Kajita and McDonald win Nobel Physics Prize

Takaaki Kajita of Japan and Arthur McDonald of Canada were awarded the Nobel Physics Prize on Oct. 6 for resolving a mystery about neutrinos, a fundamental but enigmatic particle.

The pair were honoured for work that helped determine that neutrinos have mass, the Royal Swedish Academy of Sciences said.
 
"The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the Universe," it said.
 
The findings, it added, threw down a challenge to the so-called Standard Model -- the conceptual model of the particles and forces of the cosmos.
 
Neutrinos are lightweight neutral particles that are created as the result of nuclear reactions, such as the process that makes the Sun shine.
 
Next to particles of light called photons, they are the most abundant particles in the Universe.
 
Their existence was tentatively proposed in 1930, but was only proved in the 1950s, when nuclear reactors began to produce streams of the particles.
 
The prevailing theory was that neutrinos were massless, but experiments carried out separately by teams led by Kajita in Japan and McDonald in Canada showed that this was not the case.
 
Many neutrinos blasted out from the Sun -- a type called electron neutrinos -- "oscillated" en route to become cousin particles called muon-neutrinos and tau-neutrinos, they found.
 
Under the quirky rules of quantum physics, the identity change can only happen if the neutrinos have mass.
 
"This is of groundbreaking importance for particle physics and for our understanding of the Universe," the Nobel committee said.
 
"The experiments have... revealed the first apparent crack in the Standard Model. It...