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Tuesday
Jun282011

Quiet drama


 

 

You are a particle physicist who’s recently joined the Large Hadron Collider project in Geneva.   Protons – miniscule constituents of the atom are smashed into each other at huge energies to see what will happen. 

There’s a scary sense of entering a vast human system.....the first email you received was sent to 3,900 people.

What are you trying to do?  You’re looking for the famed and much reported Higgs particle.  Which is most likely to be seen in the accelerator as the decay of two photons and the energy of these need to be measured as accurately as possible so you can figure out that the Higgs caused them, remembering Einstein’s mass is energy, energy is mass.  Your focus is accurate measurement.

And the accelerator is running at half energy, smashing protons together a stunning 7 days a week, 24 hours a day.  This is enough to produce Higgs particles, but when full capacity is reached the likelihood increases.  Data just pours off continuously, is sorted and then visualised by computer programmes and summarised.  My mind’s eye leaps beyond the earth’s atmosphere to an isolated viewpoint in outer space to register this human activity: the re-enactment of the beginning and a new stone circle.

Everything that happens is predicted by the Standard Model , our anzatz, a kind of periodic table which lists all the particles we have ever found, the mathematics of how they collide and the forces between them and probabilities.  In fact you say, the whole world agrees with the Standard Model.....except one particle hasn’t been seen.   It is so incredibly important to find this particle. 

I furrow my eyebrows and ask the obvious question.  The Higgs gives us mass.   Everything in principle should be mass-less like photons travelling at the speed of light, but the Higgs slows things down.  It is everywhere, it pervades everything.  It is a uniform field everywhere that isn’t visible.  And of course I incredulously wonder out loud why we can’t detect this thing that is everywhere.  Well we need to put a lot of energy in to have the particle affects.  At big bang – Higgs particles would be whizzing around everywhere.  Not like now in our cool and complex universe. 

There is a very big question of why different particles have the masses they do.  We have the electron - e, the muon at 200 times the mass of e and the tau at 3,500 times e.   Interpret the question differently - why does the Higgs field slow down some things much more than others? You say it would be incredibly exciting if we fail to find Higgs – we may finally find what the numbers are.  There are 12 masses in the Standard Model and we don’t know how they came about.

‘It’s a quite fantastical business’, but at the end of a day as a scientist you’re busy soldering a wire on....And when I comment on how surreal this particle world seems you laugh and say, yes you still have to pay the mortgage and change nappies at the same time as trying to determine the fabric of the universe and why we exist in it.  And you do these experiments and the particles are really there.

And you show me some beautiful diagrams of particle tracks.  An electron and positron bounce off each other when they don’t collide head on; the faster they curve, you can tell the momentum and you read these like they are writing.

You got into physics when your dad got Scientific American and you read an article on particle physics and discovered you could get paid to do it.

I flick through your file of particle tracks and calculations and am struck as always by the beauty of Feynman diagrams.  You say how amazingly clever they are, a huge calculation and each one can be summarised into a diagram.  And I say, don’t you find the process weird adding up all the pathways something can happen.  Yes it’s nutty.....and circumstances are included where things run backwards in time and no one can intuit it.  Though you don’t worry about the weirdness on a day to day basis – the calculations give the right answers.  It is typical Feynman – beautiful physical visualisation.

I ask you what you’d like to tell people.  Tell people about our curiosity, we are wondering how the world works at a fundamental level.  It is like staring at the stars. 

When I ask you how much we know, you say the more you learn the more you realise you don’t know.  You never quite know what will happen.  Quantum Mechanics and Relativity hit and everything exploded.  In the next 2-3years we may find something that blows open the whole field again....like we make a dozen Higgs all acting in different way and we start again. 

The Large Hadron Collider is asking open questions, operating at energies close to those at a fraction of a second after the start of the universe. 

It is an incredible human drama that in some ways is very quiet.

 

Paul Dauncey is a particle physicist.  He specialises in developing particle detectors to hopefully show the Standard Model is wrong. He also runs.

Image: simulated Higgs decays