$({\mathit \tau}_{{{\mathit \tau}^{+}}}–{\mathit \tau}_{{{\mathit \tau}^{-}}})/{\mathit \tau}_{\mathrm {average}}$

INSPIRE  
Test of $\mathit CPT$ invariance.
VALUE CL% DOCUMENT ID TECN  COMMENT
$\bf{<7.0 \times 10^{-3}}$ 90 1
BELOUS
2014
BELL 711 fb${}^{-1}{\it{}E}^{\it{}ee}_{\rm{}cm}$ = 10.6 GeV
1  BELOUS 2014 quote limit on the absolute value of the relative lifetime difference.
References:
BELOUS 2014
PRL 112 031801 Measurement of the ${{\mathit \tau}}$ -lepton Lifetime at Belle