Iowa State physicists contribute to Higgs Boson analysis, understanding

It's supposed to happen most of the time a Higgs boson shows up in the Large Hadron Collider. But, even with their huge and high-tech particle detectors, physicists around the world hadn't been able to see the Higgs decaying into two bottom quarks.

The Standard Model of particle physics predicts that when the proton-proton collisions at the collider produce Higgs bosons, 58 percent of the time those bosons would ultimately decay into a pair of bottom quarks. (The various quarks are the matter particles that make up the protons and neutrons inside the nuclei of atoms. Physicists believe the Higgs is associated with the field that gives elementary particles such as quarks their masses.)

But, inside the 17-miles-around collider near Geneva, Switzerland, collisions of protons racing at nearly the speed of light and at unprecedented energies produce billions of pairs of bottom quarks that have nothing to do with the Higgs.

And so, ever since the Higgs was discovered in 2012 – observed as it decayed into pairs of photons, tau-leptons, and W and Z bosons – physicists have been working to find a way to separate the Higgs-related bottom quarks from all the others.

Iowa State University physicists have been part of that international effort.

"The problem is, you can't build a Higgs on demand," said Soeren Prell, an Iowa State professor of physics and astronomy and a member of the Iowa State research team working on the ATLAS Experiment at the collider. "We smash protons together and very few times will we get a Higgs."

He said physicists poring over 2015 and 2016 data collected by the ATLAS particle detector found ways to sort and separate bottom quarks. Those produced by Higgs decay are associated with the weak force of particle physics. All the other bottom quarks are associated with the strong force.

Carlos Vergel Infante, an Iowa State doctoral student, helped explore new ideas for trigger technology that identifies and saves the Higgs-related data. Jie Yu, a postdoctoral research associate, helped do the statistical analysis that confirmed physicists have enough data to say they have evidence of the Higgs decaying into bottom quarks. They'll need more evidence to statistically claim an observation and discovery.

A paper describing the evidence so far has been written by the ATLAS collaboration and submitted for review and publication.

Provided by Iowa State University