After several years of nail-biting delays and breakdowns, the Large Hadron Collider, one of the few science experiments to become a household name, got underway in March of 2010. The search for the Higgs boson, the elusive “God particle” that would resolve several problems in the Standard Model of particle physics, was front-page news.
But in the last 18 months, as the LHC has scanned through various energies, the Higgs has not showed itself. And at a conference in Mumbai on August 22, CERN scientists revealed news that set the physics community humming: in the energies so far explored, there’s a 95% probability that the Higgs doesn’t exist. Amir Azcel, writing in a guest blog at Scientific American, explains these numbers, considers the tumult in particle physics that will occur should the Higgs prove no more than theoretical, and asks whether Stephen Hawking has just won his infamous bet against the Higgs:
A few years ago, celebrated British physicist Stephen Hawking was widely reported in the press to have placed a provocative public bet that the LHC (along with all particle accelerators that preceded it) would never find the Higgs boson, the so-called “God particle” believed responsible for having imbued massive particles with their mass when the universe was very young.
Read more at Scientific American.
Image courtesy of CERN
Since 1983, the Tevatron particle accelerator at Fermilab outside Chicago has been faithfully smashing particles and probing deeper into the mysteries of physics. But its time is nearly at an end.
The Large Hadron Collider—that big European underground ring you might have heard of—surpassed Tevatron in size and energy. The American collider’s operators had hoped to extend its life a few more years, especially with LHC still getting up to speed. But the money just wasn’t there, and so the announcement came yesterday that Tevatron would shut down in September.
From John Conway at DISCOVER blog Cosmic Variance:
In the fall, the Department of Energy’s High Energy Physics Advisory Panel recommended that the Tevatron be funded to run for three years beyond the planned end in September of 2011, largely in order to provide additional information in the search for the Higgs boson. … But in a letter to day to the chair of HEPAP, the head of the Office of Science at the Department of Energy, William Brinkman, wrote that “Unfortunately, the current budgetary climate is very challenging, and additional funding has not been identified. Therefore…operation of the Tevatron will end in FY2011, as originally scheduled.”
Conway’s lengthy eulogy for a particle accelerator is a great read, including plenty of the history of the rivalry between American physicists and the CERN physicists in Europe building their own huge smashers, leading up to the LHC.
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Image: Wikimedia Commons
You know those black holes the Large Hadron Collider was going to make and kill us all? Well, not only are we still here, but the LHC doesn’t seem to be making black holes at all—their decay signature is markedly absent from the data collected so far.
While that is good for those of us who want to keep living (we jest—the hypothetical micro black holes posed no danger), it’s also helping physicists make up their minds about how many dimensions there are in our universe. The lack of black holes at the LHC nullifies some of the wackier versions of string theory which depend on multiple dimensions.
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Now that the Large Hadron Collider is smashing lead, the discoveries are coming fast and furious.
Earlier this month CERN’s smashing machine switched from sending protons zinging around its ring to sending heavy lead ions at relativistic speeds. Those energetic collisions, the physicists now say, have allowed them to use the LHC’s ALICE experiment to glimpse quark-gluon plasma, the “primordial soup” present just after the Big Bang.
During this time, the Universe would have been so hot and energetic that the particles making up the elements we know today were unable to form, leaving the constituents to float “free” as a primordial soup. Quarks and gluons were only able to condense into larger particles when universal energy conditions were low enough. Hadrons (i.e. particles made from quarks; including baryons like neutrons and protons) were only allowed to form 10-6 seconds after the Big Bang. [Discovery News]
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If there was a race to see which Large Hadron Collider experiment would provide the first surprise, and the first giddy claims of possible “new physics,” it appears the Compact Muon Solenoid (CMS) has won. CERN scientists announced this week that the most high-energy proton smash-ups produced an weird effect: particles created in the collision were somehow linked together and flew off in an unexpected direction.
In the new experiment, the CMS team took data on the charged particles produced in hundreds of thousands of collisions. The team observed the angles the particles’ paths took with respect to each other, and calculated something called a “correlation function” to determine how intimately the particles are linked after they separate. The plot of the data ends up looking like a topographical map of a mountain surrounded by lowlands and a long ridge behind it (see below). [Wired.com]
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As a younger stronger particle smasher, the Large Hadron Collider can turn even baby steps into new records. Over this past weekend, the LHC beat another personal best–colliding its most protons yet at 10,000 particle collisions per second (about double its earlier rate). Physicists believe this is a crucial step on the collider’s hunt for new physics.
