Mark Chen’s area of specialization is particle astrophysics. Cosmologists already know that particle properties deeply influence the evolution of the universe: from the time of inflation, through big bang nucleosynthesis, into the formation of galaxies and other structures, and into the present.
One of Chen’s involvements is with the Sudbury Neutrino Observatory (SNO), a giant particle detector buried 2 km underground in an active nickel mine. In June 2001, collaborators announced that they had solved a 30-year-old mystery concerning apparently missing solar neutrinos. There are three types of neutrino, all of which are elementary particles of matter that are emitted by the billions by the nuclear reactions that fuel the Sun. Since the 1970s, several experiments have detected neutrinos arriving on Earth, but they have found only a fraction of the number expected from detailed theories of energy production in the Sun. SNO’s scientists have now discovered that electron neutrinos actually transform into other types of neutrinos while travelling from the Sun to Earth, and are therefore not ‘missing’ after all. This discovery also indicates that neutrinos have mass, and will be very important in reaching a greater understanding of the universe at the most microscopic level.
Chen is also involved in the exploration of ultra high-energy cosmic rays. A puzzling question in particle astrophysics relates to the origin and propagation of cosmic rays. At the highest energies, cosmic rays should be attenuated by the microwave background, and should not be detected from sources with distances greater than 150 million light-years. Experiments on Earth have observed over a dozen such energetic events that appear to defy this cut-off. Is this hinting at a particle physics breakthrough, or indicating that an energetic source in the vicinity of Earth may be the origin of fantastic cosmic acceleration? Chen is exploring novel ways to detect cosmic rays and neutrinos by attempting to detect the radio signals they produce when they strike the Moon, using the Giant Metrewave Radio Telescope in India.
NSERC John C. Polanyi Award, 2006
Premier’s Research Excellence Award, 2003
John S. Stemple Memorial Prize in Physics, 1993
Aharmim, B. et al. "Combined Analysis of all Three Phases of Solar Neutrino Data from the Sudbury Neutrino Observatory." Phys. Rev. C 88 (August 2013): 025501.
Chen, M.C. "Geoneutrino Detection." In Treatise on Geochemistry, edited by H.D. Holland and K.K. Turekian, 443–53. Vol. 15. 2nd ed. Elsevier, 2014.