Higgs boson observed decaying into pairs of b quarks

By Brooks Hays
The ATLAS detector at CERN's LHC facilities in Switzerland. Photo by Maximilien Brice/Wikimedia Commons
The ATLAS detector at CERN's LHC facilities in Switzerland. Photo by Maximilien Brice/Wikimedia Commons

July 10 (UPI) -- Physicists have observed the Higgs boson decaying into a pair of b quarks, confirming the predictions of the Standard Model of particle physics.

The Higgs boson is an elementary particle essential to the Standard Model. It is associated with the Higgs field, an energy field that gives particles their mass.


Scientists use particle accelerators to smash particles against each other, yielding a variety of exotic and subatomic particles. ATLAS is one of six particle accelerators at CERN's Large Hadron Collider facilities in Switzerland.

Simulations suggest the Higgs boson should decay into a pair of b quarks roughly 60 percent of the time, but physicists have struggled to observe the decay.

The new ATLAS experiment results -- presented this week at the 2018 International Conference on High Energy Physics in Seoul, South Korea -- revealed a Higgs-boson-to-b-quarks decay rate in agreement with Standard Model predictions.

Traditional methods for production of the Higgs boson yield b quarks, making it difficult to distinguish the production byproduct from decay. Scientists regularly witnessed the Higgs boson decaying into photons, tau-leptons, and W and Z bosons, but b quarks proved hard to see.


Physicists with ATLAS continually tweaked the production process to reduce the number of background interactions yielding b quarks.

After much experimenting, scientists were able to reduce the background noise enough to focus in on the b quarks produced by decay.

While the recent observations are in agreement with the Standard Model, the new method for honing in on only the particle collisions of interests will allow scientists to further probe particle physics theories.

"With these observations, a new era of detailed measurements in the Higgs sector opens up, through which the Standard Model will be further challenged," researchers wrote in a news release.

"Studies of this new decay will open a whole new window onto the Higgs, and may also provide hints of new physics beyond our current theories," scientists added.

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