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.

@Simon_Cullen via Twitter
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All 27 things wrong with today’s Daily Mail front cover

Where do I even start?

Hello. Have you seen today’s Daily Mail cover? It is wrong. Very wrong. So wrong that if you have seen today’s Daily Mail cover, you no doubt immediately turned to the person nearest to you to ask: “Have you seen today’s Daily Mail cover? It is wrong.”

But just how wrong is the wrong Mail cover? Let me count the ways.

  1. Why does it say “web” and not “the web”?
  2. Perhaps they were looking on a spider’s web and to be honest that makes more sense because
  3. How does it take TWO MINUTES to use a search engine to find out that cars can kill people?
  4. Are the Mail team like your Year 8 Geography teacher, stuck in an infinite loop of typing G o o g l e . c o m into the Google search bar, the search bar that they could’ve just used to search for the thing they want?
  5. And then when they finally typed G o o g l e . c o m, did they laboriously fill in their search term and drag the cursor to click “Search” instead of just pressing Enter?
  6. The Daily Mail just won Newspaper of the Year at the Press Awards
  7. Are the Daily Mail – Newspaper of the Year – saying that Google should be banned?
  8. If so, do they think we should ban libraries, primary education, and the written word?
  9. Sadly, we know the answer to this
  10. Google – the greatest source of information in the history of human civilisation – is not a friend to terrorists; it is a friend to teachers, doctors, students, journalists, and teenage girls who aren’t quite sure how to put a tampon in for the first time
  11. Upon first look, this cover seemed so obviously, very clearly fake
  12. Yet it’s not fake
  13. It’s real
  14. More than Google, the Mail are aiding terrorists by pointing out how to find “manuals” online
  15. While subsets of Google (most notably AdSense) can be legitimately criticised for profiting from terrorism, the Mail is specifically going at Google dot com
  16. Again, do they want to ban Google dot com?
  17. Do they want to ban cars?
  18. Do they want to ban search results about cars?
  19. Because if so, where will that one guy from primary school get his latest profile picture from?
  20. Are they suggesting we use Bing?
  21. Why are they, once again, focusing on the perpetrator instead of the victims?
  22. The Mail is 65p
  23. It is hard to believe that there is a single person alive, Mail reader or not, that can agree with this headline
  24. Three people wrote this article
  25. Three people took two minutes to find out cars can drive into people
  26. Trees had to die for this to be printed
  27. It is the front cover of the Mail

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