In November of 2009, the LHC collided its first protons as it started its quest to find the suspected mass-giving particle known as the Higgs Boson. The collider is still running at half of its designed maximum energy, but after this weekend, the number of particles per bunch traveling in the ring is just what physicists had planned. This is essential, says CERN physicist John Ellis:
“Protons are complicated particles, they’ve got quarks, [and other small particles], and colliding them is like colliding two garbage cans and watching carrots come out…. The more collisions we get, the closer we get to supersymmetry, dark matter, the Higgs boson and other types of new physics.” [BBC]
Here are some basics:
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As opposed to simply energy, the universe is also made of stuff. Not a whole lot of stuff, mind you, at least if you compare the matter we experience to the vast emptiness of space or the preponderance of dark matter. But enough.
The continued prevalence of matter has long been one of my favorite attributes of the universe, given that it allows for the existence of galaxies, and Guinness. However, it’s the source of confusion to physicists. In short, there should have been equal amounts of matter and antimatter present at the creation of the universe, which doesn’t make sense:
If matter and antimatter had come out even in those first moments, they would have instantly destroyed each other, leaving nothing but energy behind [TIME].
But they didn’t; as sure as I’m sitting here, matter won out. And this week, at the Tevatron particle smasher in Illinois, a new clue to the problem has emerged. In a study for Physical Review D, physicist Dmitri Denisov and his colleagues explain that in long-running proton-antiproton collisions (nearly 8 years of them), they saw a slight favoritism toward normal matter in a particular place:
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The smashing has started. Now the science can commence.
Last week we reported that the Large Hadron Collider’s operators at CERN targeted today to attempt the highest energy particle collisions ever. And to show the world that yes, in fact, the LHC can meet a deadline, today they slammed together the two proton beams, each carrying 3.5 trillion electron volts, to produce 7 TeV collisions. As the first data from the impacts were announced, physicists who had gathered at CERN applauded, jumped up and down, and clutched laptops displaying images of the collisions to their chests as if the computers were newborn babes [National Geographic].
While the physicists enjoy their moment of euphoria, they caution that it will be some time before the LHC’s collisions translate into new data that could reveal deeper secrets of the universe. “Major discoveries will happen only when we are able to collect billions of events and identify among them the very rare events that could present a new state of matter or new particles,” said Guido Tonelli, a spokesman for the CMS detector at the LHC. “This is not going to happen tomorrow. It will require months and years of patient work” [BBC News]. This round of collisions should last a year and a half or so. After a planned shutdown, the physicists plant to crank up the collider to its full power of 14 TeV.
For more about the long road to now and the future of LHC physics, follow DISCOVER blog Cosmic Variance.
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Image: CERN
Are you ready for some subatomic smash-ups? Good, because the Large Hadron Collider is about ready to get serious. Everyone’s favorite long-delayed particle collider fended off rumors of its demise earlier in the month, and last week it reached a new energy record for its circulating proton beams: 3.5 trillion electron volts (TeV). That marked the highest particle energy ever accomplished by humans. A week from today, March 30, the LHC will start trying to smash those two beams together for the highest energy collisions yet.
“Just lining the beams up is a challenge in itself: it’s a bit like firing needles across the Atlantic and getting them to collide half way,” said CERN’s Director for Accelerators and Technology, Steve Myers [AFP]. So while the CERN scientists will fire up the machine and make their first attempt on March 30, they acknowledge that it could take a few hours or days to get everything set and start gathering data.
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It sounded again today like the Large Hadron Collider—previously the victim of technical failure, hackers, and avian sabateurs—was cursed. The BBC reported that the world’s largest particle collider would have to shut down at the end of 2011, possibly for an entire year, to address its mechanical problems, according to LHC director Steven Myers. The report states that the faults will delay the machine reaching its full potential for two years [BBC News].
Just one problem, though: While the information came out as another “LHC is broken” news break, Myers actually put forth the intended schedule more than a month ago. The LHC team announced that it would actually extend the physics run through until December 2011, before shutting the accelerator down for a year. The only real delay here has been to the reporting of the story [The Times]. Brian Cox, one of the project scientists, spent the morning tweeting up a storm in protest to the news handling of what he says is just a scheduled shutdown. (A typical tweet reads: “For the very last time – the #lhc story is a pile of merde, as we say at CERN. Scheduled maintenance stops are not bloody news!”)
The LHC will keep running until late next year at 7 trillion electron volts (TeV), as planned. The engineers will go in after that to carry out the planned maintenance on systems in the tunnel that have proven problematic so far; their improvements should allow the LHC to approach what was the goal from the start, doing physics at 14 TeV. In any case, the machine’s upcoming resting time isn’t an emergency shutdown. Particle accelerators are regularly shut down for re-engineering. They are huge, complex instruments, and it’s just impossible to run them full-time like a domestic boiler [The Times].
