The fourth in a series of films following a team of physicists involved in research at the new Large Hadron Collider (LHC) at CERN in Switzerland.

'Problems' travels to Paris for a look at some of the theoretical work behind the 'Eurostar' paper. Gavin and his PhD student Mathieu explore the mathematics behind the behaviour of fundamental particles, and we have an update on the 'incident' which is holding up work at the LHC.

For an introduction to the 'Eurostar' project, watch Episode 1, and for more info and to sign up for future episodes, please visit the project website at collidingparticles.com