UH Physicists Look for Answers to Questions about the Universe

Experiments Involving Neutrinos and Leptons May Offer Answers to Fundamental Questions

Three University of Houston physicists will share a $1.2 million grant from the Department of Energy, money they will use to continue work on separate but related experiments involving subatomic particles that could yield answers about the fundamental nature of the universe.

Physics professor Kwong Lau and Lisa Whitehead, assistant professor of physics, have been involved with an international group of scientists studying neutrinos at Daya Bay in China since 2007.

That project has made several significant discoveries, and Lau will use his portion of the grant to continue the work. His involvement has included five years as chairman of a board representing all of the institutions involved in the project; he continues to serve on the board.

Lau also led work to design a detector shield to eliminate cosmic rays that would interfere with the experiments.

Neutrinos, subatomic particles with no electric charge, can move through space, rock and even people without causing harm, and even without anyone noticing. There are three types, or flavors, of neutrinos – electron, muon and tau – and the particles morph between types as they travel.

As scientists learn more about how neutrinos change, they hope to understand the essential questions of the universe, including why it contains more matter than antimatter, making existence possible, Lau said.

“Theoretically, the Big Bang would have resulted in equal numbers of both, canceling each other out,” he said.

Whitehead began working with neutrinos during graduate school and continued her work during post-doctoral research at Brookhaven National Laboratory. Her research at Daya Bay is funded by a $750,000, five-year Early Career award from the Energy Department, which she received in 2012.

She is the convenor of the muon working group at Daya Bay. While that work continues, Whitehead’s portion of the new grant will go toward her role with a new multi-institution project at the Fermi National Accelerator Laboratory outside Chicago.

The Long-Baseline Neutrino Experiment will take a beam of neutrinos and send it through the earth to a target 800 miles away in South Dakota, to observe muon neutrinos converting to electron neutrinos. As with the work at Daya Bay, the results should shed light on matter/antimatter asymmetry, Whitehead said.

Physics professor Ed Hungerford is working on a third project, known as Mu2e, also based at the Fermi National Accelerator Laboratory, to observe the possible conversion of charged muon leptons to electrons.

That’s not supposed to happen, Hungerford said. While electron neutrinos can convert to muon neutrinos, and vice versa, the standard model of particle physics holds that charged particles, including muons, don’t convert. 

“We know neutrinos do change, but the charge particles don’t, at least in the standard model of particle physics,” he said. But there must be extensions of the model to account for several physical processes that scientists know occur, he said, including the fact that more matter than antimatter exists.

The project was conceived more than a decade ago and then shelved as too expensive before being resurrected by the Energy Department. Hungerford also was involved with the original proposal; he said construction is expected to begin next year, with data collection expected to begin by 2019.