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Image: Claudia Marcelloni / CERN
If you were following Cosmic Variance yesterday, you saw its live blogging of one of the most anticipated recent announcements in physics: the team from Cryogenic Dark Matter Search (CDMS) telling the world whether a Minnesota detector spotted evidence of dark matter. The answer? Maybe (pdf).
CDMS scientists use super-cooled detectors made of germanium and silicon to search for weakly interacting massive particles (WIMPs), one of the leading suspects for what could make up dark matter. The detector is deep underground in the Soudan mine in Minnesota, which scientists also use to hunt for neutrinos. WIMPs streaming in from space would very rarely jostle the germanium nuclei, some 800 meters underground in the Soudan mine, generating a tiny amount of heat and slightly altering the charge on the detectors in a characteristic pattern [Science News].
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Long hyped as the largest science experiment ever built, the Large Hadron Collider now has a world record for doing something: accelerating particles with more energy than any accelerator ever has.
On Sunday evening, at 6:44 p.m. eastern time in the United States, engineers at the Switzerland-based accelerator increased the energy of this “pilot beam”, reaching 1.18 trillion electron volts…. The previous record of 0.98 trillion electron volts has been held by the Tevatron accelerator since 2001 [BBC News].
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Neither baguette-dropping birds nor future sabatoge schemes could stop the LHC this week. And no, the world was not sucked into a black hole, as you may have noticed. Shortly after flinging the first proton beams around the collider, the first particle collisons were recorded. After 14 months of repairs, Cern engineers have got the Large Hadron Collider to smash particles together far sooner than anyone dared hope. For the time being the collisions are low energy, around 450 billion electronvolts per beam, which is around half the energy of what remains, for now, the world’s most powerful particle collider: the Tevatron at Fermilab on the outskirts of Chicago [Guardian]. The LHC’s Atlas detector snapped an image of two counter-rotating proton beams that collided head-on.
Scientists are hopeful that this first collison will lead to smoother operations in the future, but they are being cautious considering the LHC’s laundry list of past failures. The European collider is intended to eventually collide proton beams at an energy of seven trillion electron volts. The first experiments in the LHC are scheduled to take place in early 2010, when researchers will smash subatomic particles into each other at high speeds in order to break them down and allow the discovery of smaller, more fundamental particles [CBC News]. CERN has an image gallery of the LHC’s first run here.
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Image: CERN
Hackers. Leaking liquid helium caused by a faulty connection. International ridicule. And to top it all off, aerial attack by a wayward baguette. Yes, it’s safe to say that things haven’t gone according to plan at the Large Hadron Collider in the last 14 months, but the world’s largest particle smasher is finally—finally!—back online after its Friday restart, with proton beams circulating through this huge underground ring.
The first time protons circled the collider, on Sept. 10, 2008, the event was celebrated with Champagne and midnight pajama parties around the world. But the festivities were cut short a few days later when an electrical connection between a pair of the collider’s giant superconducting electromagnets vaporized [The New York Times].
The initial enthusiasm, it seems, was rather premature—scientists analysis of the failed connection revealed many more that probably couldn’t handle the strain of the energy needed to re-create conditions similar to the Big Bang. During 14 months of repairs dozens of giant superconducting magnets that accelerate particles at the speed of light had to be replaced [BBC News].
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Particle physicists have ruled out one of the possible remaining hiding places of the Higgs boson, bringing them one step closer to finding the slippery subatomic particle–or, conceivably, to ruling out its existence.
Physicists believe that the Higgs particle interacts with some other particles, like the W and Z bosons, to give them mass. The standard quip about the Higgs is that it is the “God Particle” — it is everywhere but remains frustratingly elusive. Confirming the Higgs would fill a huge gap in the so-called Standard Model, the theory that summarizes our present knowledge of particles [AFP].
The new results, from the Tevatron particle accelerator at the Fermi National Accelerator Laboratory, narrow down the range of masses where the Higgs boson may be found. Physicist Craig Blocker explains that particle accelerators smash particles together and then sift through the debris produced, looking for particles with certain masses. Previous collider experiments had placed a lower bound of 114 giga-electron volts (GeV), a measure that can be used for particle mass, on the Higgs, and theoretical calculations require it to be less than 185 GeV. The new Fermilab results, from its Tevatron collider, rule out a Higgs mass between 160 and 170 GeV…. “If the Higgs had a mass in this fairly narrow range” of 160 to 170 GeV, he says, “we should have seen it, we had a good chance to see it” [Scientific American].
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