The Visual Guide to Extra Dimensions: The Physics Of The Fourth Dimension, Compactification, And Current And Upcoming Experiments by McMullen Chris

Author:McMullen, Chris [Desconhecido]
Language: eng
Format: epub, azw3
Publisher: Amazon Publishing
Published: 2014-11-03T02:00:00+00:00

9.1 Elementary Particles and Their Interactions

Ordinary matter – i.e. macroscopic material objects with which we are familiar – is composed of atoms consisting of protons and neutrons in the nucleus surrounded by electron clouds. The protons and neutrons themselves are composed of fractionally-charged particles called quarks. Specifically, a proton is a bound state of two up quarks and one down quark, while the neutron is a bound state of two down quarks and one up quark. An up quark has a charge of + 2e/3 and a down quark has a charge of – e/3, where e represents the charge of a proton (so –e corresponds to the charge of an electron). It is easy to check that the charge of two up quarks and one down quark equals the charge of a proton and, similarly, that the charge of two down quarks is canceled by the charge of the up quark in a neutron. Quarks are never observed to exist as free particles, but only form states with two or three quarks bound together as a single object, like the proton and neutron. The up quark and down quark have nearly equal masses, which explains why protons and neutrons have nearly equal masses. Since the neutron is slightly heavier than the proton, it follows that the down quark must be slightly heavier than the up quark. Up and down quarks, however, are much heavier than electrons. Quarks and electrons are evidently elementary particles – i.e. not made up of yet smaller constituents.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.