UCR physicists contribute to major Higgs boson discovery

On Aug. 28, the European Organization for Nuclear Research, known as CERN, announced that two experiment teams at the Large Hadron Collider discovered decay in the Higgs boson particle, an integral component of our universe, that was found by scientists at the center in 2012.

UC Riverside physicists Gail Hanson, Robert Clare, Stephen Wimpenny, Bill Gary, and Owen Long, work on one of the experiments, known as Compact Muon Solenoid, or CMS. The new results, which show the Higgs boson decays into fundamental particles known as bottom quarks, are an important milestone for the field of high-energy physics.

Both CMS and the other experiment, ATLAS, finally saw evidence of the Higgs decaying to bottom quarks that exceeds the 5-sigma threshold of statistical significance typically required to claim a discovery. This represents a big step forward in the quest to understand how the Higgs enables fundamental particles to acquire mass. Both teams found their results were consistent with predictions based on the Standard Model.

Higgs bosons are only produced in about one out of 1 billion Large Hadron Collider collisions and survive only 1 septillionth of a second before their energy is converted into a cascade of other particles, such as bottom quarks. Because it’s impossible to see Higgs bosons directly, scientists use secondary particles to study the Higgs’ properties.

Hanson, a distinguished professor of physics and co-chair of the Higgs Publication Committee, worked on reviewing the research paper that announced the findings, submitting it for publication, and getting previous publications in this research area reviewed, submitted, and published.

“Bottom quarks are identified by their relatively long lifetimes using algorithms based on the silicon tracking system, on which many UCR graduate students and postdocs work,” Hanson said.

Hanson and her UCR colleagues work with physicists in all of CMS, particularly on the publication committee. A group Hanson leads specializes on the very precise CMS tracker, made entirely of silicon detectors, which is necessary to identify bottom quarks.

Theory predicts that 60 percent of Higgs bosons decay into bottom quarks. Finding and understanding this transformation is critical because it opens up the possibility to examine the behavior of the Higgs, including whether it could interact with new, undiscovered particles.

The next step for the ATLAS and CMS teams is to increase the precision of measurements to study the decay of the Higgs into bottom quarks with a much greater resolution and explore what secrets the Higgs boson might be hiding.

-Iqbal Pittalwala

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