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

PROTON ASYMMETRY PARAMETER $\mathit C$ INSPIRE search

Describes the correlation between the neutron spin and the proton momentum. In the Standard Model, $\mathit C$ is related to $\lambda {}\equiv\mathit g_{A}/\mathit g_{V}$ by $\mathit C$ = $−\mathit x_{c}$ ($\mathit A~+~B$) = $\mathit x_{c}$ 4$\lambda $/(1 + 3$\lambda {}^{2}$), where $\mathit x_{c}$ = 0.27484 is a kinematic factor; this assumes that $\mathit g_{A}$ and $\mathit g_{V}$ are real.
S017APC
VALUE DOCUMENT ID TECN  COMMENT
$-0.2377$ $\pm0.0010$ $\pm0.0024$
SCHUMANN
2008
CNTR Cold ${{\mathit n}}$, polarized
  References:
SCHUMANN 2008
PRL 100 151801 Measurement of the Proton Asymmetry Parameter in Neutron Beta Decay