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An overbar marking a particle's antimatter counterpart.
Also known as: Antimatter bar, Overline particle notation
A bar over a particle symbol marks its antiparticle. For charged particles the sign is often used instead, but neutral particles have no sign to flip, so the bar is the only notation that works for all of them.
Marks the antiparticle of the symbol it covers, drawn as a bar over the letter.
Contexts: Laboratory
Is the general notation because neutral particles have no charge sign to reverse, so an antineutron can only be written with a bar.
Contexts: Laboratory
A short horizontal line ruled above a single letter, not touching it.