of dark matter would be a major prize for particle physicists, and of huge practical value for astronomers and cosmologists who study galaxies.

“Although the big PR focus has been on the Higgs, in fact looking for new particles to provide clues to the big open questions is the main reason for having the LHC,” says Gerry Gilmore, professor of experimental philosophy at the Institute of Astronomy in Cambridge.

“Reality on the large scale is dark matter, with visible matter just froth on the substance. So we focus huge efforts on trying to find out if dark matter is a set of many elementary particles, and hope that some of those particles’ properties will also help to explain some other big questions. So far, astronomy has provided all the information on dark matter, and many of us are working hard to deduce more of its properties. Finding something at the LHC would be wonderful in helping us in understanding that. Of course one needs both the LHC and astronomy. The LHC may find the ingredients nature uses, but astronomy delivers the recipe nature made reality from.”

Another big mystery the Large Hadron Collider may help crack is why we are made of matter instead of antimatter. The big bang should have flung equal amounts of matter and antimatter into the early universe, but today almost all we see is made of matter. What happened at the dawn of time to give matter the upper hand?

The question is central to the work of scientists on the LHCb detector. Collisions inside LHCb produce vast numbers of particles called beauty quarks, and their antimatter counterparts, both of which were common in the aftermath of the big bang. Through studying their behaviour, scientists hope to understand why nature seems to prefer matter over antimatter.

Turning up the energy of the LHC may just give scientists an answer to the question of why gravity is so weak. The force that keeps our feet on the ground may not seem puny, but it certainly is. With just a little effort, we can jump in the air, and so overcome the gravitational pull of the whole six thousand billion billon tonnes of the planet. The other forces of nature are far stronger.

One explanation for gravity’s weakness is that we experience only a fraction of the force, with the rest acting through microscopic, curled up extra dimensions of space. “The gravitational field we see is only the bit in our three dimensions, but actually there are lots of gravitational fields in the fourth dimension, the fifth dimension, and however many more you fancy,” says Andy Parker, professor of high energy physics at Cambridge University. “It’s an elegant idea. The only price you have to pay is that you have to invent these extra dimensions to explain where the gravity has gone.”

The rules of quantum mechanics say that particles behave like waves, and as the LHC ramps up to higher energies the wavelengths of the particles it collides become ever shorter. When the wavelengths of the particles are small enough to match the size of the extra dimensions, they would suddenly feel gravity much more strongly.

“What you’d expect is that as you reach the right energy, you suddenly see inside the extra dimensions, and gravity becomes big and strong instead of feeble and weak,” says Parker. The sudden extra pull of gravity would cause particles to scatter far more inside the machine, giving scientists a clear signal that extra dimensions were real.

Extra dimensions may separate us from realms of space we are completely oblivious to. “There could be a whole universe full of galaxies and stars and civilisations and newspapers that we didn’t know about,” says Parker. “That would be a big deal.”

discoverynews:

Higgs Boson Likely a ‘Boring’ Boson: “The thing with physicists is that they love discovering something unexpected, strange or exotic. This mindset is what makes physics, and indeed all science disciplines, awesome. But in light of the grand announcement of the probable discovery of the elusive Higgs boson in July, it looks like the particle that was discovered is likely a “standard” Higgs boson. As in, it’s a little bit boring.


OK, it’s not really boring. The Higgs boson could never be boring. Just a little, um, antisocial? Find out more.

Will the Real Higgs Please Stand Up? (Infographic)

Physicists working at the Large Hadron Collider (LHC) in Switzerland have observed evidence of a new subatomic particle. Further research will try to determine if it is the elusive Higgs boson, thought to be responsible for giving matter its property of mass.

In the Standard Model of physics, matter is made up of small particles called fermions (including quarks and leptons). Forces such as electromagnetism are carried by bosons.

Physicists use electromagnetic fields to whip beams of protons around and around, accelerating them to nearly the speed of light. This gives the protons enormous kinetic energy. Finally the beams are allowed to intersect, and where protons collide, their energy is released. New particles – some of them very short-lived – are formed from this energy.

