Editing Electronvolt (section)

=== Mass ===
By [[mass–energy equivalence]], the electronvolt corresponds to a unit of [[mass]]. It is common in [[particle physics]], where units of mass and energy are often interchanged, to express mass in units of eV/''c''<sup>2</sup>, where ''c'' is the [[speed of light]] in vacuum (from [[Mass–energy equivalence|{{nowrap|1=''E'' = ''mc''<sup>2</sup>}}]]). It is common to informally express mass in terms of eV as a [[unit of mass]], effectively using a system of [[natural units]] with ''c'' set to 1.<ref>{{cite journal | bibcode=1983QJRAS..24...24B | title=Natural Units Before Planck | last1=Barrow | first1=J. D. | journal=Quarterly Journal of the Royal Astronomical Society | year=1983 | volume=24 | page=24 }}</ref> The [[kilogram]] equivalent of {{val|1|u=eV/c2}} is:

<math display="block">1\; \text{eV}/c^2 = \frac{(1.602\ 176\ 634 \times 10^{-19} \, \text{C}) \times 1 \, \text{V}}{(299\ 792\ 458\; \mathrm{m/s})^2} = 1.782\ 661\ 92 \times 10^{-36}\; \text{kg}.</math>

For example, an electron and a [[positron]], each with a mass of {{val|0.511|u=MeV/c2}}, can [[Annihilation|annihilate]] to yield {{val|1.022|u=MeV}} of energy. A [[proton]] has a mass of {{val|0.938|u=GeV/c2}}. In general, the masses of all [[hadron]]s are of the order of {{val|1|u=GeV/c2}}, which makes the GeV/''c''<sup>2</sup> a convenient unit of mass for particle physics:<ref>{{cite web|url=https://indico.cern.ch/event/318730/contributions/737345/attachments/613347/843809/gevtypeunitshst14.pdf |title=Energy and momentum units in particle physics| author=Gron Tudor Jones| website=Indico.cern.ch| access-date=5 June 2022}}</ref>
{{block indent|em=1.2|text={{nowrap|1={{val|1|u=GeV/c2}} = {{val|1.78266192|e=-27|u=kg}}.}}}}

The [[atomic mass constant]] (''m''<sub>u</sub>), one twelfth of the mass a carbon-12 atom, is close to the mass of a proton. To convert to electronvolt mass-equivalent, use the formula:
{{block indent|em=1.2|text={{nowrap|1=''m''<sub>u</sub> = 1 Da = {{val|931.4941|u=MeV/c2}} = {{val|0.9314941|u=GeV/c2}}.}}}}