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${{\mathit \eta}^{\,'}{(958)}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}}{{\mathit \pi}}$ DECAY PARAMETERS
$\vert $MATRIX ELEMENT$\vert ^2$ ${}\propto$ 1 + $\mathit a~Y$ + $\mathit b~Y{}^{2}$ + $\mathit c~X$ + $\mathit d~X{}^{2}$

$\mathit X$ and $\mathit Y$ are Dalitz variables and $\mathit a,~b,~c$, and $\mathit d$ are real-valued parameters. May be different for ${{\mathit \eta}^{\,'}{(958)}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ and ${{\mathit \eta}^{\,'}{(958)}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ decays. We do not average measurements in the section below because parameter values from each experiment are strongly correlated.

$\mathit b$ decay parameter

INSPIRE   PDGID:

M002DPB

VALUE EVTS DOCUMENT ID TECN  COMMENT • • We do not use the following data for averages, fits, limits, etc. • • $-0.049$ $\pm0.006$ $\pm0.006$ 351k ABLIKIM 2018 BES3 ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ $-0.073$ $\pm0.014$ $\pm0.005$ 56k ABLIKIM 2018 BES3 ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ $-0.063$ $\pm0.014$ $\pm0.005$ 124k ADLARSON 2018 A A2MM ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ $-0.052$ $\pm0.001$ $\pm0.002$ 1 GONZALEZ-SOLI.. 2018 A RVUE ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ $-0.069$ $\pm0.019$ $\pm0.009$ 44k 2 ABLIKIM 2011 BES3 ${{\mathit J / \psi}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ $-0.063$ $\pm0.028$ $\pm0.004$ 15k 3 BLIK 2009 GAM4 32.5 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}^{\,'}}{{\mathit n}}$ $-0.106$ $\pm0.028$ $\pm0.014$ 20k 4 DOROFEEV 2007 VES 27 ${{\mathit \pi}^{-}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \eta}^{\,'}}{{\mathit n}}$ , ${{\mathit \pi}^{-}}$ ${{\mathit A}}$ $\rightarrow$ ${{\mathit \eta}^{\,'}}{{\mathit \pi}^{-}}{{\mathit A}^{*}}$ 1  Theoretical analysis of ADLARSON 2018A using resonance chiral perturbation theory to one loop. 2  See ABLIKIM 2011 for the full correlation matrix. 3  From ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ decay. 4  From ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ decay.

References:

ABLIKIM 2018 PR D97 012003 Measurement of the Matrix Elements for the Decays ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ and ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ ADLARSON 2018A PR D98 012001 Measurement of the decay $\eta^{\prime}\to\pi^{0}\pi^{0}\eta$ at MAMI GONZALEZ-SOLIS 2018A EPJ C78 758 $\eta ^{\prime }\rightarrow \eta \pi \pi $ decays in unitarized resonance chiral theory ABLIKIM 2011 PR D83 012003 Measurement of the Matrix Element for the Decay ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ BLIK 2009 PAN 72 231 Measurement of the Matrix Element for the Decay ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{0}}{{\mathit \pi}^{0}}$ with the GAMS-4$\pi $ Spectrometer DOROFEEV 2007 PL B651 22 Study of ${{\mathit \eta}^{\,'}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ Dalitz Plot

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