pdgLive

${{\mathit \eta}^{\,'}{(958)}}$ MASS

INSPIRE JSON (beta) PDGID:

VALUE (MeV)

EVTS

DOCUMENT ID

TECN

COMMENT

$\bf{ 957.78 \pm0.06}$

OUR AVERAGE

$957.793$ $\pm0.054$ $\pm0.036$

3.9k

CLEO

${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \eta}^{\,'}}$

$957.9$ $\pm0.2$ $\pm0.6$

4800

SPEC

1.68 ${{\mathit p}}$ ${{\mathit d}}$ $\rightarrow$ ${}^{3}\mathrm {He}$ ${{\mathit \eta}^{\,'}}$

$957.46$ $\pm0.33$

MMS

${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit n}}$ MM

$958.2$ $\pm0.5$

1414

HBC

2.2 ${{\mathit K}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \eta}^{\,'}}$

$958$ $\pm1$

400

HBC

2.9 ${{\mathit K}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \Lambda}}{{\mathit \eta}^{\,'}}$

$956.1$ $\pm1.1$

3415

CNTR

1.6 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \eta}^{\,'}}$

• • We do not use the following data for averages, fits, limits, etc. • •

$957.5$ $\pm0.2$

BES2

${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$

$959$ $\pm1$

$630$

VES

36 ${{\mathit \pi}^{-}}$ ${}^{}\mathrm {Be}$ ${{\mathit \pi}^{-}}$ ${{\mathit \eta}^{\,'}}$ ${{\mathit \eta}}$ ${}^{}\mathrm {Be}$

$958$ $\pm1$

340

OMEG

300 ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit p}}{{\mathit p}}{{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$

$958.2$ $\pm0.4$

622

DM2

${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$

$957.8$ $\pm0.2$

2420

DM2

${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$

$956.3$ $\pm1.0$

$143$

MRK2

${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}{{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$

$957.4$ $\pm1.4$

535

CNTR

1.6 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit n}}{{\mathit \eta}^{\,'}}$

$957$ $\pm1$

HBC

1.7$-$2.7 ${{\mathit K}^{-}}{{\mathit p}}$

¹	Using all ${{\mathit \eta}^{\,'}}$ decays.

²	Systematic uncertainty not estimated.

³	Using ${{\mathit \eta}^{\,'}}$ decays into neutrals. Not independent of the other listed BASILE 1971 ${{\mathit \eta}^{\,'}}$ mass measurement.

Except where otherwise noted, content of the 2025 Review of Particle Physics is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license. The publication of the Review of Particle Physics is supported by US DOE, MEXT (Japan), INFN (Italy) and CERN. Individual collaborators receive support for their PDG activities from their respective institutes or funding agencies. © 2025. See LBNL disclaimers.