As Albert Einstein discovered, mass can be defined as a quantity of energy. Subatomic particle masses are given as amounts of electron volts (the energy of a single electron accelerated by a potential difference of one volt). The newly discovered particle - possibly the Higgs boson – is found to have a mass of about 125 billion electron volts. Other particles, such as photons, have no mass at all.

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sevenisles:

Leonardo da Vinci-esque Large Hadron Collider by Dr. Sergio Cittolin.

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skepttv:

Ri Discourse: Jon Butterworth - Electroweak Symmetry Breaking and the LHC

Professor Jon Butterworth, member of the High Energy Physics group on the Atlas experiment, provides an overview of his work at the Large Hadron Collider (LHC).

This Ri Discourse took place on Friday 3 February 2012.

It cannot be understated how important (and how cool) physical symmetries and postulates concerning these are.

(via skeptv)

Is the Higgs boson real?

Imaged Above: A collision event recorded by Atlas at the LHC. Bloggers report rumours that evidence of the Higgs boson will be announced next Tuesday. Photograph: Cern/PA

A couple of blogs, including viXra and Peter Woit’s Not Even Wrong, have now posted rumours that the Atlas and CMS teams see Higgs-like signals around 125GeV, though they say the evidence is not robust enough to claim an official discovery.

Could a Higgs Boson Announcement Be Imminent From the LHC?

Physicists at the Large Hadron Collider could be getting an early Christmas present: the Higgs boson. According to the latest rumors, scientists at the LHC are seeing a signal that could correspond to a Higgs particle with a mass of 125 GeV (a proton is slightly less than 1 GeV).

Public talks are scheduled to discuss the latest results from ATLAS and CMS, two of the main LHC experiments, on Dec. 13. This follows one day after a closed-door CERN council meeting where officials will get a short preview of the findings, whatever they may be.

“Chances are high (but not strictly 100%) that the talks will either announce a (de facto or de iure) discovery or some far-reaching exclusion that will be really qualitative and unexpected,” wrote theoretical physicist Lubos Motl on his blog.

LHC May Have Found Crack in Modern Physics

In late 2008, a few onlookers believed that the Large Hadron Collider (LHC) would bring the end of the world. Three years later, our planet remains intact, but the European particle smasher may have made its first crack in modern physics.

If this crack turns out to be real, it might help explain an enduring mystery of the universe: why there’s lots of normal matter, but hardly any of the opposite—antimatter. “If it holds up, it’s exciting,” says particle physicist Robert Roser of the Fermi National Accelerator Laboratory in Batavia, Illinois.

To understand why physicists are excited, look around: We’re surrounded by stuff. That might seem obvious, but scientists have long wondered why there’s anything at all. Accepted theories suggest that the big bang should have produced equal amounts of matter and antimatter, which would have soon annihilated each other. Clearly, the balance tipped in favor of normal matter, allowing the creation of everything we see today—but how, no one’s sure.

More On: LHC May Have Found a Crack in Modern Physics

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No Higgs? No Problem.. For Now

The world’s most-wanted particle continues to elude the world’s most powerful particle accelerator. A sign that the elusive Higgs boson doesn’t exist? Not so fast. For now, there are good reasons to assume the Higgs is just hiding.

“It’s never too early to think about it, but it is too early to worry,” says Nobel prize-winner Frank Wilczek of the Massachusetts Institute of Technology.

The still-hypothetical Higgs boson is thought to endow all other particles with mass. Confirming its existence would complete the standard model of physics, the leading theory for how particles and forces interact. Finding the Higgs and pinning down its mass, or ruling out its existence and paving the way for new models, is one of the goals of the Large Hadron Collider at CERN near Geneva, Switzerland.

Since it started smashing protons together in 2009, the LHC has steadily collected data that help rule out various masses for the Higgs from a range of possibilities allowed by the standard model. Combined with earlier results from other accelerators, the latest LHC limits, announced on 22 August at the Lepton-Photon conference in Mumbai, India, mean the Higgs is now restricted to having a mass of between 115 and 145 gigaelectronvolts (GeV), or 122 to 154 times the mass of a proton (mass and energy can be treated interchangeably for particles).

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