Word of the Week: Look Elsewhere Effect

August 12, 2011

The "look elsewhere" effect is a common but easily-overlooked bias in statistical analyses that can have a major impact on searches for the most uncommon of prey: rare subatomic particle, including the current search at the Large Hadron Collider for the Higgs boson.

The phrase"look elsewhere" refers to the fact that a widely-cast net is sure to pull in something, but it could be a prize fish, or it could be an old tire. To put it in particle physics terms, looking for the Higgs in a broad range of masses  – the LHC has been looking between about 110 GeV and 600 GeV, a range of almost 500 billion electron volts – is bound to turn up some bumps in the data. But are these bumps Higgs bosons, or statistical fluctuations?

In fact, bumps seen in recent LHC results, have been termed "interesting", but researchers are careful not to say more. They know the question of whether the bumps are keepers or should be thrown back into the sea of background noise needs time, and data, to answer.