${{\mathit \mu}}$ MAGNETIC MOMENT ANOMALY

The parity-violating decay of muons in a storage ring is observed. The difference frequency $\omega _{\mathit a}$ between the muon spin precision and the orbital angular frequency (${{\mathit e}}/{\mathit m}_{{{\mathit \mu}}}\mathit c)\langle{}\mathit B\rangle{}$ is measured, as is the free proton NMR frequency $\omega _{{{\mathit p}}}$, thus determining the ratio $\mathit R=\omega _{\mathit a}/\omega _{{{\mathit p}}}$. Given the magnetic moment ratio $\lambda =\mu _{{{\mathit \mu}}}/\mu _{{{\mathit p}}}$ (from hyperfine structure in muonium), ($\mathit g−$2)/2 = $\mathit R/(\lambda −\mathit R$).

${{\mathit \mu}_{{{\mu}}}}/({{\mathit e}}\hbar{}/2{{\mathit m}_{{{\mu}}}})−$1 = (${{\mathit g}_{{{\mu}}}}−$2)/2

INSPIRE   PDGID:
S004MM
VALUE ($ 10^{-10} $) DOCUMENT ID TECN CHG  COMMENT
$11659205.9$ $\pm2.2$ 1
AGUILLARD
2023
MUG2 $\pm{}$ Combined FNAL and BNL values
• • We do not use the following data for averages, fits, limits, etc. • •
$11659205.5$ $\pm2.4$ 2
AGUILLARD
2023
MUG2 + Storage ring
$11659204.0$ $\pm5.4$
ABI
2021
MUG2 + Storage ring
$11659206.1$ $\pm4.1$ 3
ABI
2021
MUG2 $\pm{}$ Combined FNAL and BNL values
$11659208.0$ $\pm5.4$ $\pm3.3$
BENNETT
2006
MUG2 $\pm{}$ Average ${{\mathit \mu}^{+}}$ and ${{\mathit \mu}^{-}}$
$11659208$ $\pm6$
BENNETT
2004
MUG2 $\pm{}$ Average ${{\mathit \mu}^{+}}$ and ${{\mathit \mu}^{-}}$
$11659214$ $\pm8$ $\pm3$
BENNETT
2004
MUG2 - Storage ring
$11659203$ $\pm6$ $\pm5$
BENNETT
2004
MUG2 + Storage ring
$11659204$ $\pm7$ $\pm5$
BENNETT
2002
MUG2 + Storage ring
$11659202$ $\pm14$ $\pm6$
BROWN
2001
MUG2 + Storage ring
$11659191$ $\pm59$
BROWN
2000
MUG2 +
$11659100$ $\pm110$ 4
BAILEY
1979
CNTR + Storage ring
$11659360$ $\pm120$ 4
BAILEY
1979
CNTR - Storage ring
$11659230$ $\pm85$ 4
BAILEY
1979
CNTR $\pm{}$ Storage ring
$11620000$ $\pm5000$
CHARPAK
1962
CNTR +
1  AGUILLARD 2023 combined their value with the previous independent BNL measurement of BENNETT 2006.
2  This AGUILLARD 2023 value is the combination of all 2018, 2019 and 2020 data, including the ABI 2021 value. The new FNAL 2019 and 2020 data alone combined yield ($11659205.7$ $\pm2.5$) $ \times 10^{-10}$.
3  ABI 2021 combined their value with the previous independent BNL measurement of BENNETT 2006. ABI 2021 also report that the difference of this combination with the standard model value of ($11659181.0$ $\pm4.3$) $ \times 10^{-10}$ (AOYAMA 2020) has a significance of 4.2 ${{\mathit \sigma}}$.
4  BAILEY 1979 values recalculated by HUGHES 1999 using the COHEN 1987 ${{\mathit \mu}}/{{\mathit p}}$ magnetic moment. The improved MOHR 1999 value does not change the result.
References