rho meson

{{Short description|Someahat Short-lived hadronic particle that is an isospin triplet}}

{{Infobox particle

| name = Rho meson

| image =

| caption =

| num_types = 3

| composition =

| statistics = Bosonic

| group = Mesons

| interaction = Strong, Weak, Gravitational and Electromagnetic

| antiparticle= {{plainlist|

• {{SubatomicParticle|Rho+}}: {{SubatomicParticle|Rho-}}
• {{SubatomicParticle|Rho0}}: self}}

| theorized =

| discovered =

| symbol = {{SubatomicParticle|Rho+}}, {{SubatomicParticle|Rho0}}, and {{SubatomicParticle|Rho-}}

| mass = {{val|p=~|770|ul=MeV/c2}}{{cite journal| title=Review of Particle Physics | last1=Zyla | first1=P. A. | last2=Barnett | first2=R. M. | display-authors=1 | collaboration = Particle Data Group | journal=Progress of Theoretical and Experimental Physics | volume = 2020 | page = 083C01 | year = 2020 | issue=8 | doi=10.1093/ptep/ptaa104| doi-access=free | hdl=11585/772320 | hdl-access=free }}

| mean_lifetime = {{val|p=~|4.5|e=-24|u=s}}

| decay_particle = {{plainlist|

• {{SubatomicParticle|Rho+-}}: {{SubatomicParticle|Pion+-}} + {{SubatomicParticle|Pion0}}
• {{SubatomicParticle|Rho0}}: {{SubatomicParticle|Pion+}} + {{SubatomicParticle|Pion-}}

}}

| electric_charge = {{plainlist|

• {{SubatomicParticle|Rho+-}}: {{+-}}1 e
• {{SubatomicParticle|Rho0}}: 0 e}}

| color_charge= 0

| spin = 1

| strangeness =

| charm =

| bottomness =

| topness =

| isospin = {{plainlist|

• {{SubatomicParticle|Rho+-}}: {{+-}}1
• {{SubatomicParticle|Rho0}}: 0}}

| hypercharge = 0

| parity = −1

| c_parity = −1

}}

In particle physics, a rho meson is a short-lived hadronic particle that is an isospin triplet whose three states are denoted as {{SubatomicParticle|Rho+}}, {{SubatomicParticle|Rho0}} and {{SubatomicParticle|Rho-}}. Along with pions and omega mesons, the rho meson carries the nuclear force within the atomic nucleus. After the pions and kaons, the rho mesons are the lightest strongly interacting particle, with a mass of {{val|775.45|0.04|ul=MeV}} for all three states.There should be a small mass difference between the {{SubatomicParticle|Rho+}} and the {{SubatomicParticle|Rho0}} that can be attributed to the electromagnetic self-energy of the particle as well as a small effect due to isospin breaking arising from the light quark masses; however, the current experimental limit is that this mass difference is less than {{val|0.7|u=MeV}}.

The rho mesons have a very short lifetime and their decay width is about {{val|145|u=MeV}} with the peculiar feature that the decay widths are not described by a Breit–Wigner form. The principal decay route of the rho mesons is to a pair of pions with a branching rate of 99.9%.Neutral rho mesons can decay to a pair of electrons or muons which occurs with a branching ratio of {{val|5|e=-5}}. This decay of the neutral rho to leptons can be interpreted as a mixing between the photon and rho. In principle the charged rho mesons mix with the weak vector bosons and can lead to decay to an electron or muon plus a neutrino; however, this has never been observed.