The Large Hadron Collider, on the Franco-Swiss border near Geneva. Photo: Getty Images
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The Large Hadron Collider has made another exciting quantum discovery

Scientists working on one of the four experiments at the LHC have gathered enough evidence to confirm the existence of a four-quark particle.

Since the spectacular discovery of the Higgs boson in 2012, physicists at the Large Hadron Collider (LHC), the gigantic particle accelerator outside Geneva, have suffered a bit of a drought when it comes to finding new particles. In a welcome relief, the LHCb collaboration, who run one of four large experiments at the LHC, have announced one of the most genuinely exciting observations to come out of the 27km super-collider so far – an exotic particle that cannot be explained by current theories.

In the early 1930s physicists had a clean picture of the subatomic particles that make up our world. Every known atom has a tiny nucleus at its heart surrounded by a cloud of electrons, and each nucleus was made out of varying numbers of protons and neutrons. However, as the decades wore on a number of new, and somewhat unwelcome, particles were discovered, at first in detectors studying particles from outer space and later in particle-collider experiments.

By the 1950s, dozens of apparently elementary particles had been discovered, causing frustration among physicists who often brandish an inability to memorise a list of facts as a badge of honour. The famous physicist Enrico Fermi perhaps best expressed the mood of his colleagues in an infamous remark:

Young man, if I could remember the names of these particles, I would have been a botanist.”

Help came in the 1950s when physicists came up with a new model that explained most of these particles as being made up of a small number of truly elementary particles. Borrowing a line from James Joyce’s Finnegans Wake (a book that is even harder to understand than quantum field theory), Murray Gell-Mann dubbed these new particles “quarks”.

By the late 1960s the existence of quarks had been verified experimentally. We now know that there are six in total – the up, down, strange, charm, bottom and top quarks, along with six antiquarks (their anti-matter copies).

The quark model neatly explained all these peculiar particles. Protons, neutrons and many others besides are made of three quarks, belonging to a family known as baryons. Alternatively, a quark and an antiquark can pair up to form a meson.

Since then the quark model has been extremely successful, and is now a cornerstone of our understanding of particle physics. It was only at the turn of the millennium that some strange results started to suggest that the model might be incomplete. Until 2003 quarks had only been seen in twos or threes, but then a number of particles that looked like combinations of four quarks started to reveal themselves.

In 2008 the Belle Collaboration in Japan reported the observation of a new exotic particle – the unfortunately drably named Z(4430) (where for its negative charge). This has a mass that places it in a dense forest of charmonium states – particles that are made up of a charm quark and a charm antiquark. Crucially though, the Z is electrically charged whereas all charmonium states must be neutral, clearly marking it out as something unusual.

After a careful analysis of data from 25,000 decays of mesons resulting from more than 180 trillion collisions at the LHC in 2011 and 2012, the new announcement confirms the existence of Z(4430) with extremely high confidence. The particle was observed with an overwhelming significance of 13.9 sigma, well above the usual 5 sigma threshold required to declare a discovery. LHCb also went further than Belle by measuring the spin and parity of Z(4430), two quantum-mechanical properties that give a firm handle on the internal makeup of the particle.

The observation by LHCb is important because few physicists will take a result seriously until it has been seen by two independent experiments. This is why hundreds of millions of Euros were spent building two large detectors at the LHC. The observation of the Higgs boson by two independent teams, ATLAS and CMS, was what really convinced the scientific community that the particle was real.

This result is the clearest evidence yet of the existence of a tetraquark – a four-quark state, with the LHCb analysis suggesting that Z(4430) is most likely to be made of a charm, anti-charm, down and anti-up quark. Theorists are now able to add a whole new type of particle to the quark model and begin the hard work of trying to understand exactly how these four quarks are bound together.

Meanwhile, physicists working at the LHC experiments will continue to explore unmapped regions of the subatomic world, with the hope of turning up more members of this exotic new family. Now that we know that at least one is out there, it is very unlikely that Z(4430) is alone.The Conversation

Harry Cliff is affiliated with the University of Cambridge, CERN, the LHCb experiment.

This article was originally published on The Conversation. Read the original article.

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Fark.com’s censorship story is a striking insight into Google’s unchecked power

The founder of the community-driven website claims its advertising revenue was cut off for five weeks.

When Microsoft launched its new search engine Bing in 2009, it wasted no time in trying to get the word out. By striking a deal with the producers of the American teen drama Gossip Girl, it made a range of beautiful characters utter the words “Bing it!” in a way that fell clumsily on the audience’s ears. By the early Noughties, “search it” had already been universally replaced by the words “Google it”, a phrase that had become so ubiquitous that anything else sounded odd.

A screenshot from Gossip Girl, via ildarabbit.wordpress.com

Like Hoover and Tupperware before it, Google’s brand name has now become a generic term.

Yet only recently have concerns about Google’s pervasiveness received mainstream attention. Last month, The Observer ran a story about Google’s auto-fill pulling up the suggested question of “Are Jews evil?” and giving hate speech prominence in the first page of search results. Within a day, Google had altered the autocomplete results.

Though the company’s response may seem promising, it is important to remember that Google isn’t just a search engine (Google’s parent company, Alphabet, has too many subdivisions to mention). Google AdSense is an online advertising service that allows many websites to profit from hosting advertisements on its pages, including the New Statesman itself. Yesterday, Drew Curtis, the founder of the internet news aggregator Fark.com, shared a story about his experiences with the service.

Under the headline “Google farked us over”, Curtis wrote:

“This past October we suffered a huge financial hit because Google mistakenly identified an image that was posted in our comments section over half a decade ago as an underage adult image – which is a felony by the way. Our ads were turned off for almost five weeks – completely and totally their mistake – and they refuse to make it right.”

The image was of a fully-clothed actress who was an adult at the time, yet Curtis claims Google flagged it because of “a small pedo bear logo” – a meme used to mock paedophiles online. More troubling than Google’s decision, however, is the difficulty that Curtis had contacting the company and resolving the issue, a process which he claims took five weeks. He wrote:

“During this five week period where our ads were shut off, every single interaction with Google Policy took between one to five days. One example: Google Policy told us they shut our ads off due to an image. Without telling us where it was. When I immediately responded and asked them where it was, the response took three more days.”

Curtis claims that other sites have had these issues but are too afraid of Google to speak out publicly. A Google spokesperson says: "We constantly review publishers for compliance with our AdSense policies and take action in the event of violations. If publishers want to appeal or learn more about actions taken with respect to their account, they can find information at the help centre here.”

Fark.com has lost revenue because of Google’s decision, according to Curtis, who sent out a plea for new subscribers to help it “get back on track”. It is easy to see how a smaller website could have been ruined in a similar scenario.


The offending image, via Fark

Google’s decision was not sinister, and it is obviously important that it tackles things that violate its policies. The lack of transparency around such decisions, and the difficulty getting in touch with Google, are troubling, however, as much of the media relies on the AdSense service to exist.

Even if Google doesn’t actively abuse this power, it is disturbing that it has the means by which to strangle any online publication, and worrying that smaller organisations can have problems getting in contact with it to solve any issues. In light of the recent news about Google's search results, the picture painted becomes more even troubling.

Update, 13/01/17:

Another Google spokesperson got in touch to provide the following statement: “We have an existing set of publisher policies that govern where Google ads may be placed in order to protect users from harmful, misleading or inappropriate content.  We enforce these policies vigorously, and taking action may include suspending ads on their site. Publishers can appeal these actions.”

Amelia Tait is a technology and digital culture writer at the New Statesman.