5
From solution B of amplitude analysis of data on ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}}{{\mathit \pi}}$. 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.
High-Statistics Study of Neutral-Pion Pair Production in Two-Photon Collisions
BINON
2005
PAN 68 960
Investigation of the ${{\mathit \eta}}{{\mathit \eta}}$ System in ${{\mathit \pi}^{-}}{{\mathit p}}$ Interactions at a Momentum of 32.5 GeV/$\mathit c$ at the GAMS-4$\pi $ Spectrometer
ABE
2004
EPJ C32 323
Measurement of ${{\mathit K}^{+}}{{\mathit K}^{-}}$ Production in Two Photon Collisions in the Resonant Mass Region
A Spin Analysis of the 4${{\mathit \pi}}$ Channels Produced in Central ${{\mathit p}}$ ${{\mathit p}}$ Interactions at 450 ${\mathrm {GeV/}}\mathit c$
ANISOVICH
1999B
PL B449 154
Observation of ${{\mathit f}_{{{0}}}{(1770)}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \eta}}$ in ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \eta}}{{\mathit \pi}^{0}}$ Reactions from 600 to 1200 ${\mathrm {MeV}}/\mathit c$
BARBERIS
1997B
PL B413 217
A Study of the Centrally Produced ${{\mathit \pi}^{+}}$ ${{\mathit \pi}^{-}}$ ${{\mathit \pi}^{+}}$ ${{\mathit \pi}^{-}}$ Channel in ${{\mathit p}}$ ${{\mathit p}}$ Interactions at 450 ${\mathrm {GeV/}}\mathit c$
ANTINORI
1995
PL B353 589
A Further Study of the Centrally Produced ${{\mathit \pi}^{+}}$ ${{\mathit \pi}^{-}}$ and ${{\mathit \pi}^{+}}$ ${{\mathit \pi}^{-}}$ ${{\mathit \pi}^{+}}$ ${{\mathit \pi}^{-}}$ Channels in ${{\mathit p}}$ ${{\mathit p}}$ Interactions at 300 and 450 ${\mathrm {GeV/}}\mathit c$
OAKDEN
1994
NP A574 731
Amplitude Analysis of Data on ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}}{{\mathit \pi}}$ at Low Energy