Tag archives: particle accelerator
By Matin Durrani and Tushna Commissariat
If you’re in the tiny minority of people whose job title says “particle physicist”, chances are you’ll have been to CERN at least once in your career to help build a detector, analyse some collision data or muse in the cafeteria over supersymmetry (or the apparent lack of it so far). But for the rest of the world, going to the Geneva lab is simply not on the agenda, which is one reason why the Science Museum in London has this week unveiled a big new exhibition devoted to CERN’s Large Hadron Collider. Entitled simply Collider, the exhibition “blends theatre, video and sound art with real artefacts from CERN” that will, say organizers, “recreate a visit to the famous particle-physics laboratory”.
By Tushna Commissariat
In June we reported that physicists working on the BESIII experiment in Beijing and the Belle experiment in Tsukuba, Japan found evidence for a new “charged charmonium” called Zc(3900). A “charged charmonium” is a particle that is made of four quarks – something that had never been seen before. Since that discovery, the BESIII collaboration says it has made “a rapid string of related discoveries” of four-quark particles. “While quarks have long been known to bind together in groups of twos or threes, these new results seem to be quickly opening the door to a previously elusive type of four-quark matter,” says Frederick Harris, spokesman for the BESIII experiment. “The unique data sample collected by the BESIII collaboration has continued to yield a stream of clues about the nature of multi-quark objects.”
By Hamish Johnston
There is an interesting paper in Physical Review Letters this week with the mouthful of a title: “Enhancement of electron energy to the multi-GeV regime by a dual-stage laser-wakefield accelerator pumped by petawatt laser pulses“. This piqued my interest because I recently wrote an article for the 25th anniversary issue of Physics World that looks at how laser acceleration of protons and other hadrons could make certain cancer therapies more accessible.
By Michael Banks
All eyes will be on Stockholm next week as the 2013 Nobel Prize for Physics is announced. One of the frontrunners for the prize in the minds of the Royal Swedish Academy of Sciences will surely be the discovery last year of the Higgs boson at CERN’s Large Hadron Collider (LHC).
But the LHC story is far from over and in the latest Physics World focus issue on “big science” find out how the LHC will hunt for new particles beyond the Higgs boson once the collider restarts in 2015 following an 18-month repair and upgrade programme at the Geneva-based lab.
All full members of the Institute of Physics will receive a print edition of the focus issue along with their copy of the October issue of Physics World, but everyone can access a free digital edition. The focus issue also looks at how particle physicists are already thinking about what could come after the LHC, with bold plans for a 80–100 km proton–proton collider. There are even plans for a collider based on lasers, with an international team looking at creating an array of “fibre lasers” to be used as a future “Higgs factory”.
By James Dacey
My colleague, Hamish Johnston, has just returned from a trip to CERN, where he was granted access to the insides of the Large Hadron Colider (LHC), which is currently being upgraded. He has shared some great photos from his trip on the Physics World Facebook page, including some snaps of the interior of the detector experiments.
By Hamish Johnston
The physicist and best-selling author Frank Close has joined forces with Michael Marten – founder of the Science Photo Library (SPL) – and CERN Courier editor Christine Sutton to create a new app about particle physics. Called The Particles, the app is billed as an introduction to the Standard Model and is aimed at a wide audience that includes professional physicists, students and even amateur enthusiasts.
By Tushna Commissariat
Looks like the Large Hadron Collider (LHC) at the CERN particle physics lab had an interesting few days last week, just before everybody left for Easter, and the Internet is now abuzz with rumours of an impending discovery.
But before we get into any of the highly interesting and debatable stuff, let’s look at one thing that has definitely happened at the LHC.
Around midnight on Friday 22 April, the LHC set a new world record for beam intensity when it collided beams with a luminosity of 4.67 × 1032 cm–2s–1. This was significantly more than the previous luminosity record of 4.024 × 1032 cm–2s–1 held by the US Fermi National Accelerator Laboratory’s Tevatron collider in 2010.
This new beam intensity was achieved after two weeks of planning and readying the collider. The machine is now moving into a phase of continuous physics scheduled to last until the end of the year when, after a short technical stop, the machine will resume running for 2012.
“Beam intensity is key to the success of the LHC, so this is a very important step,” said CERN director Rolf-Dieter Heuer in a statement. “Higher intensity means more data, and more data means greater discovery potential.”
But didn’t I read all about some record being broken by the LHC last year, you ask? Yes, but that was the LHC accelerating its proton beams to 3.5 TeV each, leading to later collisions at 7 TeV. Now it is the beam intensity or the “luminosity” that is record breaking. Luminosity gives a measure of how many collisions are happening in a particle accelerator. So the higher the luminosity, the more particles are likely to collide which is necessary while looking for rare particles like the infamous Higgs boson.
“There’s a great deal of excitement at CERN today,” said CERN’s director for research and scientific computing, Sergio Bertolucci, “and a tangible feeling that we’re on the threshold of new discovery.”
Well, it looks like Bertolucci spoke a tad too soon, as on the same day a leaked memo posted by an anonymous commenter on mathematician Peter Woit’s blog, claimed that certain researchers at the ATLAS experiment at CERN had seen firm evidence for the Higgs particle in recent data.
The memo, though not official by any means, was authored by four ATLAS members who claimed to have seen an excess number of photons produced at energy of 115 GeV that could be caused by the decay of the Higgs particle into photons.
Surprisingly, only a few websites and blogs mentioned the news for the first day or so, before slowly more people seemed to notice this juicy story of physics, Higgs and betrayal!
On 25 April, Nature reported on its blog, an official statement from ATLAS spokeswoman Fabiola Gianotti. Gianotti said “Only official ATLAS results, i.e. results that have undergone all the necessary scientific checks by the collaboration, should be taken seriously.” She went on to say that signals of the kind reported in the memo show up often during data analysis and are later falsified after more detailed scrutiny.
But the damage had already been done as physicists and others began to comment on the legitimacy of the claim made in the memo and the ethics of such an internal memo being posted and talked about online.
As people began to look deeper into the memo, interesting facts began to creep up.
Tommaso Dorigo, from the University of Padova in Italy wrote an initial post on his blog A Quantum Diaries Survivor that turned into a debate and eventually a bet! His post was sceptical from the start and he gave his reasons for why he was sure it as nothing more than a blip in the data, then went on to explain in more detail what other data already exists.
After that, a regular reader of his blog pointed out that the authors of the ATLAS study are actually physicists from Wisconsin, and include a Professor Wu, “who was among those less happy of the decommissioning of LEP [the Large Electron-Positron Collider] at the time when they were claiming a possible Higgs signal at 115 GeV. So maybe these guys have been looking for some confirmation of the 115 GeV Higgs all along”.
Woit too was quick to distance himself from the memo saying that “it should be made clear that, while members of ATLAS work here at Columbia, I have no connection at all to them, and they had nothing to do with this. The source of the abstract posted here anonymously as a comment is completely unknown to me.”
As more people debated and commented over the memo, Dorigo came back to say that he would bet anyone who “has a name and a reputation in particle physics (this is a necessary specification, because I need to be sure that the person taking the bet will honour it) that the signal is not due to Higgs boson decays” and then updated that comment by saying that if he is wrong he would pay $1000 but that if he is right he would be given only $500.
Meanwhile, Channel 4 conducted an interview with Jon Butterworth, a particle physics professor at University College London, who also works at ATLAS. He went on to say the same thing; that nothing would be definitive until it was scrutinized by CERN officially (look above).
So at the end of the day, it looks like the world is going to have to wait a while longer before Higgs boson gets its official post in the Standard Model hall of fame.