UK News from CERN Issue 61

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UK news from CERN Issue 6: 9 October 2012

In this issue:     

Inside ALICE – the hottest place on the planet Keeping the drama out of a crisis - CERN engages UK crisis management consultants Researcher’s Night – staying up late for physics Tarte au framboise – introducing Raspberry Pi to French schools Dates for the diary

Inside ALICE – the hottest place on the planet The Higgs boson has been widely billed as ‘the particle which gives matter mass’. It does, but it’s only responsible for 2% of your mass. What about the remaining 98%? The ALICE experiment on the LHC is creating extreme conditions that are forcing nature to give up some of her secrets – the properties of the Strong Force that keeps particles inside the atomic nucleus together, and how this energy generates mass. In fact ‘extreme’ seems a rather inadequate description of temperatures that are 300,000 times hotter than the inside of the Sun (6 trillion °C) and densities that are 50 times greater than those in the core of a neutron star. Only black holes have a higher density.

The ALICE experiment © CERN

We know that the Strong Force imprisons quarks in protons and neutrons inside the nucleus, but it is the force that we know least about. We have a theory, Quantum Chronodynamics or QCD, which explains the basics but as David Evans from University of Birmingham,

and a member of the ALICE Management Board explains, it leaves a lot of questions unanswered; “The equations involved in QCD are extremely complex, and ‘explode’ under certain conditions. Free quarks don’t exist in nature, but QCD predicts that they do at the kinds of temperatures and densities that existed at the start of the Universe. ALICE allows us to recreate conditions that existed only 10-5 seconds after the Big Bang.” For one month each year, the LHC accelerates two beams of highly charged lead ions – lead atoms stripped of all 82 of their electrons. When they collide, the beams of ions create subatomic fireballs in the heart of the ALICE experiment. Measurements show that the resulting temperatures and densities are the highest ever created on Earth. A sugar-lump sized piece of this primordial soup of quark gluon plasma would weigh 40 billion tonnes. By accurately recording what happens in each of the collisions, David and his colleagues hope to find out more about the Strong Force. And that’s quite an undertaking as each collision generates over 10,000 particles, and thousands of collisions happen every second. The trigger electronics for the data acquisition system were designed by the University of Birmingham and built by UK company, Cemgraft. “The UK is a relatively small group in the ALICE collaboration but we have a big influence. The trigger electronics is the only central system for the experiment in which CERN has no involvement – it’s a reflection of how highly we are trusted.”

Page 1 Written and edited by Stephanie Hills, STFC Communications and Innovation Officer @ CERN Stephanie.hills@stfc.ac.uk or Stephanie.hills@cern.ch


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