University scientists unraveling nature of Higgs boson

"In nature, there are two types of particles: fermions and bosons," said Ketino "Keti" Kaadze, a research associate at Fermilab who in August is joining the faculty at Kansas State University's physics department. "Fermions, quarks and leptons make up all the matter around us. Bosons are responsible for mediating interaction between the elementary particles."

Building on the full data collected in 2011 and 2012, part of which was used to identify the Higgs boson's existence, researchers see evidence that the Higgs boson decays into fermions. This also was predicted in 1964 but not observed until after the Higgs boson was identified in 2012, Kaadze said.

The observation is key in reinforcing what is theorized about the Higgs boson and is a steppingstone to building on more extensive knowledge about how the universe works, Kaadze said.

"We think that the Higgs boson is responsible for the generation of mass of fundamental particles," Kaadze said. "For example, the electrons acquire their mass by interacting with the Higgs boson. As electrons are not massless, they form stable orbits around nuclei, thus allowing the formation of electrically neutral matter from which the Earth and all of us are made. Even slight changes of the masses of fundamental particles around us would change the universe very drastically, and the Higgs boson is the centerpiece that ties it all together."

Kaadze, along with other scientists, was part of a team that looked for the Higgs boson decaying to a pair of tau leptons -- fermions that are very heavy equivalents of electrons. A second team also searched for the Higgs boson decaying into a pair of heavy fermions, called beauty quarks. These two decay signatures offer the highest discovery potential, she said.

The findings appear in the journal article, "Evidence for the direct decay of the 125 GeV Higgs boson to fermions."

Kaadze is one of the several researches in Kansas State University's physics department heavily involved in research at the European Organization for Nuclear Research, or CERN. Their research is conducted with the Compact Muon Solenoid, one of the Large Hadron Collider's two particle detectors that help scientists at CERN to search for evidence for Higgs boson.

Other Kansas State University physics faculty members involved in CERN research include Tim Bolton, professor; Andrew Ivanov, assistant professor; and Yurii Maravin, associate professor.

The Higgs boson was the last key component needed to confirm the Standard Model of particle physics: a low-energy theory that explains the workings of the universe at the smallest length scales.

Efforts are currently underway to nearly double the center-of-mass energy at CERN. Doing so will increase the ability to create Higgs bosons. In turn, scientists can build on data in an effort to explain the mysteries of the universe.

"We know that the Standard Model of physics that we have now does not explain some puzzles in nature," Kaadze said. "We know there has to be other models that can explain phenomena like dark matter and dark energy, and why we can have different generations of the same particle that are identical except for their mass. Finding the Higgs particle wasn't the end of the story. It was the starting point on a new horizon."