#### Search for ${{\mathit X}^{0}}$ Resonance in ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit X}^{0}}{{\mathit \gamma}}$

VALUE (GeV) DOCUMENT ID TECN  COMMENT
• • We do not use the following data for averages, fits, limits, etc. • •
1
 2003 D
OPAL ${{\mathit X}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
2
 2000 Z
DLPH ${{\mathit X}^{0}}$ decaying invisibly
3
 1996 C
DLPH ${{\mathit X}^{0}}$ decaying invisibly
 1 ABBIENDI 2003D measure the ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \gamma}}$ cross section at $\sqrt {\mathit s }=181 - 209$ GeV. The upper bound on the production cross section, $\sigma\mathrm {( {{\mathit e}^{+}} {{\mathit e}^{-}} \rightarrow {{\mathit X}^{0}} {{\mathit \gamma}} )}$ times the branching ratio for ${{\mathit X}^{0}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ , is less than $0.03~$pb at 95$\%$CL for ${{\mathit X}^{0}}$ masses between 20 and 180 GeV. See their Fig.$~$9b for the limits in the mass-cross section plane.
 2 ABREU 2000Z is from the single photon cross section at $\sqrt {\mathit s }$=183, 189$~$GeV. The production cross section upper limit is less than $0.3~$pb for ${{\mathit X}^{0}}$ mass between 40 and 160 GeV. See their Fig.$~$4 for the limit in mass-cross section plane.
 3 ADAM 1996C is from the single photon production cross at $\sqrt {\mathit s }$=130, 136 GeV. The upper bound is less than 3$~$pb for ${{\mathit X}^{0}}$ masses between 60 and 130 GeV. See their Fig.$~$5 for the exact bound on the cross section ${\mathit \sigma (}$ ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit X}^{0}}{)}$.
References:
 ABBIENDI 2003D
EPJ C26 331 Multiphoton Production in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at $\sqrt {s }$ = 181 to 209 GeV
 ABREU 2000Z
EPJ C17 53 Photon Events with Missing Energy at $\sqrt {s }$ = 183 to 189-GeV
PL B380 471 Search for Anomalous Production of Single Photons at $\sqrt {s }$ = 130 and 136 GeV