${{\mathit A}^{0}}$ (Axion) Limits from Its Electron Coupling

INSPIRE   PDGID:
S029AXE
Limits are for $\tau\mathrm {( {{\mathit A}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}})}$.
CL% DOCUMENT ID TECN  COMMENT
• • We do not use the following data for averages, fits, limits, etc. • •
1
ANDREEV
2021
NA64 ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ invisibles)
2
ANDREEV
2021B
 NA64 ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
$\text{none } 4 \times 10^{-16} - 4.5 \times 10^{-12}$ 90 3
BROSS
1991
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
4
GUO
1990
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
5
BJORKEN
1988
CALO ${{\mathit A}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ or 2 ${{\mathit \gamma}}$
6
BLINOV
1988
MD1 ${{\mathit e}}$ ${{\mathit e}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}{{\mathit A}^{0}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
$\text{none } 1 \times 10^{-14} - 1 \times 10^{-10}$ 90 7
RIORDAN
1987
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
$\text{none } 1 \times 10^{-14} - 1 \times 10^{-11}$ 90 8
BROWN
1986
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
$\text{none } 6 \times 10^{-14} - 9 \times 10^{-11}$ 95 9
DAVIER
1986
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
$\text{none } 3 \times 10^{-13} - 1 \times 10^{-7}$ 90 10
KONAKA
1986
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$)
1  ANDREEV 2021 look for invisible decays of axions coupled to electrons, and set limits on $\mathit g_{{{\mathit A}} {{\mathit e}} {{\mathit e}}}$ $<$ $4.6 \times 10^{-6} - 3.1 \times 10^{-3}$ for ${\mathit m}_{{{\mathit A}^{0}}}$ = $10^{-3} - 1$ GeV. This limits the axion contribution to the electron $\mathit g−$2 to an order of magnitude less than the current experimental uncertainty. See their Figs. 3 and 4 for mass-dependent limits.
2  ANDREEV 2021B set limits on $\mathit g_{{{\mathit A}} {{\mathit e}} {{\mathit e}}}$ in the range of $6.3 \times 10^{-6} - 1.6 \times 10^{-3}$ for ${\mathit m}_{{{\mathit A}^{0}}}$ = $2 - 17$ MeV at 90$\%$ CL. This excludes $6.6 \times 10^{-5}$ $<$ $\mathit g_{{{\mathit A}} {{\mathit e}} {{\mathit e}}}$ $<$ $1 \times 10^{-4}$ at ${\mathit m}_{{{\mathit A}^{0}}}$ = 16.7 MeV corresponding to the ATOMKI anomaly. See their Fig. 2 for mass-dependent limits.
3  The listed BROSS 1991 limit is for ${\mathit m}_{{{\mathit A}^{0}}}$ = $1.14~$MeV. B( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$) =$~$1 assumed. Excluded domain in the ${\mathit \tau}_{{{\mathit A}^{0}}}-{\mathit m}_{{{\mathit A}^{0}}}$ plane extends up to ${\mathit m}_{{{\mathit A}^{0}}}$ $\approx{}~$7 MeV (see Fig.$~$5). Combining with electron $\mathit g~-~2$ constraint, axions coupling only to ${{\mathit e}^{+}}{{\mathit e}^{-}}$ ruled out for ${\mathit m}_{{{\mathit A}^{0}}}$ $<~4.8$ MeV (90$\%$ CL).
4  GUO 1990 use the same apparatus as BROWN 1986 and improve the previous limit in the shorter lifetime region. Combined with $\mathit g~-~$2 constraint, axions coupling only to ${{\mathit e}^{+}}{{\mathit e}^{-}}$ are ruled out for ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ $2.7$ MeV (90$\%$ CL).
5  BJORKEN 1988 reports limits on axion parameters (${{\mathit f}_{{{A}}}}$, ${{\mathit m}_{{{A}}}}$, ${{\mathit \tau}_{{{A}}}}$) for ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 200 MeV from electron beam-dump experiment with production via Primakoff photoproduction, bremsstrahlung from electrons, and resonant annihilation of positrons on atomic electrons.
6  BLINOV 1988 assume zero spin, $\mathit m$ = $1.8$ MeV and lifetime $<$ $5 \times 10^{-12}~$s and find $\Gamma\mathrm {( {{\mathit A}^{0}} \rightarrow {{\mathit \gamma}} {{\mathit \gamma}})}$B( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$) $<$ 2 eV (CL=90$\%$).
7  Assumes ${{\mathit A}^{0}}{{\mathit \gamma}}{{\mathit \gamma}}$ coupling is small and hence Primakoff production is small. Their figure 2 shows limits on axions for ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 15 MeV.
8  Uses electrons in hadronic showers from an incident 800 GeV proton beam. Limits for ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 15 MeV are shown in their figure 3.
9  ${\mathit m}_{{{\mathit A}^{0}}}$ = 1.8 MeV assumed. The excluded domain in the ${\mathit \tau}_{{{\mathit A}^{0}}}−{\mathit m}_{{{\mathit A}^{0}}}$ plane extends up to ${\mathit m}_{{{\mathit A}^{0}}}$ $\approx{}$ 14 MeV, see their figure 4.
10  The limits are obtained from their figure 3. Also given is the limit on the ${{\mathit A}^{0}}{{\mathit \gamma}}{{\mathit \gamma}}−{{\mathit A}^{0}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ coupling plane by assuming Primakoff production.
References