A rumoured encounter with the Higgs boson, also known as the "God particle", at the Large Hadron Collider (LHC) near Geneva has led to hysteria among some scientists.
However experts have urged caution over a leaked internal memo, warning it could well be a false alarm.
Finding the Higgs is one of the main goals of the LHC, a 17-mile underground tunnel.
The Higgs was proposed in the 1960s to explain why matter has mass and is the missing piece of the standard model of particle physics. Speculation has now run wild on the internet after an anonymous note was posted on the blog of Columbia University mathematician Peter Woit.
The memo revealed that one of the LHC detectors had picked up a signal consistent with what Higgs is expected to produce.
The scientists noted that "the present result is the first definitive observation of physics beyond the standard model".
But Cern, the European organisation for nuclear research, stressed the note was only preliminary.
Spokesman James Gillies said it was "way, way too early" to confirm whether Higgs had been detected, and he told Wired magazine: "The vast majority of these notes get knocked down before they ever see the light of day."