¹ See however KLOET 1996 who fit ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ only and find waves only up to $\mathit J = 3$ to be important but not significantly resonant.

² $\mathit I(\mathit J{}^{P}) = 1(1{}^{-})$ from simultaneous analysis of ${{\mathit p}}$ ${{\overline{\mathit p}}}$ $\rightarrow$ ${{\mathit \pi}^{-}}{{\mathit \pi}^{+}}$ and ${{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ .

References:

HASAN

1994

PL B334 215

Amplitudes for ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}}{{\mathit \pi}}$ from 0.36 to 2.5 ${\mathrm {GeV/}}\mathit c$

OAKDEN

1994

NP A574 731

Amplitude Analysis of Data on ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}}{{\mathit \pi}}$ at Low Energy

MARTIN

1980B

NP B176 355

Structures in ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}}{{\mathit \pi}}$

MARTIN

1980C

NP B169 216

Exploration of the ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}}{{\mathit \pi}}$ Channel in the Resonance Region