#### ${{\boldsymbol \eta}}{{\boldsymbol \pi}}$ MODE

VALUE (MeV) EVTS DOCUMENT ID TECN CHG  COMMENT
 $\bf{ 1317.7 \pm1.4}$ OUR AVERAGE
$1308$ $\pm9$
 2000 H
450 ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}_{{f}}}{{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit p}_{{s}}}$
$1316$ $\pm9$
 2000 H
450 ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \Delta}_{{f}}^{++}}{{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit p}_{{s}}}$
$1317$ $\pm1$ $\pm2$
 1997
MPS 18 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit p}}$
$1315$ $\pm5$ $\pm2$ 1
 1994 D
CBAR $0.0$ ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}^{0}}{{\mathit \pi}^{0}}{{\mathit \eta}}$
$1325.1$ $\pm5.1$
 1993
BKEI ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit p}}$
$1317.7$ $\pm1.4$ $\pm2.0$
 1993
VES 37 ${{\mathit \pi}^{-}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit N}}$
$1323$ $\pm8$ 1000 2
 1973
OSPK - 6 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{-}}{{\mathit \eta}}$
• • We do not use the following data for averages, fits, limits, etc. • •
$1312.5$ $\pm0.7$ $\pm2.6$ 3
 2020
RVUE 0.9 ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}^{0}}{{\mathit \pi}^{0}}{{\mathit \eta}}$ , ${{\mathit \pi}^{0}}{{\mathit \eta}}{{\mathit \eta}}$ , ${{\mathit \pi}^{0}}{{\mathit K}^{+}}{{\mathit K}^{-}}$
$1306.0$ $\pm0.8$ $\pm1.3$ 4
 2019
JPAC 191 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}^{(')}}{{\mathit \pi}^{-}}{{\mathit p}}$
$1307$ $\pm1$ $\pm6$ 5
 2018
JPAC ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit p}}$
$1315$ $\pm12$ 6
 2015
COMP 191 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}^{(')}}{{\mathit \pi}^{-}}{{\mathit p}}$
$1309$ $\pm4$
 2009
RVUE ${{\overline{\mathit p}}}{{\mathit p}}$ , ${{\mathit \pi}}{{\mathit N}}$
$1324$ $\pm5$
 1993 C
E760 0 ${{\overline{\mathit p}}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}^{0}}{{\mathit \eta}}{{\mathit \eta}}$ $\rightarrow$ 6 ${{\mathit \gamma}}$
$1336.2$ $\pm1.7$ 2561
 1981
SPEC + ${{\mathit \pi}^{\pm}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{\pm}}{{\mathit \eta}}$
$1330.7$ $\pm2.4$ 1653
 1981
SPEC - ${{\mathit \pi}^{\pm}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \pi}^{\pm}}{{\mathit \eta}}$
$1324$ $\pm8$ 6200 2, 7
 1973
OSPK - 6 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}}$ MM${}^{-}$
 1 The systematic error of 2 MeV corresponds to the spread of solutions.
 2 Error includes 5 MeV systematic mass-scale error.
 3 T-matrix pole with 2 poles, 2 channels ( ${{\mathit \pi}^{0}}{{\mathit \eta}}$ and ${{\mathit K}}{{\overline{\mathit K}}}$ ).
 4 The coupled-channel analysis of both the ${{\mathit \eta}}{{\mathit \pi}}$ and ${{\mathit \eta}^{\,'}}{{\mathit \pi}}$ systems using ADOLPH 2015 data. The mass is extracted from the T-matrix pole.
 5 Superseded by RODAS 2019 .
 6 ADOLPH 2015 value is derived from a Breit-Wigner fit with mass-dependent width taking the ${{\mathit \eta}}{{\mathit \pi}}$ and ${{\mathit \rho}}{{\mathit \pi}}$ channels into account.
