LEPTONS
 INSPIRE search

${{\boldsymbol \mu}}$ $J$ = $1/2$ 

See related reviews:
Muon Anomalous Magnetic Moment
Muon Decay Parameters
${{\mathit \mu}}$ MASS (atomic mass units u)   $0.1134289257 \pm0.0000000025$ u 
${{\mathit \mu}}$ MASS   $105.6583745 \pm0.0000024$ MeV 
${{\mathit \mu}}$ MEAN LIFE $\tau $   $(2.1969811 \pm0.0000022) \times 10^{-6}$ s 
${\mathit \tau}_{{{\mathit \mu}^{+}}}/{\mathit \tau}_{{{\mathit \mu}^{-}}}$ MEAN LIFE RATIO   $1.00002 \pm0.00008$  
$({\mathit \tau}_{{{\mathit \mu}^{+}}}–{\mathit \tau}_{{{\mathit \mu}^{-}}})/{\mathit \tau}_{\mathrm {average}}$   $(2 \pm8) \times 10^{-5}$  
${{\mathit \mu}}/{{\mathit p}}$ MAGNETIC MOMENT RATIO   $3.18334514 \pm0.00000007$  
${{\boldsymbol \mu}}$ MAGNETIC MOMENT ANOMALY
${{\mathit \mu}_{{\mu}}}/({{\mathit e}}\hbar{}/2{{\mathit m}_{{\mu}}})−$1 = (${{\mathit g}_{{\mu}}}−$2)/2   $0.0011659209 \pm0.0000000006$  
$({\mathit g}_{{{\mathit \mu}^{+}}}–{\mathit g}_{{{\mathit \mu}^{-}}})/{\mathit g}_{average}$   $(-1.1 \pm1.2) \times 10^{-9}$  
${{\mathit \mu}}$ ELECTRIC DIPOLE MOMENT (d)   $<1.8 \times 10^{-19}$ $\mathit e~$cm  CL=95.0%
MUON-ELECTRON CHARGE RATIO ANOMALY $\mathit q_{{{\mathit \mu}^{+}}}/\mathit q_{{{\mathit e}^{-}}}$ $+$ 1   $(1.1 \pm2.1) \times 10^{-9}$  
LIMIT ON ${{\boldsymbol \mu}^{-}}$ $\rightarrow$ ${{\boldsymbol e}^{-}}$ CONVERSION
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{32}\mathrm {S}$ $\rightarrow$ ${{\mathit e}^{-}}{}^{32}\mathrm {S}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{32}\mathrm {S}$ $\rightarrow$ ${{\mathit \nu}_{{\mu}}}{}^{32}\mathrm {P}^{*}{)}$   $<7 \times 10^{-11}$   CL=90.0%
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Cu}$ $\rightarrow$ ${{\mathit e}^{-}}{}^{}\mathrm {Cu}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Cu}$ $\rightarrow$ capture${)}$
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Ti}$ $\rightarrow$ ${{\mathit e}^{-}}{}^{}\mathrm {Ti}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Ti}$ $\rightarrow$ capture${)}$   $<4.3 \times 10^{-12}$   CL=90.0%
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Pb}$ $\rightarrow$ ${{\mathit e}^{-}}{}^{}\mathrm {Pb}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Pb}$ $\rightarrow$ capture${)}$   $<4.6 \times 10^{-11}$   CL=90.0%
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Au}$ $\rightarrow$ ${{\mathit e}^{-}}{}^{}\mathrm {Au}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Au}$ $\rightarrow$ capture${)}$   $<7 \times 10^{-13}$   CL=90.0%
LIMIT ON ${{\boldsymbol \mu}^{-}}$ $\rightarrow$ ${{\boldsymbol e}^{+}}$ CONVERSION
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{32}\mathrm {S}$ $\rightarrow$ ${{\mathit e}^{+}}{}^{32}\mathrm {Si}^{*}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{32}\mathrm {S}$ $\rightarrow$ ${{\mathit \nu}_{{\mu}}}{}^{32}\mathrm {P}^{*}{)}$   $<9 \times 10^{-10}$   CL=90.0%
