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

The $\mathit q{}^{2}$ dependence is expected to be small providing no thresholds are nearby.

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

INSPIRE   JSON  (beta) PDGID:
S035MM
For a theoretical calculation [(${\mathit g}_{{{\mathit \tau}}}−$2)/2 = 117$~721(5){\times }10^{-8}$], see EIDELMAN 2007.
VALUE CL% DOCUMENT ID TECN  COMMENT
$\bf{-0.057\text{ to }0.024 }$ 95 1
AAD
2023BM
 ATLS ${{\mathit \gamma}}$ ${{\mathit \gamma}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$, ${}^{}\mathrm {Pb}−{}^{}\mathrm {Pb}$
• • We do not use the following data for averages, fits, limits, etc. • •
$-0.041$ ${}^{+0.012}_{-0.009}$ 2, 1
AAD
2023BM
 ATLS ${{\mathit \gamma}}$ ${{\mathit \gamma}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$, ${}^{}\mathrm {Pb}−{}^{}\mathrm {Pb}$
$0.001$ ${}^{+0.055}_{-0.089}$ 2, 3
TUMASYAN
2023AS
 CMS ${{\mathit \gamma}}$ ${{\mathit \gamma}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$, ${}^{}\mathrm {Pb}-{}^{}\mathrm {Pb}$
$-0.018$ $\pm0.017$ 4, 2
ABDALLAH
2004K
 DLPH ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$
$<0.107$ 95 5
ACHARD
2004G
 L3 ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$
$-0.007\text{ to }0.005 $ 95 6
GONZALEZ-SPRI..
2000
RVUE ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ and ${{\mathit W}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \nu}_{{{\tau}}}}$
$-0.052\text{ to }0.058 $ 95 7
ACCIARRI
1998E
 L3 1991--1995 LEP runs
$-0.068\text{ to }0.065 $ 95 8
ACKERSTAFF
1998N
 OPAL 1990--1995 LEP runs
$-0.004\text{ to }0.006 $ 95 9
ESCRIBANO
1997
RVUE ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ at LEP
$<0.01$ 95 10
ESCRIBANO
1993
RVUE ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ at LEP
$<0.12$ 90
GRIFOLS
1991
RVUE ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}}{{\mathit \gamma}}$ at LEP
$<0.023$ 95 11
SILVERMAN
1983
RVUE ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ at PETRA
1  AAD 2023BM measurement is derived from ${{\mathit \gamma}}$ ${{\mathit \gamma}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ total cross-section from 1.44 nb${}^{-1}$ LHC ${}^{}\mathrm {Pb}−{}^{}\mathrm {Pb}$ collisions at $\sqrt {{{\mathit S}_{{{NN}}}} }$ = 5.02 TeV. Authors report both the measured value and the corresponding 95$\%$ CL limit.
2  Measurement ill-suited for a standard average because its likelihood appears to be remarkably non-Gaussian and asymmetric according to the model-dependent extraction procedure and the reported 95$\%$ CL limits.
3  TUMASYAN 2023AS measurement is derived from ${{\mathit \gamma}}$ ${{\mathit \gamma}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ total cross-section from 404 ${{\mathit \mu}}$b${}^{-1}$ LHC ${}^{}\mathrm {Pb}-{}^{}\mathrm {Pb}$ collisions at $\sqrt {{{\mathit S}_{{{NN}}}} }$ = 5.02 TeV.
4  ABDALLAH 2004K measurement is derived from ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ total cross-section measurements at $\sqrt {s }$ between 183 and 208 GeV. In addition to the measurement, the authors also quote 95$\%$ CL limits of $>$ -0.052 and $<$ 0.013.
5  ACHARD 2004G limit is derived from ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ total cross-section measurements at $\sqrt {s }$ between 189 and 206 GeV, and is on the absolute value of the magnetic moment anomaly.
6  GONZALEZ-SPRINBERG 2000 use data on tau lepton production at LEP1, SLC, and LEP2, and data from colliders and LEP2 to determine limits. Assume imaginary component is zero.
7  ACCIARRI 1998E use ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}{{\mathit \gamma}}$ events. In addition to the limits, the authors also quote a value of $0.004$ $\pm0.027$ $\pm0.023$.
8  ACKERSTAFF 1998N use ${{\mathit Z}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}{{\mathit \gamma}}$ events. The limit applies to an average of the form factor for off-shell ${{\mathit \tau}}$'s having $\mathit p{}^{2}$ ranging from ${{\mathit m}^{2}}_{{{\mathit \tau}}}$ to ($\mathit M_{{{\mathit Z}}}-{\mathit m}_{{{\mathit \tau}}}){}^{2}$.
9  ESCRIBANO 1997 use preliminary experimental results.
10  ESCRIBANO 1993 limit derived from $\Gamma\mathrm {({{\mathit Z}} \rightarrow {{\mathit \tau}^{+}} {{\mathit \tau}^{-}})}$, and is on the absolute value of the magnetic moment anomaly.
11  SILVERMAN 1983 limit is derived from ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \tau}^{+}}{{\mathit \tau}^{-}}$ total cross-section measurements for $\mathit q{}^{2}$ up to (37 GeV)${}^{2}$.
References