Editing Elementary particle (section)

=== Fundamental fermions ===
{{Main|Fermion}}

The 12&nbsp;fundamental fermions are divided into 3&nbsp;[[generation (particle physics)|generations]] of 4&nbsp;particles each. Half of the fermions are [[lepton]]s, three of which have an electric charge of −1&nbsp;''e'', called the electron ({{Subatomic particle|electron-}}), the [[muon]] ({{Subatomic particle|muon-}}), and the [[tau (particle)|tau]] ({{Subatomic particle|tau-}}); the other three leptons are [[neutrino]]s ({{Subatomic particle|electron neutrino}}, {{Subatomic particle|muon neutrino}}, {{Subatomic particle|tau neutrino}}), which are the only elementary fermions with neither electric nor [[color charge]]. The remaining six particles are [[quark]]s (discussed below).

==== Generations ====
{| class="wikitable"  style="text-align:center;"
|+ Particle generations
|-
!colspan="6"| [[Lepton]]s
|-
|colspan="2"| ''First generation''
|colspan="2"| ''Second generation''
|colspan="2"| ''Third generation''
|-
|''Name'' || ''Symbol'' || ''Name'' || ''Symbol'' || ''Name'' || ''Symbol''
|-
| [[electron]] || {{Subatomic particle|electron-}} || [[muon]] || {{math|{{Subatomic particle|muon-}}}} || [[tau (particle)|tau]] || {{math|{{Subatomic particle|tau-}}}}
|-
| [[electron neutrino]] || {{math|{{Subatomic particle|electron neutrino}}}} || [[muon neutrino]]|| {{math|{{Subatomic particle|Muon neutrino}}}} || [[tau neutrino]] || {{math|{{Subatomic particle|Tau neutrino}}}}
|-
!colspan="6"| [[Quark]]s
|-
|colspan="2"| ''First generation''
|colspan="2"| ''Second generation''
|colspan="2"| ''Third generation''
|-
| [[up quark]] || {{Subatomic particle|Up quark}} || [[charm quark]] || c || [[top quark]] || {{Subatomic particle|Top quark}}
|-
| [[down quark]] || {{Subatomic particle|Down quark}} || [[strange quark]] || {{Subatomic particle|Strange quark}} || [[bottom quark]]|| {{Subatomic particle|Bottom quark}}
|}

==== Mass ====
The following table lists current measured masses and mass estimates for all the fermions, using the same scale of measure: [[Electronvolt|millions of electron-volts]] relative to square of light speed (MeV/''c''<sup>2</sup>). For example, the most accurately known quark mass is of the top quark ({{Subatomic particle|top quark}}) at {{val|172.7|ul=GeV/c2}}, estimated using the [[on-shell scheme]].

{| class="wikitable" style="margin:0 0 1em 1em;"
|+ Current values for elementary fermion masses
|-
! Particle symbol
! Particle name
! Mass value
! Quark mass estimation scheme (point)
|-
| {{math|{{Subatomic particle|electron neutrino}}}}, {{math|{{Subatomic particle|muon neutrino}}}}, {{math|{{Subatomic particle|tauon neutrino}}}}
| [[Neutrino]]<br />(any&nbsp;type)
| style="text-align:right;" | < {{val|2|ul=eV/c2}}<ref>{{cite journal |last1=Tanabashi |first1=M. |last2=Hagiwara |first2=K. |last3=Hikasa |first3=K. |last4=Nakamura |first4=K. |last5=Sumino |first5=Y. |last6=Takahashi |first6=F. |last7=Tanaka |first7=J. |last8=Agashe |first8=K. |last9=Aielli |first9=G. |last10=Amsler |first10=C. |display-authors=6 |collaboration=Particle Data Group |title=Review of Particle Physics |journal=[[Physical Review D]] |volume=98 |issue=3 |date=2018-08-17 |page=030001 |df=dmy-all |doi=10.1103/physrevd.98.030001 |bibcode=2018PhRvD..98c0001T |pmid=10020536 |doi-access=free|hdl=10044/1/68623 |hdl-access=free }}</ref>
|
|-
| {{Subatomic particle|electron}}
| [[electron]]
| style="text-align:right;" | {{val|0.511|ul=MeV/c2}}
|
|-
| {{Subatomic particle|up quark}}
| [[up quark]]
| style="text-align:right;" | {{val|1.9|ul=MeV/c2}}
| [[MSbar scheme]] ({{mvar|μ}}<sub>{{overline|MS}}</sub> = {{val|2|u=GeV}})
|-
| {{Subatomic particle|down quark}}
| [[down quark]]
| style="text-align:right;" | {{val|4.4|ul=MeV/c2}}
| [[MSbar scheme]] ({{mvar|μ}}<sub>{{overline|MS}}</sub> = {{val|2|u=GeV}})
|-
| {{Subatomic particle|strange quark}}
| [[strange quark]]
| style="text-align:right;" | {{val|87|u=MeV/c2}}
| [[MSbar scheme]] ({{mvar|μ}}<sub>{{overline|MS}}</sub> = {{val|2|u=GeV}})
|-
| {{math|{{Subatomic particle|muon}}}}
| [[muon]]<br />([[mu lepton]])
| style="text-align:right;" | {{val|105.7|ul=MeV/c2}}
|
|-
| {{Subatomic particle|charm quark}}
| [[charm quark]]
| style="text-align:right;" | {{val|1320|ul=MeV/c2}}
| [[MSbar scheme]] ({{mvar|μ}}<sub>{{overline|MS}}</sub> = {{mvar|m}}<sub>c</sub>)
|-
| {{math|{{Subatomic particle|tau}}}}
| [[tauon]] ([[tau&nbsp;lepton]])
| style="text-align:right;" | {{val|1780|ul=MeV/c2}}
|
|-
| {{Subatomic particle|bottom quark}}
| [[bottom quark]]
| style="text-align:right;" | {{val|4240|ul=MeV/c2}}
| [[MSbar scheme]] ({{mvar|μ}}<sub>{{overline|MS}}</sub> = {{mvar|m}}<sub>b</sub>)
|-
| {{Subatomic particle|top quark}}
| [[top quark]]
| style="text-align:right;" | {{val|172700|ul=MeV/c2}}
| [[On-shell scheme]]
|}

