The standard model of particle physics is like Gormenghast - a sprawling castle constructed by tacking on new rooms as needed, with no underlying grand design. It was built to house a particle-level explanation for the entire universe and it succeeds on many counts.
Some physicists are now looking to tack on annexes to accommodate the Higgs boson, dark matter and the graviton, if they can be found (see "Inside the standard model"). Others think the structure needs an overhaul, and they have worked up new blueprints for magnificent palaces based on ideas such as string theory. Trouble is, it's almost impossible to tell whether these designs are realistic, or just fairy-tale constructions with clouds for foundations.
Even those who don't want to tear the castle down wouldn't mind testing its strength using some big artillery. That's the main reason for building the Large Hadron Collider (LHC), the brawniest of all particle experiments at the CERN laboratory near Geneva, Switzerland.
Yet several smaller groups are successfully using a gentler approach, tapping at the castle walls, feeling for weak points. Among these, one experiment stands out for identifying what may be the first major crack in the edifice of the standard model.
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