Photo: Reidar Hahn
When he was 16, Alex Himmel had his first job at Fermilab as a summer student. He’s been investigating particle physics ever since, and this year he received the Universities Research Association Thesis Award for his research on muon antineutrino oscillations at Fermilab’s MINOS experiment.
As a doctoral student at Caltech, Himmel researched muon neutrinos at MINOS. In his data, he found measurements suggesting that muon antineutrinos in the MINOS beam behaved differently than muon neutrinos.
“Originally, nobody cared about antineutrinos,” said Himmel, now a postdoctoral fellow at Duke University. “We started looking at the antineutrinos that were just there in the beam, and after seeing something a little strange, we decided to dedicate ourselves to the antineutrino signal.”
Himmel and his collaborators used a beam made only of antineutrinos to study their behavior. Other scientists initially pushed back, he said, since they had assumed muon antineutrinos would follow charge-parity symmetry and behave exactly like muon neutrinos. They believed that, for advancing particle physics, other measurements were more pressing.
But what Himmel found was evidence that muon antineutrinos did not oscillate as frequently as muon neutrinos – a possible break from the CP symmetry predicted by the Standard Model.
“The award is a nice validation that the physics was ultimately interesting to the community,” Himmel said.
Bob Zwaska, who chairs the URA Thesis Award committee, said Himmel’s research was a significant part of the MINOS program. The award committee selected Himmel’s thesis from 19 nominations across Fermilab from all fields.
“You would think that neutrinos and antineutrinos behave similarly in this search,” Zwaska said, “but he studied the differences and found hints that took quite a bit of effort to tease out.”
Those hints linger on, and while Himmel said further research at MINOS has suggested that muon neutrinos and muon antineutrinos are more similar than not, he added that the NOvA experiment has the potential to better define their individual characteristics.
“Alex is certainly worthy of this award,” said Marta Cehelsky, executive director of URA. “He was a terrific candidate, and this is an impressive piece of work.”