 7 Missing mass with enriched MMS = ${{\mathit \eta}}{{\mathit \pi}^{-}}$ , ${{\mathit \eta}}$ = 2${{\mathit \gamma}}$.
References:
 ALBRECHT 2020
EPJ C80 453 Coupled channel analysis of ${\bar{p}p}\,\rightarrow \,\pi ^0\pi ^0\eta$, ${\pi ^0\eta \eta }$ and ${K^+K^-\pi ^0}$ at 900 MeV/c and of ${\pi \pi }$-scattering data
 RODAS 2019
PRL 122 042002 Determination of the pole position of the lightest hybrid meson candidate
 JACKURA 2018
PL B779 464 New analysis of $\eta\pi$ tensor resonances measured at the COMPASS experiment
PL B740 303 Odd and Even Partial Waves of ${{\mathit \eta}}{{\mathit \pi}^{-}}$ and ${{\mathit \eta}^{\,'}}{{\mathit \pi}^{-}}$ in ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}^{{(')}}}{{\mathit \pi}^{-}}{{\mathit p}}$ at 191 GeV/$\mathit c$
 ANISOVICH 2009
IJMP A24 2481 The Combined Analysis of ${{\mathit \pi}}$ ${{\mathit N}}$ $\rightarrow$ two mesons ${+}$ ${{\mathit N}}$ Reactions within Reggeon Exchanges and Data for ${{\mathit p}}$ ${{\overline{\mathit p}}}$ (at rest) $\rightarrow$ three mesons
 BARBERIS 2000H
PL B488 225 A Study of the Centrally Produced ${{\mathit \eta}}{{\mathit \pi}^{0}}$ and ${{\mathit \eta}}{{\mathit \pi}^{-}}$ Systems in ${{\mathit p}}{{\mathit p}}$ Interactions at 450 ${\mathrm {GeV/}}\mathit c$
 THOMPSON 1997
PRL 79 1630 Evidence for Exotic Meson Production in the Reaction ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit p}}$ at 18 ${\mathrm {GeV/}}\mathit c$
 AMSLER 1994D
PL B333 277 Observation of a New $\mathit I\mathit G(\mathit J{}^{PC}) = 1{}^{-}(0{}^{++})$ Resonance at 1450 MeV
 AOYAGI 1993
PL B314 246 Study of the ${{\mathit \eta}}{{\mathit \pi}^{-}}$ System in the ${{\mathit \pi}^{-}}{{\mathit p}}$ Reaction at 6.3 ${\mathrm {GeV/}}\mathit c$
 ARMSTRONG 1993C
PL B307 394 Evidence for ${{\mathit \eta}}{{\mathit \eta}}$ Resonances in Antiproton Proton Annihilations at 2950 $<$ $\sqrt {s }$ $<$ 3620 MeV
PL B313 276 Study of ${{\mathit \pi}^{-}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit N}}$ and ${{\mathit \pi}^{-}}$ ${{\mathit N}}$ $\rightarrow$ ${{\mathit \eta}^{\,'}}{{\mathit \pi}^{-}}{{\mathit N}}$ Reactions at 37 ${\mathrm {GeV/}}\mathit c$
NP B183 349 Production of ${{\mathit \rho}^{\pm}}$, ${{\mathit g}{(1700)}^{\pm}}$, ${{\mathit A}_{{2}}^{\pm}}$, ${{\mathit K}^{*}{(890)}^{\pm}}$ and ${{\mathit K}^{*}{(1420)}^{\pm}}$ at 50 ${\mathrm {GeV/}}\mathit c$
PL 45B 154 Missing Mass Analysis of the ${{\mathit A}_{{2}}^{-}}$ at 6.0 ${\mathrm {GeV/}}\mathit c$
PRL 30 503 Study of the Decay ${{\mathit A}_{{2}}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}}$ via the Reaction ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{-}}{{\mathit p}}$ at 6.0 ${\mathrm {GeV/}}\mathit c$