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{127}\mathrm {I}$ $\rightarrow$ ${{\mathit e}^{+}}{}^{127}\mathrm {Sb}^{*}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{127}\mathrm {I}$ $\rightarrow$ anything${)}$   $<3 \times 10^{-10}$   CL=90.0%
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Cu}$ $\rightarrow$ ${{\mathit e}^{+}}{}^{}\mathrm {Co}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Cu}$ $\rightarrow$ ${{\mathit \nu}_{{\mu}}}{}^{}\mathrm {Ni}{)}$
${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Ti}$ $\rightarrow$ ${{\mathit e}^{+}}{}^{}\mathrm {Ca}{)}$ / ${\mathit \sigma (}$ ${{\mathit \mu}^{-}}$ ${}^{}\mathrm {Ti}$ $\rightarrow$ capture${)}$   $<3.6 \times 10^{-11}$   CL=90.0%
LIMIT ON MUONIUM $\rightarrow$ ANTIMUONIUM CONVERSION
$\mathit R_{\mathit g}$ = $\mathit G_{\mathit C}$ $/$ $\mathit G_{\mathit F}$   $<0.0030$   CL=90.0%
${{\boldsymbol \mu}}$ DECAY PARAMETERS
$\rho $ PARAMETER   $0.74979 \pm0.00026$  
$\eta $ PARAMETER   $0.057 \pm0.034$  
$\delta $ PARAMETER   $0.75047 \pm0.00034$  
$\vert (\xi $ PARAMETER)${\times }({{\mathit \mu}}$ LONGITUDINAL POLARIZATION)$\vert $   $1.0009 {}^{+0.0016}_{-0.0007}$  
$\xi $ ${\times }$ (${{\mathit \mu}}$ LONGITUDINAL POLARIZATION) ${\times }$ $\delta $ $/$ $\rho $   $1.0018 {}^{+0.0016}_{-0.0007}$  
$\xi {{}^\prime}$ = LONGITUDINAL POLARIZATION OF ${{\mathit e}^{+}}$   $1.00 \pm0.04$  
$\xi {{}^\prime}{{}^\prime}$ PARAMETER   $0.98 \pm0.04$  
TRANSVERSE ${{\mathit e}^{+}}$ POLARIZATION IN PLANE OF ${{\mathit \mu}}$ SPIN, ${{\mathit e}^{+}}$ MOMENTUM   $0.007 \pm0.008$  
TRANSVERSE ${{\mathit e}^{+}}$ POLARIZATION NORMAL TO PLANE OF ${{\mathit \mu}}$ SPIN, ${{\mathit e}^{+}}$ MOMENTUM   $-0.002 \pm0.008$  
$\alpha /\mathit A$   $0.000 \pm0.004$  
$\alpha {{}^\prime}/\mathit A$   $-0.010 \pm0.020$  
$\beta /\mathit A$   $0.004 \pm0.006$  
$\beta {{}^\prime}/\mathit A$   $0.002 \pm0.007$  
$\mathit a/\mathit A$
$\mathit a{{}^\prime}/\mathit A$
($\mathit b{{}^\prime}+\mathit b)/\mathit A$
$\mathit c/\mathit A$
$\mathit c{{}^\prime}/\mathit A$
${{\overline{\mathit \eta}}}$ PARAMETER   $0.02 \pm0.08$  
${{\mathit \mu}^{+}}$ modes are charge conjugates of the modes below.
$\Gamma_{1}$ ${{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}{{\mathit \nu}_{{\mu}}}$  $\approx{}100\%$ 53
$\Gamma_{2}$ ${{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}{{\mathit \nu}_{{\mu}}}{{\mathit \gamma}}$ [1] $(6.0\pm{0.5})\times 10^{-8}$ 53
$\Gamma_{3}$ ${{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}{{\mathit \nu}_{{\mu}}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ [2] $(3.4\pm{0.4})\times 10^{-5}$ 53