# ${{\boldsymbol A}^{0}}$ (Axion) Searches in Positronium Decays INSPIRE search

Decay or transition of positronium. Limits are for branching ratio.
VALUE CL% DOCUMENT ID TECN  COMMENT
• • • We do not use the following data for averages, fits, limits, etc. • • •
$<4.4 \times 10^{-5}$ 90 1
 2002
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit \gamma}}{{\mathit X}_{{1}}}{{\mathit X}_{{2}}}$ , ${\mathit m}_{{{\mathit X}_{{1}}}}+{\mathit m}_{{{\mathit X}_{{2}}}}{}\leq{}$900 keV
$<2 \times 10^{-4}$ 90
 1995
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ ${\mathit m}_{{{\mathit A}^{0}}}=850 - 1013$ keV
$<3.0 \times 10^{-4}$ 90 2
 1994
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ ${\mathit m}_{{{\mathit A}^{0}}}=30 - 500$ keV
$<2.8 \times 10^{-5}$ 90 3
 1991
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ ( ${{\mathit A}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ ), ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 30 keV
$<1.1 \times 10^{-6}$ 90 4
 1991
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ , ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 800 keV
$<3.8 \times 10^{-4}$ 90
 1990
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ , ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 30 keV
$<(1 - 5){\times }\text{ 10^}{-4}$ 95 5
 1990
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ , ${\mathit m}_{{{\mathit A}^{0}}}$ = $300-900$ keV
$<6.4 \times 10^{-5}$ 90 6
 1989
CNTR $\mathit o$-Ps $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ , ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 30 keV
7
 1985
CNTR Ortho-positronium
8
 1983
CNTR Ortho-positronium
1  BADERTSCHER 2002 looked for a three-body decay of ortho-positronium into a photon and two penetrating (neutral or milli-charged) particles.
2  The ASAI 1994 limit is based on inclusive photon spectrum and is independent of ${{\mathit A}^{0}}$ decay modes.
3  The AKOPYAN 1991 limit applies for a short-lived ${{\mathit A}^{0}}$ with ${\mathit \tau}_{{{\mathit A}^{0}}}$ $<10^{-13}{\mathit m}_{{{\mathit A}^{0}}}$ [keV]$~$s.
4  ASAI 1991 limit translates to $\mathit g{}^{2}_{ {{\mathit A}^{0}} {{\mathit e}^{+}} {{\mathit e}^{-}} }/4\pi$ $<$ $1.1 \times 10^{-11}$ (90$\%$ CL) for ${\mathit m}_{{{\mathit A}^{0}}}$ $<$ 800 keV.
5  The TSUCHIAKI 1990 limit is based on inclusive photon spectrum and is independent of ${{\mathit A}^{0}}$ decay modes.
6  ORITO 1989 limit translates to $\mathit g{}^{2}_{ {{\mathit A}^{0}} {{\mathit e}} {{\mathit e}} }/4\pi$ $<$ $6.2 \times 10^{-10}$. Somewhat more sensitive limits are obtained for larger ${\mathit m}_{{{\mathit A}^{0}}}$: $\mathit B$ $<$ $7.6 \times 10^{-6}$ at 100 keV.
7  AMALDI 1985 set limits B( ${{\mathit A}^{0}}{{\mathit \gamma}}$ ) $/$ B( ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$ ) $<$ (1$-5){\times }10^{-6}$ for ${\mathit m}_{{{\mathit A}^{0}}}$ = 900$-$100 keV which are about 1/10 of the CARBONI 1983 limits.
8  CARBONI 1983 looked for orthopositronium $\rightarrow$ ${{\mathit A}^{0}}{{\mathit \gamma}}$ . Set limit for ${{\mathit A}^{0}}$ electron coupling squared, $\mathit g$( ${{\mathit e}}{{\mathit e}}{{\mathit A}^{0}}$ )${}^{2}/(4{}{{\mathit \pi}}$) $<6. \times 10^{-10}-7. \times 10^{-9}$ for ${\mathit m}_{{{\mathit A}^{0}}}$ from 150$-$900 keV (CL = $99.7\%$). This is about 1/10 of the bound from $\mathit g−$2 experiments.
References:
PL B542 29 Search for an Exotic Three-body Decay of Orthopositronium
 MAENO 1995
PL B351 574 A Search for Massive Neutral Bosons in Orthopositronium Decay
 ASAI 1994
PL B323 90 Search for Shortlived Neutral Bosons in Orthopositronium Decay
 AKOPYAN 1991
PL B272 443 Search for a Light Shortlived Neutral Boson in Orthopositronium Decay
 ASAI 1991
PRL 66 2440 Search for Longlived Neutral Bosons in Orthopositronium Decay
 GNINENKO 1990
PL B237 287 A Search for a keV Pseudoscalar in the Two Body Decay of Orthopositronium
 TSUCHIAKI 1990
PL B236 81 Search for Neutral Boson in Orthopositronium Decay
 ORITO 1989
PRL 63 597 New Limits on Exotic Two-Body Decay of Orthopositronium
 AMALDI 1985
PL 153B 444 New Limits on the Single ${{\mathit \gamma}}$ Decay of Orthopositronium
 CARBONI 1983
PL 123B 349 Limit on Exotic Two Body Decays of Ortopositronium