Keeping particle physics lively, stimulating, and maybe more…

A recurring theme at last week's Council meetings was the request I received to pass on Council’s heartfelt thanks to all the CERN community for the successful period we are currently enjoying, and it is my pleasure to do so. Council's request also serves as a timely reminder that CERN is more than the LHC, and the LHC is more than the machine and its four big experiments.


Earlier this week, one of the smaller LHC experiments, TOTEM, published its first results. TOTEM's paper contains measurements that are vital for a full understanding of hadron collider physics, as well as for topics in particle astrophysics. They continue a CERN tradition that goes back to the world's first hadron collider, CERN’s Intersecting Storage Rings (ISR).

One of the most significant results from the ISR was the unexpected observation that the cross-section for proton-proton collisions rises with energy. Put another way, it appears that the proton gets larger the more energetic it becomes. The ISR's results have since been confirmed and extended at other colliders, and the TOTEM result now takes that measurement to LHC energies. TOTEM's measurement is in good agreement with the simulation models that the big LHC experiments use to interpret their results. The importance of the measurement, however, is that the cross-section’s dependence on energy cannot yet be calculated from first principles, so no matter how much faith we have in our simulation models, nothing can replace a real measurement. The TOTEM result is not only interesting physics in its own right, it also provides vital experimental underpinning to results yet to come from the LHC’s big four.

Another CERN facility making the news this week is the CERN Neutrinos to Gran Sasso project, which supplies beams to the ICARUS and OPERA experiments at Gran Sasso. For the last three years, the OPERA collaboration has been measuring the time it takes neutrinos to cover the 730 km from CERN to Gran Sasso, and the result has come as something of a surprise. Taken at face value, the neutrinos appear to be travelling faster than the speed of light, Nature's speed limit. If confirmed, this would be a truly remarkable result, but before shredding the textbooks, independent observations and measurements are needed. That’s why OPERA has announced its results today at and through a seminar at CERN: to invite open scrutiny of its measurements.  

To end where I began, it is my pleasure to convey Council's thanks to the whole CERN community for keeping particle physics stimulating, lively, and who knows, perhaps even revolutionary. Only time will tell.

Rolf Heuer



Multimedia material produced by CNRS, INFN and CERN on the Opera's result:

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Videos produced by CNRS: French and English versions