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

#### TRIPLE CORRELATION COEFFICIENT $\mathit R$

Another test of time-reversal invariance. $\mathit R$ measures the polarization of the electron in the direction perpendicular to the plane defined by the neutron spin and the electron momentum. $\mathit R$ = 0 for T invariance.
VALUE DOCUMENT ID TECN  COMMENT
$+0.004$ $\pm0.012$ $\pm0.005$ 1
 2012
CNTR Mott polarimeter
• • We do not use the following data for averages, fits, limits, etc. • •
$+0.008$ $\pm0.015$ $\pm0.005$
 2009
CNTR See KOZELA 2012
 1 KOZELA 2012 also measures the polarization of the electron along the direction of the neutron spin. This is nonzero in the Standard Model; the correlation coefficient is $\mathit N$ = $+0.067$ $\pm0.011$ $\pm0.004$.
Conservation Laws:
TIME REVERSAL ($\mathit T$) INVARIANCE
References:
 KOZELA 2012
PR C85 045501 Measurement of the Transverse Polarization of Electrons Emitted in Free Neutron Decay
 KOZELA 2009
PRL 102 172301 Measurement of the Transverse Polarization of Electrons Emitted in Free-Neutron Decay