The candidate particle may not belong to the standard model of particle physics, physicists' best theory for how particles and forces interact. Instead, some say it might be the first hint of a new force of nature, called technicolour, which would resolve some problems with the standard model but would leave others unanswered.
The observation was made by Fermilab's CDF experiment, which smashes together protons and antiprotons 2 million times every second. The data, collected over a span of eight years, looks at collisions that produce a W boson, the carrier of the weak nuclear force, and a pair of jets of subatomic particles called quarks.
Physicists predicted that the number of these events – producing a W boson and a pair of jets – would fall off as the mass of the jet pair increased. But the CDF data showed something strange (see graph): a bump in the number of events when the mass of the jet pair was about 145 GeV.