ATLAS/CERN

After years of effort, physicists spot Higgs boson decaying in most ordinary way

Physicists working with the world’s biggest atom smasher have spotted their newest, weirdest particle—the Higgs boson—decaying in the way it does most of the time. A single subatomic particle weighing as much as 130 protons, the Higgs lasts for a mere 10-trillionths of a nanosecond before it decays into less massive particles. Now, physicists have spotted the Higgs decaying into a particle called a bottom quark and its antimatter counterpart, an antibottom quark, (illustrated above) researchers working with the Large Hadron Collider (LHC) at the European particle physics laboratory, CERN, near Geneva, Switzerland, reported today.

Higgs bosons are thought to decay into a bottom-antibottom pair 57% of the time. Ironically, observing that decay has proved difficult, as the extremely messy collisions at the LHC generate copious bottom quarks and antibottom quarks that obscure the desired signal. When physicists discovered the Higgs 6 years ago, it was through rarer decays, such as a Higgs disintegrating into two photons, which theory predicts happens only 0.2% of the time.

The Higgs is central to physicists’ complicated explanation of how all other fundamental particles get their mass. The observation marks a key step in scientists’ campaign to see whether the boson really does decay into the various combinations of particles at the rates predicted by their standard model. If the decay rates don’t match the theoretical predictions, it would be a sure sign that new particles remain to be discovered and might lie within the LHC's grasp. 

*Correction, 29 August, 10:30 a.m.: The story has been updated to correct the predicted probability that a Higgs will decay to two photons.