Long-sought decay of Higgs boson observed: CERN

Six years after its discovery, the Higgs boson has at last been observed decaying into fundamental particles known as bottom quarks, scientists at CERN announced today.

The finding, presented by the ATLAS and CMS collaborations at the Large Hadron Collider (LHC), is consistent with the hypothesis that the all-pervading quantum field behind the Higgs boson also gives mass to the bottom quark.

LHC is the world's largest and most powerful particle accelerator situated in a tunnel beneath the FranceSwitzerland border near Geneva.

The Standard Model of particle physics predicts that about 60 per cent of the time a Higgs boson will decay to a pair of bottom quarks, the second-heaviest of the six flavours of quarks, CERN said in a statement.

Testing this prediction is crucial because the result would either lend support to the Standard Model - which is built upon the idea that the Higgs field endows quarks and other fundamental particles with mass - or rock its foundations and point to new physics.

"This observation is a milestone in the exploration of the Higgs boson," said Karl Jakobs, spokesperson of the ATLAS collaboration.

"It shows that the ATLAS and CMS experiments have achieved deep understanding of their data and a control of backgrounds that surpasses expectations," said Jakobs.

Spotting this common Higgs-boson decay channel is anything but easy, as the six-year period since the discovery of the boson has shown, said CERN researchers.

The reason for the difficulty is that there are many other ways of producing bottom quarks in proton-proton collisions, they said.

This makes it hard to isolate the Higgs-boson decay signal from the background "noise" associated with such processes.

By contrast, the less-common Higgs-boson decay channels that were observed at the time of discovery of the particle, such as the decay to a pair of photons, are much easier to extract from the background.

To extract the signal, the ATLAS and CMS collaborations each combined data from the first and second runs of the LHC.

They then applied complex analysis methods to the data.

The upshot, for both ATLAS and CMS, was the detection of the decay of the Higgs boson to a pair of bottom quarks.