Light Boson (${{\mathit X}^{0}}$ ) Search in Nonresonant ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Annihilation at Rest

INSPIRE  
Limits are for the ratio of ${{\mathit n}}{{\mathit \gamma}}{+}$ ${{\mathit X}^{0}}$ production relative to ${{\mathit \gamma}}{{\mathit \gamma}}$ .
VALUE ($ 10^{-6} $) CL% DOCUMENT ID TECN  COMMENT
• • We do not use the following data for averages, fits, limits, etc. • •
$<4.2$ 90 1
MITSUI
1996
CNTR ${{\mathit \gamma}}{{\mathit X}^{0}}$
$<4$ 68 2
SKALSEY
1995
CNTR ${{\mathit \gamma}}{{\mathit X}^{0}}$
$<40$ 68 3
SKALSEY
1995
RVUE ${{\mathit \gamma}}{{\mathit X}^{0}}$
$<0.18$ 90 4
ADACHI
1994
CNTR ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit X}^{0}}$ , ${{\mathit X}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
$<0.26$ 90 5
ADACHI
1994
CNTR ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit X}^{0}}$ , ${{\mathit X}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
$<0.33$ 90 6
ADACHI
1994
CNTR ${{\mathit \gamma}}{{\mathit X}^{0}}$ , ${{\mathit X}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$
1  MITSUI 1996 looked for a monochromatic ${{\mathit \gamma}}$ . The bound applies for a vector ${{\mathit X}^{0}}$ with $\mathit C=-1$ and ${\mathit m}_{{{\mathit X}^{0}}}<$200 keV. They derive an upper bound on ${{\mathit e}}{{\mathit e}}{{\mathit X}^{0}}$ coupling and hence on the branching ratio B( $\mathit o$-Ps $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit X}^{0}}$ )$<6.2 \times 10^{-6}$. The bounds weaken for heavier ${{\mathit X}^{0}}$ .
2  SKALSEY 1995 looked for a monochromatic ${{\mathit \gamma}}$ without an accompanying ${{\mathit \gamma}}$ in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ annihilation. The bound applies for scalar and vector ${{\mathit X}^{0}}$ with $\mathit C$ = $-1$ and ${\mathit m}_{{{\mathit X}^{0}}}$ = keV.
3  SKALSEY 1995 reinterpreted the bound on ${{\mathit \gamma}}{{\mathit A}^{0}}$ decay of $\mathit o$-Ps by ASAI 1991 where 3$\%$ of delayed annihilations are not from ${}^{3}\!{\mathit S}_{1}$ states. The bound applies for scalar and vector ${{\mathit X}^{0}}$ with $\mathit C$ = $-1$ and ${\mathit m}_{{{\mathit X}^{0}}}$ = $0 - 800$ keV.
4  ADACHI 1994 looked for a peak in the ${{\mathit \gamma}}{{\mathit \gamma}}$ invariant mass distribution in ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$ production from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ annihilation. The bound applies for ${\mathit m}_{{{\mathit X}^{0}}}$ = $70 - 800$ keV.
5  ADACHI 1994 looked for a peak in the missing-mass mass distribution in ${{\mathit \gamma}}{{\mathit \gamma}}$ channel, using ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$ production from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ annihilation. The bound applies for ${\mathit m}_{{{\mathit X}^{0}}}$ $<$800 keV.
6  ADACHI 1994 looked for a peak in the missing mass distribution in ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$ channel, using ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$ production from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ annihilation. The bound applies for ${\mathit m}_{{{\mathit X}^{0}}}$ = $200 - 900$ keV.
References:
MITSUI 1996
EPL 33 111 Limit on an Exotic Three Body Decay of Orthopositronium
SKALSEY 1995
PR D51 6292 Search for Exotic Decays from Low-Energy ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ Direct Annihilation
ADACHI 1994
PR A49 3201 Precise Measurements of ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ Annihilation at Rest into Four Photons and the Search for Exotic Particles