https://en.formulasearchengine.com/index.php?action=history&feed=atom&title=Bulk_Richardson_numberBulk Richardson number - Revision history2026-05-03T18:22:00ZRevision history for this page on the wikiMediaWiki 1.43.0-wmf.28https://en.formulasearchengine.com/index.php?title=Bulk_Richardson_number&diff=8956&oldid=preven>Nebelmeister: /* Formula */ Mistakenly copied the wrong formula and reference, I corrected both.2013-10-09T20:28:02Z<p><span class="autocomment">Formula: </span> Mistakenly copied the wrong formula and reference, I corrected both.</p>
<p><b>New page</b></p><div>{{Unreferenced|auto=yes|date=December 2009}}<br />
{{Flavour_quantum_numbers}}<br />
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'''Charm''' (symbol ''C'') is a [[flavour (physics)|flavour]] [[flavour quantum number|quantum number]] representing the difference between the number of [[charm quark|charm]] [[quark]]s ({{SubatomicParticle|charm quark}}) and charm antiquarks ({{SubatomicParticle|Charm antiquark}}) that are present in a particle:<br />
:<math>C = n_\text{c} - n_{\mathrm{\overline{c}}}.\ </math><br />
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By convention, the sign of flavour quantum numbers agree with the sign of the [[electric charge]] carried by the quark of corresponding flavour. The charm quark, which carries an electric charge (''Q'') of +{{Frac|2|3}}, therefore carries a charm of +1. The charm antiquarks have the opposite [[charge (physics)|charge]] ({{Nowrap|''Q'' {{=}} &minus;{{Frac|2|3}}}}), and flavour quantum numbers ({{Nowrap|''C'' {{=}} &minus;1}}).<br />
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As with any flavour-related quantum numbers, charm is preserved under [[strong interaction|strong]] and [[electromagnetic interaction]], but not under [[weak interaction]] (see [[CKM matrix]]). For first-order weak decays, that is processes involving only one quark decay, charm can only vary by 1 ({{Nowrap|{{!}}''C''{{!}} {{=}} ±1}}). Since first-order processes are more common than second-order processes (involving two quark decays), this can be used as an approximate "[[selection rule]]" for weak decays.<br />
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==See also==<br />
* [[Isospin]]<br />
* [[Strangeness (particle physics)|Strangeness]]<br />
* [[Bottomness]]<br />
* [[Topness]]<br />
* [[Hypercharge]]<br />
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==Further reading==<br />
* [http://arxiv.org/PS_cache/arxiv/pdf/0906/0906.1271v2.pdf Lessons in Particle Physics] Luis Anchordoqui and Francis Halzen, University of Wisconsin, 18th Dec. 2009<br />
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{{DEFAULTSORT:Charm (Quantum Number)}}<br />
[[Category:Particle physics]]<br />
[[Category:Quarks]]<br />
[[Category:Particle physics flavour quantum number]]<br />
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{{Physics-stub}}<br />
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[[de:Flavour#Quark-Flavours]]</div>en>Nebelmeister