# ${{\boldsymbol A}^{0}}$ (Axion) Limits from Its Electron Coupling INSPIRE search

Limits are for $\tau\mathrm {( {{\mathit A}^{0}} \rightarrow {{\mathit e}^{+}} {{\mathit e}^{-}} )}$.
VALUE (s) CL% DOCUMENT ID TECN  COMMENT
• • • We do not use the following data for averages, fits, limits, etc. • • •
$\text{none } 4 \times 10^{-16} - 4.5 \times 10^{-12}$ 90 1
 1991
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$ )
2
 1990
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$ )
3
 1988
CALO ${{\mathit A}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$ or 2 ${{\mathit \gamma}}$
4
 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 5
 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 6
 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 7
 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 8
 1986
BDMP ${{\mathit e}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit e}}{{\mathit A}^{0}}{{\mathit N}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit e}}{{\mathit e}}$ )
1  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).
2  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).
3  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.
4  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$\%$).
5  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.
6  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.
7  ${\mathit m}_{{{\mathit A}^{0}}}$ = 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.
8  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:
 BROSS 1991
PRL 67 2942 A Search for Short Lived Particles Produced in an Electron Beam Dump
 GUO 1990
PR D41 2924 Improved Limit on Axion Production in 800 GeV Hadronic Showers
 BJORKEN 1988
PR D38 3375 Search for Neutral Metastable Penetrating Particles Produced in the SLAC Beam Dump
 BLINOV 1988
SJNP 47 563 Limit on the Two Photon Width of the Particles with the Mass of 1.8 ${\mathrm {MeV}}/\mathit c{}^{2}$
 RIORDAN 1987
PRL 59 755 Search for Short Lived Axions in an Electron Beam Dump Experiment
 BROWN 1986
PRL 57 2101 A New Limit on Axion Production in 800 GeV Hadronic Showers
 DAVIER 1986
PL B180 295 Search for Axionlike Particles in Electron Bremsstrahlung
 KONAKA 1986
PRL 57 659 Search for Neutral Particles in Electron Beam Dump Experiment