${{\boldsymbol \eta}}$ $\boldsymbol C$-NONCONSERVING DECAY PARAMETERS

${{\boldsymbol \pi}^{+}}{{\boldsymbol \pi}^{-}}{{\boldsymbol \gamma}}$ PARAMETER $\beta $ (${\boldsymbol D}{\mathrm -wave}$) INSPIRE search

Sensitive to a ${\mathit D}{\mathrm -wave}$ contribution: $\mathit dN/\mathit d$cos $\theta $ = sin$^2\theta $ ${}$ (1 + $\beta $ ${}$ cos $^2\theta $).
VALUE EVTS DOCUMENT ID TECN
$\bf{ -0.02 \pm0.07}$ OUR AVERAGE  Error includes scale factor of 1.3.
$0.11$ $\pm0.11$ 35k
JANE
1974B
 OSPK
$-0.060$ $\pm0.065$ 7250
GORMLEY
1970
WIRE
• • • We do not use the following data for averages, fits, limits, etc. • • •
$0.12$ $\pm0.06$ 1
THALER
1972
ASPK
1  The authors don't believe this indicates ${\mathit D}{\mathrm -wave}$ because the dependence of $\beta $ on the ${{\mathit \gamma}}$ energy is inconsistent with the theoretical prediction. A cos $^2\theta $ dependence can also come from $\mathit P$- and ${\mathit F}{\mathrm -wave}$ interference.
  Conservation Laws:
CHARGE CONJUGATION ($\mathit C$) INVARIANCE
  References:
JANE 1974B
PL 48B 265 Measurement of the Charge Asymmetry in the Decay ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$
THALER 1972
PRL 29 313 Charge Asymmetry in the Decay ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$
GORMLEY 1970
PR D2 501 Experimental Determination of the Dalitz-Plot Distribution of the Decays ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{0}}$ and ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$ , and the Branching ratio ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$ $/$ ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{0}}$