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Meet the particle snipers (part 2)

 

LAST WEEK we marked the launch of the new ‘Collider’ exhibit at the Science Museum by straining a feeble sniper rifle metaphor and looking at what lay ahead for the most celebrated of the atom smashers – the Large Hadron Collider. 

We also took a glimpse at a proposed successor whose 100km accelerator ring would dwarf even the mighty LHC.

In week two of our particle sniper special we take a look at some of the more practical particle projects on the drawing board and explore some of the problems they will be training their sights on in the years to come. 

The only chemical elements created in the Big Bang were hydrogen, helium and lithium. 
In the nuclear furnaces at the heart of stars, these were transmuted into the heavier elements up to iron  (a process called nucleosynthesis). 
Even the most massive stars die when the fusion process reaches lead because lead fusion requires more energy than it liberates (fusion-liberated energy is the life blood of the stars).
Elements heavier than iron were created when the stars died in supernova explosions, which create enough heat and pressure to force iron to fuse into elements like gold and uranium.

The periodic table of elements is an icon – a list of atomic attributes that is as elegant as it is practical – as an at-a-glance guide to every chemical element, it is the scientific equivalent of the London Tube map. But it is far from complete.

It is supposed to be a complete list of all 98 naturally-occurring chemical elements (and 20 synthesised), but, according some estimates, there is somewhere between 3,500 to 7,000 elements missing. 

All the chemical elements heavier than iron are forged in the insane high-temperature, high-pressure conditions that exist when a star explodes as a supernova. But, although the stable elements, stuck around long enough to build the planets and you and me, the vast majority were so unstable that they stuck around for just a trillionth of a trillionth of a second before they decayed into lighter, more stable, elements and were lost forever.

Now scientists are preparing to build two new particle snipers that will have these ‘lost elements’ in their sights. To find them, they will have to recreate the violence of a supernova here on Earth.

The first, the Facility for Antiproton and Ion Research (Fair), will be built in Germany, while the second (whose acronym sounds like a bladder medication), the European Isotope Separation On-Line facility (Eurisol), could be built in Oxford. 

By smashing atoms of heavy elements, such as uranium, into each other (or into fixed targets), they will create temperatures more than a million times hotter than the Sun and enough pressure to (hopefully) produce some of the missing short-lived chemical elements and measure them before they decay away.

[Fair will smash together uranium nuclei (the heavy radioactive element). The collision will create a fireball that briefly reproduces the extreme heat and pressure of a supernova explosion – creating 1,000 new particles]

 

Last year’s discovery of the Higgs boson, was a vindication for the expense of the Large Hadron Collider and a triumph of theoretical and experimental science, but it was not the end of the Higgs-hunting story.

Although the LHC did a fine job of finding the Higgs, the discovery raised more questions than it answered.

For example, theoretical calculations predicted that the Higgs boson would have much more mass than the particle discovered at Cern – raising the possibility that the LHC’s Higgs is just one member of a larger Higgs family (there might be as many as five Higgs’).

To get to know Higgs better, will require the construction of a much more focused machine than the LHC. 

The International Linear Collider (ILC) will be a much more precise machine than the LHC. Instead of smashing protons together – which, because they are made of smaller particles, is a bit messy – the ILC will smash electrons into their antimatter equivalent, positrons. Because electrons and positrons are fundamental particles, they aren’t made of smaller ‘bits and pieces’ – this means there is less particle ‘mess’ for physicists to sift through. It also means that physicists will know exactly how much energy has gone into each collision – making the ILC very good at precisely measuring the masses and other characteristics of newly discovered particles.

 

Science has two theories that explain most of how the Universe works. On the atomic scale, they have the Standard Model (SM) and, on the galactic scale, they have Einstein’s General Relativity (GM). Individually, they are almost perfect, but, try as they might, physicists can’t make them work together. Gravity, as described by GM, doesn’t fit into SM’s atomic realm. To find the answer, physicists will have to seek out evidence of new physics beyond the Standard Model.

One planned particle sniper that could be capable of doing this is the ILC, another is the rather awesomely-named ‘Project X’. Like the ILC, this American atom smasher will use collisions between fundamental particles to probe the nature of matter in a more focused way than the LHC.

The device will use a high-intensity approach to probe the limits of the Standard Model. It will use streams of muons (the electron’s heavy-weight cousin) that are focused and accelerated into super-dense, laser-like beams.

One theory that seeks to integrate SM with the workings of the Universe at large is ‘Supersymmetry’ (or SUSY). This predicts that, for every particle described by SM, there exists a hidden, super-sized partner. If machines like Project X and the ILC can find evidence of SUSY, physicists will achieve a half-century-long ambition to unify all of physics under a single all-encompassing theory.

[According to supersymmetry, every fundamental particle should have a heavy-weight twin (or partner) particle. These ‘alter-ego’ super-particles would have much more mass than their ‘normal’ cousins and be very short-lived (quickly decaying into lighter particles). 

Some theories predict the existence of an electrically neutral (weakly interacting) and stable superparticle that could account for the missing mass of the Universe, known as dark matter]

 

The Large Hadron Collider is a regular visitor to the pages of MetroCosm and now you can visit the LHC yourself.

But you won’t need to travel to the Swiss/French border; nor will your claustrophobia be put to the test in a 100m-deep (330ft) tunnel while high-energy protons, pushed along by super-conducting magnets, whizz past you at 99.9999991 per cent the speed of light. The Science Museum has recreated the Cern experience in the heart of London.

The ‘Collider’ exhibit brings the science, technology and personalities behind the world’s greatest science experiment to life (albeit on a slightly smaller scale) and culminates by putting you at the centre of a wrap-around particle collision (on a very much larger scale) simulated from real data.

It even includes a video drama with a cameo from the world’s favourite celebrity particle botherer, Prof Brian Cox.

Collider is at the Science Museum until May 6 – www.sciencemuseum.org.uk