Estimates of the values of quark masses depend on the version of [[quantum chromodynamics]] used to describe quark interactions. Quarks are always confined in an envelope of [[gluon]]s that confer vastly greater mass to the [[meson]]s and [[baryon]]s where quarks occur, so values for quark masses cannot be measured directly. Since their masses are so small compared to the effective mass of the surrounding gluons, slight differences in the calculation make large differences in the masses.

==== Antiparticles ====
{{Main|Antimatter}}

There are also 12&nbsp;fundamental fermionic antiparticles that correspond to these 12&nbsp;particles. For example, the [[antielectron]] (positron) {{Subatomic particle|antielectron}} is the electron's antiparticle and has an electric charge of +1&nbsp;''e''.

{| class="wikitable"  style="text-align:center;"
|+ Particle generations
|-
!colspan="6"| [[Lepton|Antileptons]]
|-
|colspan="2"| ''First generation''
|colspan="2"| ''Second generation''
|colspan="2"| ''Third generation''
|-
|''Name'' || ''Symbol'' || ''Name'' || ''Symbol'' || ''Name'' || ''Symbol''
|-
| [[positron]] || {{Subatomic particle|antielectron}} || [[antimuon]] || {{math|{{Subatomic particle|antimuon}}}} || [[antitau]] || {{math|{{Subatomic particle|antitau}}}}
|-
| [[electron antineutrino]] || {{math|{{Subatomic particle|electron antineutrino}}}} || [[muon antineutrino]]|| {{math|{{Subatomic particle|Muon antineutrino}}}} || [[tau antineutrino]] || {{math|{{Subatomic particle|Tau antineutrino}}}}
|-
!colspan="6"| [[Quark|Antiquarks]]
|-
|colspan="2"| ''First generation''
|colspan="2"| ''Second generation''
|colspan="2"| ''Third generation''
|-
| [[up antiquark]] || {{Subatomic particle|Up antiquark}} || [[charm antiquark]] || {{Subatomic particle|Charm antiquark}} || [[top antiquark]] || {{Subatomic particle|Top antiquark}}
|-
| [[down antiquark]] || {{Subatomic particle|Down antiquark}} || [[strange antiquark]] || {{Subatomic particle|Strange antiquark}}  ||  [[bottom antiquark]]|| {{Subatomic particle|Bottom antiquark}}
|}

==== Quarks ====
{{Main|Quark}}
Isolated quarks and antiquarks have never been detected, a fact explained by [[Colour confinement|confinement]]. Every quark carries one of three [[color charge]]s of the [[strong interaction]]; antiquarks similarly carry anticolor. Color-charged particles interact via [[gluon]] exchange in the same way that charged particles interact via [[photon]] exchange. Gluons are themselves color-charged, however, resulting in an amplification of the strong force as color-charged particles are separated. Unlike the [[electromagnetism|electromagnetic force]], which diminishes as charged particles separate, color-charged particles feel increasing force.

Nonetheless, color-charged particles may combine to form color neutral [[composite particle]]s called [[hadron]]s. A quark may pair up with an antiquark: the quark has a color and the antiquark has the corresponding anticolor. The color and anticolor cancel out, forming a color neutral [[meson]]. Alternatively, three quarks can exist together, one quark being "red", another "blue", another "green". These three colored quarks together form a color-neutral [[baryon]]. Symmetrically, three antiquarks with the colors "antired", "antiblue" and "antigreen" can form a color-neutral [[antibaryon]].

Quarks also carry fractional [[electric charge]]s, but, since they are confined within hadrons whose charges are all integral, fractional charges have never been isolated. Note that quarks have electric charges of either {{small|{{sfrac|+|2|3}}}}&nbsp;''e'' or {{small|{{sfrac|−|1|3}}}}&nbsp;''e'', whereas antiquarks have corresponding electric charges of either {{small|{{sfrac|−|2|3}}}}&nbsp;''e'' or&nbsp;{{small|{{sfrac|+|1|3}}}}&nbsp;''e''.

Evidence for the existence of quarks comes from [[deep inelastic scattering]]: firing [[electron]]s at [[atomic nucleus|nuclei]] to determine the distribution of charge within [[nucleon]]s (which are baryons). If the charge is uniform, the [[electric field]] around the proton should be uniform and the electron should scatter elastically. Low-energy electrons do scatter in this way, but, above a particular energy, the protons deflect some electrons through large angles. The recoiling electron has much less energy and a [[jet (particle physics)|jet of particles]] is emitted. This inelastic scattering suggests that the charge in the proton is not uniform but split among smaller charged particles: quarks.