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n. pl. he·lic·i·ties Physics
1. The projection of a particle's spin vector in the direction of its momentum vector, being positive if it points in the same direction, and negative if it points in the opposite direction. Helicity is the chirality of the particle's spin.
2. An instance of such projection.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
n, pl -ties
(General Physics) physics the projection of the spin of an elementary particle on the direction of propagation
[C20: from helix + -ity]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014