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

#### $\phi _{\mathit AV}$, PHASE OF ${\mathit g}_{{{\mathit A}}}$ RELATIVE TO ${\mathit g}_{{{\mathit V}}}$

Time reversal invariance requires this to be 0 or 180$^\circ{}$. This is related to $\mathit D$ given in the next data block and $\lambda$ ${}\equiv$ $\mathit g_{\mathit A}/\mathit g_{\mathit V}$ by sin$(\phi _{\mathit AV})$ ${}\equiv$ $\mathit D(1+3\lambda {}^{2})/2\vert \lambda \vert$; this assumes that $\mathit g_{A}$ and $\mathit g_{V}$ are real.
VALUE ($^\circ{}$) CL% DOCUMENT ID TECN  COMMENT
 $\bf{ 180.017 \pm0.026}$ OUR AVERAGE See the ideogram below.
$180.012$ $\pm0.028$ 68
 2012
CNTR Cold ${{\mathit n}}$ , polarized $>$ 91$\%$
$180.04$ $\pm0.09$
 2004
CNTR Cold ${{\mathit n}}$ , polarized
$180.08$ $\pm0.13$
 2000
CNTR Polarized $>$ 93$\%$
• • We do not use the following data for averages, fits, limits, etc. • •
$180.013$ $\pm0.028$
 2011
CNTR See CHUPP 2012
$179.71$ $\pm0.39$
 1978
CNTR Cold ${{\mathit n}}$ , polarized
$180.35$ $\pm0.43$
 1974
CNTR Cold ${{\mathit n}}$ , polarized
$181.1$ $\pm1.3$ 1
 1974
RVUE ${{\mathit n}}$ decay
$180.14$ $\pm0.22$
 1974
CNTR Cold ${{\mathit n}}$ , polarized
 1 KROPF 1974 reviews all data through 1972.

$\phi _{\mathit AV}$, PHASE OF ${\mathit g}_{{{\mathit A}}}$ RELATIVE TO ${\mathit g}_{{{\mathit V}}}$ ($^\circ{}$)
Conservation Laws:
TIME REVERSAL ($\mathit T$) INVARIANCE
References:
 CHUPP 2012
PR C86 035505 Search for a $\mathit T$-odd, $\mathit P$-even Triple Correlation in Neutron Decay
 MUMM 2011
PRL 107 102301 New Limit on Time-Reversal Violation in Beta Decay
 SOLDNER 2004
PL B581 49 New Limit on $\mathit T$ Violation in Neutron Decay
 LISING 2000
PR C62 055501 New Limit on the D Coefficient in Polarized Neutron Decay
 EROZOLIMSKII 1978
SJNP 28 48 False Effects in Investigation of Triple Correlation in Decay of Polarized Neutrons and New Results in Search for Time Parity Violation
 EROZOLIMSKII 1974
JETPL 20 345 Continuation of the Search for $\mathit T$ Invariance Violation in $\beta$ Decay of a Free Neutron
 KROPF 1974
ZPHY 267 129 Least Squares Adjustment of the Coupling Constants in Nuclear ${{\mathit \beta}}$ -Decay
 Also
NP A154 160 Least-Squares Adjustment of the Coupling Constants in ${{\mathit \beta}}$ -Decay
 STEINBERG 1974
PRL 33 41 New Experimental Limit on $\mathit T$ Invariance in Polarized Neutron $\beta$ Decay