NASA Astronomy Picture of the Day Collection

Sudbury Indicates Nonstandard Particle Model

The Sudbury Neutrino Observatory [ http://www.sno.phy.…] (SNO) has been detecting so few neutrinos [ http://www-e815.fna…] from the Sun [ http://www.nineplan…] that the Standard Model [ http://www2.slac.st…] of fundamental particles [ http://www2.slac.st…] in the universe may have to be revised. Pictured above [ http://www.sno.phy.…] is the SNO as it was being built. Now operating, this large sphere beneath Canada [ http://www.cia.gov/…] is detecting nearly invisible particles called neutrinos [ http://wwwlapp.in2p…] being emitted from the center of the Sun [ http://antwrp.gsfc.…]. SNO [ http://antwrp.gsfc.…] appears to be measuring a rate expected for all types of neutrinos [ http://www.ps.uci.e…] combined but a decided deficit for the electron neutrino [ http://www.treasure…]. The results [ http://www.sno.phy.…] are being interpreted as bolstering previous evidence [ http://antwrp.gsfc.…] that different types of neutrinos are changing into each other. The most popular model for fundamental particles [ http://www.cpepweb.…], known as the Standard Model [ http://www.lns.corn…], did not predict such schizophrenic neutrinos [ http://www.sno.phy.…]. Implications include [ http://xxx.lanl.gov…] that neutrinos have mass [ http://cupp.oulu.fi…] and therefore comprise some of the dark matter [ http://www.sciam.co…] in the universe, although probably not a cosmologically significant amount.

A. B. McDonald (Queen's University [ http://www.queensu.…]) et al., The Sudbury Neutrino Observatory Institute [ mailto:snoinfo@neutr ino.phys.laurentian. ca ]

Sudbury

neutrinos

particle physics

Canada

Goddard Space Flight Center (GSFC)

Sun

http://antwrp.gsfc.…

SPD-APOD-ap010710