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${{\mathit n}}$ $\rightarrow$ ${{\mathit p}}{{\mathit e}^{-}}{{\overline{\mathit \nu}}_{{e}}}$ DECAY PARAMETERS

See the above “Note on Baryon Decay Parameters.” For discussions of recent results, see the references cited at the beginning of the section on the neutron mean life. For discussions of the values of the weak coupling constants ${\mathit g}_{{{\mathit A}}}$ and ${\mathit g}_{{{\mathit V}}}$ obtained using the neutron lifetime and asymmetry parameter$~\mathit A$, comparisons with other methods of obtaining these constants, and implications for particle physics and for astrophysics, see DUBBERS 1991 and WOOLCOCK 1991 . For tests of the $\mathit V−\mathit A$ theory of neutron decay, see EROZOLIMSKII 1991B, MOSTOVOI 1996 , NICO 2005 , SEVERIJNS 2006 , and ABELE 2008 .

${{\overline{\mathit \nu}}_{{e}}}$ ASYMMETRY PARAMETER $\mathit B$

This is the neutron-spin antineutrino-momentum correlation coefficient. In the Standard Model, $\mathit B$ is related to $\lambda {}\equiv\mathit g_{A}/\mathit g_{V}$ by $\mathit B$ = 2$\lambda (\lambda $ $−$ 1) $/$ (1 + 3$\lambda {}^{2}$); this assumes that $\mathit g_{A}$ and $\mathit g_{V}$ are real.

VALUE

DOCUMENT ID

TECN

COMMENT

$\bf{ 0.9807 \pm0.0030}$

OUR AVERAGE

$0.9802$ $\pm0.0034$ $\pm0.0036$

CNTR

Cold ${{\mathit n}}$, polarized

$0.967$ $\pm0.006$ $\pm0.010$

CNTR

Cold ${{\mathit n}}$, polarized

$0.9801$ $\pm0.0046$

CNTR

Cold ${{\mathit n}}$, polarized

$0.9894$ $\pm0.0083$

CNTR

Cold ${{\mathit n}}$, polarized

$1.00$ $\pm0.05$

CNTR

Cold ${{\mathit n}}$, polarized

$0.995$ $\pm0.034$

CNTR

Cold ${{\mathit n}}$, polarized

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

$0.9876$ $\pm0.0004$

CNTR

Inferred

¹	MOSTOVOI 2001 calculates this from its measurement of $\lambda =\mathit g_{\mathit A}/\mathit g_{\mathit V}$ above.

References:

PRL 99 191803

Measurement of the Neutrino Asymmetry Parameter $\mathit B$ in Neutron Decay

PL B619 263

A Measurement of the Antineutrino Asymmetry $\mathit B$ in Free Neutron Decay

PAN 64 1955

Experimental Value of $\mathit G_{a}/G_{v}$ from a Measurement of Both $\mathit P$-odd Correlations in Free-neutron Decay

JETP 86 1074

Measurement of the Antineutrino Escape Asymmetry with Respect to the Spin of the Decaying Neutron

PRL 75 794

Measurements of the Antineutrino Spin Asymmetry in $\beta $ Decay of the Neutron and Restrictions on the Mass of a Right Handed Gauge Boson

PR C1 1693

Measurement of Angular Correlations in the Decay of Polarized Neutrons

PL 33B 351

Angular Correlation between the Neutron Spin and the Antineutrino Momentum in the Neutron Decay

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