University of Regina physicists’ work on identifying and measuring the high energy, subatomic particles called neutrinos may ultimately help unlock cosmic-scale mysteries, such as that of the fate of the universe.

A scholarly paper titled “Can gravity distinguish between Dirac and Majorana neutrinos?” and written by post doctoral physics researcher Dinesh Singh and his colleagues Nader Mobed, and Giorgio Papini, will be published in the August 4, 2006 edition of the weekly Physical Review Letters, a prestigious interdisciplinary physics journal.

In the paper the U of R physicists perform a calculation involving neutrinos and gravity which leads to predictions that may be verified by future measurements of neutrino oscillations. The measurements would distinguish between the two types of neutrinos – Dirac and Majorana – while at the same time allowing scientists to measure the particles’ masses. Scientists have been puzzled for years about whether neutrinos are Dirac or Majorana, since answering this question is crucial to discovering the fundamental nature of matter in the universe. The calculation would form part of the answer to one of the biggest riddles in the cosmos. Will the universe continue to expand forever? Or will it, one day eons from now, collapse on itself?

Singh says neutrinos were once thought to have no mass, but there is now strong evidence to suggest otherwise. “We know from experiments at the Sudbury Neutrino Observatory (SNO, a research facility built in an abandoned mine near Sudbury, funded in part by the Canadian government) that neutrinos experience a process called neutrino oscillation,” he says. “One kind of neutrino can spontaneously change into another kind while traveling through space. The only viable way to explain this effect is to suppose that the different kinds of neutrinos have distinct masses.”

But while SNO has yielded evidence that neutrinos oscillate, this finding has not offered a method of distinguishing between Dirac and Majorana neutrinos, nor does it currently provide enough information to measure the masses accurately. Singh, Mobed and Papini anticipate that SNO’s planned experiments within the next four to five years will provide the opportunity to observe the predictions made by the U of R physicists.

“If we are right, it will bring us a step closer to being able to account for the mass of the universe,” says Singh. “Currently, we can identify only 10 per cent of it, due to known stars and galaxies in the universe. It is very unlikely that neutrinos will account for all of the 90 per cent of the missing mass in the universe. However, what we can say for certain is that we can account for some part of the 90 per cent once we know the neutrino mass and combine that with a reliable figure of their abundance in the early Universe.”

U of R Physics Department head Zisis Papandreou says the publication of the paper in Physics Review Letters signals that the work is internationally significant.

“The physics of neutrinos is one of the hot topics in subatomic physics, cosmology and astrophysics research worldwide and particularly within Canada, with profound overtones in our understanding of the universe,” says Papandreou. “Theoretical work such as this contributes to the extraction of relevant experimental quantities that will ultimately elucidate such fundamental yet unresolved subjects.”

Singh will present the research at the 11th Marcel Grossman Meeting – an international physics conference specializing in gravity, to be held in Berlin July 23-29. For further information, contact Singh at (306)527-2034 or singhd@uregina.ca.