单词 | pion |
释义 | pion[ pahy-on ] / ˈpaɪ ɒn / noun Physics.the first meson to be discovered: it has spin 0 and may be positively or negatively charged or neutral; charged pions decay into a muon and a neutrino or antineutrino. Symbol: π Also called pi meson. Origin of pionFirst recorded in 1950–55; pi (meson) + -on1 Words nearby pionpinyon jay, Pinza, Pinzón, PIO, piolet, pion, pioneer, Pioneer Day, piopio, piosity, pious Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020 Example sentences from the Web for pionBritish Dictionary definitions for pionpion pi meson/ (ˈpaɪɒn) / nounphysics a meson having a positive or negative charge and a rest mass 273.13 times that of the electron, or no charge and a rest mass 264.14 times that of the electron Word Origin for pionC20: from Greek letter pi 1 + on Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Scientific definitions for pionpion [ pī′ŏn′ ] A meson occurring either in a neutral form with a mass 264 times that of an electron and a mean lifetime of 8.4 X 10-17 seconds or in a positively or negatively charged form with a mass 273 times that of an electron and a mean lifetime of 2.6 X 10-8 seconds. The pion was once believed to be the particle that mediates the strong force, which holds nucleons together in the nucleus; it is now believed that the gluon is the mediator particle. Pions do interact with nucleons, however, and are able to transform neutrons into protons and vice versa. Also called pi-meson See Table at subatomic particle. The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved. |
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