Article citationsMore>>
Devons, S., Kozlowski, T., Nemethy, P., Shapiro, S., Horwitz, N., Kalogeropoulos, T., et al. (1971) Observation of →2π0 at Rest: Evidence Concerning S-State Annihilation. Physical Review Letters, 27, 1614-1617.
https://doi.org/10.1103/physrevlett.27.1614
has been cited by the following article:
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TITLE:
Evidence for a Second Neutral Pion
AUTHORS:
Walton A. Perkins
KEYWORDS:
Second Neutral Pion, Antiproton-Proton Annihilation
JOURNAL NAME:
Journal of High Energy Physics, Gravitation and Cosmology,
Vol.11 No.4,
September
23,
2025
ABSTRACT: Evidence suggests the existence of a second neutral pion based on: (1) the anomalous branching ratios in the reactions
p
¯
p→ππ
and
p
¯
d→ππN
, and (2) the 1960s findings of Tsai-Chü et al. regarding antinucleon annihilation stars in emulsions. The anomaly in (1) disappears if the two neutral pions in the reactions
p
¯
p→
π
0
π
0
and
p
¯
d→
π
0
π
0
n
are not identical. Tsai-Chü et al. observed a second neutral pion that “decays more rapidly into electron pairs with larger opening angles and more frequently into double pairs.” One antineutron annihilation event produced three neutral particles, each with a mass of 135 ± 14 MeV, decaying into four electrons with significantly wider opening angles than those of the internal conversion electrons observed in
π
0
decays. The larger opening angles and higher frequency of double pair production could be caused by neutral pions with such a short lifetime that they decay into photon pairs before they can leave the annihilation nucleus (e.g., Ag) of the emulsion. We discuss several methods for searching for a second neutral pion.