# ${{\boldsymbol \eta}}$ MASS INSPIRE search

Recent measurements resolve the obvious inconsistency in previous ${{\mathit \eta}}$ mass measurements in favor of the higher value first reported by NA48 (LAI 2002 ). We use only precise measurements consistent with this higher mass value for our ${{\mathit \eta}}$ mass average.
VALUE (MeV) EVTS DOCUMENT ID TECN  COMMENT
$\bf{ 547.862 \pm0.017}$ OUR AVERAGE
$547.865$ $\pm0.031$ $\pm0.062$
 2014
CRYB ${{\mathit \gamma}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}}{{\mathit \eta}}$
$547.873$ $\pm0.005$ $\pm0.027$ 1M
 2012
SPEC ${{\mathit d}}$ ${{\mathit p}}$ $\rightarrow$ ${}^{3}\mathrm {He}{{\mathit \eta}}$
$547.874$ $\pm0.007$ $\pm0.029$
 2007 B
KLOE ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \phi}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \gamma}}$
$547.785$ $\pm0.017$ $\pm0.057$ 16k
 2007
CLEO ${{\mathit \psi}{(2S)}}$ $\rightarrow$ ${{\mathit J / \psi}}{{\mathit \eta}}$
$547.843$ $\pm0.030$ $\pm0.041$ 1134
 2002
NA48 ${{\mathit \eta}}$ $\rightarrow$ 3 ${{\mathit \pi}^{0}}$
• • • We do not use the following data for averages, fits, limits, etc. • • •
$547.311$ $\pm0.028$ $\pm0.032$ 1
 2005
SPEC ${{\mathit d}}$ ${{\mathit p}}$ $\rightarrow$ ${}^{3}\mathrm {He}{{\mathit \eta}}$
$547.12$ $\pm0.06$ $\pm0.25$
 1995 D
SPEC ${{\mathit \gamma}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit p}}$ , threshold
$547.30$ $\pm0.15$
 1992
SPEC ${{\mathit d}}$ ${{\mathit p}}$ $\rightarrow$ ${}^{3}\mathrm {He}{{\mathit \eta}}$
$547.45$ $\pm0.25$
 1974
SPEC ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit n}}$ neutrals
$548.2$ $\pm0.65$
 1965 C
HBC
$549.0$ $\pm0.7$ 148
 1964
HBC
$548.0$ $\pm1.0$ 91
 1962
HBC
$549.0$ $\pm1.2$ 53
 1962
HBC
1  ABDEL-BARY 2005 disagrees significantly with recent measurements of similar or better precision. See comment in the header.
References:
 NIKOLAEV 2014
EPJ A50 58 Determination of the ${{\mathit \eta}}$ Mass with the Crystal Ball at MAMI-B
 GOSLAWSKI 2012
PR D85 112011 New Determination of the Mass of the ${{\mathit \eta}}$ Meson at COSY-ANKE
 AMBROSINO 2007B
JHEP 0712 073 Precise Measurements of the ${{\mathit \eta}}$ Meson and the Neutral Kaon Masses with the KLOE Detector
 MILLER 2007
PRL 99 122002 Measurement of the ${{\mathit \eta}}$-Meson Mass using ${{\mathit \psi}{(2S)}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit J / \psi}}$
 ABDEL-BARY 2005
PL B619 281 A Precision Determination of the Mass of the ${{\mathit \eta}}$ Meson
 LAI 2002
PL B533 196 New Measurements of the ${{\mathit \eta}}$ and ${{\mathit K}^{0}}$ Masses
 KRUSCHE 1995D
ZPHY A351 237 Mass and $\Gamma (3{{\mathit \pi}^{0}})/\Gamma ({{\mathit \gamma}}{{\mathit \gamma}}$) Decay Branching Ratio of the ${{\mathit \eta}}$ Meson from the ${{\mathit p}}$ (${{\mathit \gamma}}$, ${{\mathit \eta}}$) ${{\mathit p}}$ Reaction
 PLOUIN 1992
PL B276 526 The ${{\mathit \eta}}$-Meson Mass
 DUANE 1974
PRL 32 425 New Upper Limit on the Width of the ${{\mathit X}{(958)}^{0}}$
 FOSTER 1965C
Thesis Study of ${{\mathit \eta}}$ Production and its Charged Decay Modes
 FOELSCHE 1964
PR 134 B1138 Multiple Pion Production in Interactions of Positive Pions with Protons near 1 BeV
 ALFF-STEINBERGER 1962
PRL 9 322 Production of Pion Resonances in ${{\mathit \pi}^{+}}{{\mathit p}}$ Interactions.
 BASTIEN 1962
PRL 8 114 Decay Modes and Width of the ${{\mathit \eta}}$ Meson