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${{\mathit \Sigma}^{-}}$ DECAY PARAMETERS

See the ``Note on Baryon Decay Parameters'' in the neutron Listings. Older, outdated results have been omitted.

${\mathit g}_{{{\mathit A}}}/{\mathit g}_{{{\mathit V}}}$ FOR ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$

INSPIRE   PDGID:

S020AV2

Measurements with fewer than 500 events have been omitted. Where necessary, signs have been changed to agree with our conventions, which are given in the “Note on Baryon Decay Parameters” in the neutron Listings. What is actually listed is $\vert \mathit g_{1}/\mathit f_{1}-0.237\mathit g_{2}/\mathit f_{1}\vert $. This reduces to ${\mathit g}_{{{\mathit A}}}/{\mathit g}_{{{\mathit V}}}{}\equiv$ $\mathit g_{1}(0)/\mathit f_{1}$(0) on making the usual assumption that $\mathit g_{2}$ = 0. See also the note on HSUEH 1988 .

VALUE EVTS DOCUMENT ID TECN  COMMENT $\bf{ 0.340 \pm0.017}$ OUR AVERAGE $+0.327$ $\pm0.007$ $\pm0.019$ 50k 1 HSUEH 1988 SPEC ${{\mathit \Sigma}^{-}}$ 250 GeV $+0.34$ $\pm0.05$ 4456 2 BOURQUIN 1983 C SPEC SPS hyperon beam $0.385$ $\pm0.037$ 3507 3 TANENBAUM 1974 ASPK • • We do not use the following data for averages, fits, limits, etc. • • $0.29$ $\pm0.07$ 25k HSUEH 1985 SPEC See HSUEH 1988 $0.17$ ${}^{+0.07}_{-0.09}$ 519 DECAMP 1977 ELEC Hyperon beam 1  The sign is, $\mathit with~our~conventions$, unambiguously positive. The value assumes, as usual, that $\mathit g_{2}$ = 0. If $\mathit g_{2}$ is included in the fit, than (with our sign convention) $\mathit g_{2}$ = $-0.56$ $\pm0.37$, with a corresponding reduction of ${\mathit g}_{{{\mathit A}}}/{\mathit g}_{{{\mathit V}}}$ to $+0.20$ $\pm0.08$. 2  BOURQUIN 1983C favors the positive sign by at least 2.6 standard deviations. 3  TANENBAUM 1974 gives $0.435$ $\pm0.035$, assuming no $\mathit q{}^{2}$ dependence in $\mathit g_{\mathit A}$ and ${\mathit g}_{{{\mathit V}}}$. The listed result allows $\mathit q{}^{2}$ dependence, and is taken from HSUEH 1988 .

References:

HSUEH 1988 PR D38 2056 High Precision Measurement of Polarized ${{\mathit \Sigma}^{-}}$ $\beta $ Decay HSUEH 1985 PRL 54 2399 Measurement of the Electron Asymmetry in the $\beta $ Decay of Polarized ${{\mathit \Sigma}^{-}}$ Hyperons BOURQUIN 1983C ZPHY C21 17 Measurements of Hyperon Semileptonic Decays at the CERN Super Proton Synchrotron. 3. The ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$ Decay Mode DECAMP 1977 PL 66B 295 The Ratio $\mathit g_{a}$/g$_{v}$ in the Decay ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$ TANENBAUM 1974 PRL 33 175 |$\mathit g_{a}$/g$_{v}$| in the Decay ${{\mathit \Sigma}^{-}}$ $\rightarrow$ ${{\mathit n}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}}$

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