Posts tagged: large hadron collider
From the Guardian a couple weeks ago:
Scientists working at the Large Hadron Collider have found no evidence that the new particle discovered earlier this year is anything but the simplest – and most boring – variety of Higgs boson.
Staff at Cern, the particle physics lab near Geneva, celebrated in July after they found what looked like the elusive boson amid the debris of scores of high-energy collisions inside the huge machine.
At the time, preliminary results from the two main experiments, Atlas and CMS, hinted that the particle might be something more exciting than the singular beast originally described in equations nearly 50 years ago. A more exotic Higgs could pave the way to a profound new understanding of nature.
But fresh data released by both teams at a conference in Kyoto today show that – so far at least – there is nothing peculiar about the particle’s behaviour. The results do not completely rule out a more exotic Higgs particle, though. Some versions would look so much like the so-called Standard Model Higgs boson they could take years to identify.
As you’ve likely heard, both the ATLAS and CMS teams at the Large Hadron Collider believe they’ve found the Higgs Boson:
Crucially, both teams’ findings appear exceptionally robust. In physics terms, evidence for a new particle requires a “3-sigma” measurement, corresponding to a 1-in-740 chance that a random fluke could explain the observations, and a claim of discovery requires a 5-sigma effect, or a 1-in–3.5 million shot that the observations are due to chance. In December representatives of the two experiments had announced what one called “intriguing, tantalizing hints” of something brewing in the collider data. But those hints fell short of the 3-sigma level. The new ATLAS finding met not just that level of significance but cleared the gold standard 5-sigma threshold, and CMS very nearly did as well, with a 4.9-sigma finding. […]
The newfound particle fits the bill for the Higgs boson, but the researchers cautioned that more work is needed to compare the properties of the particle to those predicted for the Higgs. After all, the LHC’s detectors cannot identify the Higgs directly. The LHC accelerates protons to unprecedented energies of four trillion electron-volts (4 TeV) before colliding a clockwise-traveling proton beam with a counterclockwise beam. From the smash-up new particles emerge, some of them existing for just an instant before decaying to other particles.
The Chi_b (3P) is a more excited state of Chi particles already seen in previous collision experiments, explained Prof Roger Jones, who works on the Atlas detector at the LHC.
“The new particle is made up of a ‘beauty quark’ and a ‘beauty anti-quark’, which are then bound together,” he told BBC News.
“People have thought this more excited state should exist for years but nobody has managed to see it until now.
“It’s also interesting for what it tells us about the forces that hold the quark and the anti-quark together - the strong nuclear force. And that’s the same force that holds, for instance, the atomic nucleus together with its protons and the neutrons.”
Jon Butterworth, a member of the High Energy Physics group on the ATLAS experiment at CERN’s Large Hadron Collider confirms that the group thinks it may have found the higgs boson particle. He writes on his blog at The Guardian:
So, it is not a hoax. But the rumours are based on an analysis which has to pass many levels of scientific scrutiny before I get very excited by it. It could fail at any stage. If it passes, it will be released by ATLAS, and will then be submitted to a journal. For comparison, journal submission acceptance is the stage the CDF bump has got to, and that is far from established yet as a real new physics effect.
The thing is, CERN is an exciting place right now. New data are coming in as I write. There are lots of levels of collaboration and competition. Retaining a detached scientific approach is sometimes difficult. And if we can’t always keep clear heads ourselves, it’s not surprising people outside get excited too. This is why we have internal scrutiny, separate teams working on the same analysis, external peer review, repeat experiments, and so on…
So don’t go tearing up your particle physics text books just yet. But please stay tuned for when we really do have something to say! These are indeed interesting times.
The results continue to pour out of the LHC’s first production run. This week, the folks behind the CMS detector have announced the submission of a paper to Physics Letters that describes a test of some forms of string theory. If this form of the theory were right, the LHC should have been able to produce small black holes that would instantly decay (and not, as some had feared, devour the Earth). But a look at the data obtained by CMS shows that a signature of the black holes’ decay is notably absent. […]
Contrary to some reports, this result doesn’t mean the death of string theory, only the particular flavor that predicted black holes at these energies. Eliminating some models is a critical process of narrowing down what’s possible, but most theoretical constructs have a range of possible models, and string theory is no different. In fact, it’s entirely possible that the ADD model was generated simply because physicists were looking for something they could possibly test in the LHC.
Russia is building its own particle accelerator:
The project, nicknamed NIKA and due to be launched in 2016, may reproduce “Big Bang” conditions that gave birth to our Universe and provide ideas of how the Solar system formed.
While Geneva is seeking to discover the smallest known particles, NIKA scientists aim to study the process of these particles’ appearance several billion years ago, which will probably help the mankind unlock some riddles of the Universe.