Symmetries in particle physics
Symmetries in particle physics
Symmetries in particle physics
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Discrete symmetries:<br />
Parity<br />
Helicity, chirality, and all that<br />
Note: Reflections turn left-handed coord<strong>in</strong>ate systems<br />
<strong>in</strong>to right-handed ones and vice versa, this affects<br />
sp<strong>in</strong>s etc.<br />
More physical def<strong>in</strong>ition: Def<strong>in</strong>e handedness as sp<strong>in</strong><br />
with respect to the axis of motion (technically<br />
speak<strong>in</strong>g, this is helicity). For massive <strong>particle</strong>s this is<br />
not Lorentz-<strong>in</strong>variant, but for massless ones it is.<br />
Therefore, helicity is a mean<strong>in</strong>gful, fixed property of<br />
massless <strong>particle</strong>s, called chirality.
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