${{\mathit K}_S^0}$ MEAN LIFE

For earlier measurements, beginning with BOLDT 1958B, see our 1986 edition, Physics Letters 170B 130 (1986).
OUR FIT is described in the note on “$\mathit CP$ violation in ${{\mathit K}_{{{L}}}}$ decays” in the ${{\mathit K}_L^0}$ Particle Listings. The result labeled “OUR FIT Assuming $\mathit CPT$” [``OUR FIT Not assuming $\mathit CPT$''] includes all measurements except those with the comment “Not assuming $\mathit CPT$” [``Assuming $\mathit CPT$'']. Measurements with neither comment do not assume $\mathit CPT$ and enter both fits.

INSPIRE   JSON  (beta) PDGID:
S012T
VALUE ($ 10^{-10} $ s) EVTS DOCUMENT ID TECN  COMMENT
$\bf{ 0.89564 \pm0.00033}$ OUR FIT  Not assuming $\mathit CPT$
$\bf{ 0.8954 \pm0.0004}$ OUR FIT  Error includes scale factor of 1.1.  Assuming $\mathit CPT$
$0.89589$ $\pm0.00070$ 1, 2
ABOUZAID
2011
KTEV Not assuming $\mathit CPT$
$0.89623$ $\pm0.00047$ 1, 3
ABOUZAID
2011
KTEV Assuming $\mathit CPT$
$0.89562$ $\pm0.00029$ $\pm0.00043$ 20M 4
AMBROSINO
2011
KLOE Not assuming $\mathit CPT$
$0.89598$ $\pm0.00048$ $\pm0.00051$ 16M
LAI
2002C
 NA48
$0.8971$ $\pm0.0021$
BERTANZA
1997
NA31
$0.8941$ $\pm0.0014$ $\pm0.0009$
SCHWINGENHEUE..
1995
E773 Assuming $\mathit CPT$
$0.8929$ $\pm0.0016$
GIBBONS
1993
E731 Assuming $\mathit CPT$
• • We do not use the following data for averages, fits, limits, etc. • •
$0.8965$ $\pm0.0007$ 5
ALAVI-HARATI
2003
KTEV Assuming $\mathit CPT$
$0.8958$ $\pm0.0013$ 6
ALAVI-HARATI
2003
KTEV Not assuming $\mathit CPT$
$0.8920$ $\pm0.0044$ 214k
GROSSMAN
1987
SPEC
$0.905$ $\pm0.007$ 7
ARONSON
1982B
 SPEC
$0.881$ $\pm0.009$ 26k
ARONSON
1976
SPEC
$892.6 \pm3.2 \pm0.2 \times 10^{-3}$ 8
CARITHERS
1975
SPEC
$0.8937$ $\pm0.0048$ 6M
GEWENIGER
1974B
 ASPK
$0.8958$ $\pm0.0045$ 50k 9
SKJEGGESTAD
1972
HBC
$0.856$ $\pm0.008$ 19994 10
DONALD
1968B
 HBC
$0.872$ $\pm0.009$ 20000 9, 10
HILL
1968
DBC
1  The two ABOUZAID 2011 values use the same full KTeV dataset from 1996, 1997, and 1999. The first enters the ''assuming $\mathit CPT$'' fit and the second enters the ''not assuming $\mathit CPT$'' fit.
2  ABOUZAID 2011 fit has $\Delta \mathit m$, ${{\mathit \tau}_{{{s}}}}$, ${{\mathit \phi}_{{{\epsilon}}}}$, Re(${{\mathit \epsilon}^{\,'}}/{{\mathit \epsilon}}$), and Im(${{\mathit \epsilon}^{\,'}}/{{\mathit \epsilon}}$) as free parameters. See Im(${{\mathit \epsilon}^{\,'}}/{{\mathit \epsilon}}$) in the ''${{\mathit K}_L^0}$ $\mathit CP$ violation'' section for correlation information.
3  ABOUZAID 2011 fit has $\Delta \mathit m$ and ${{\mathit \tau}_{{{s}}}}$ free but constrains ${{\mathit \phi}_{{{\epsilon}}}}$ to the Superweak value, i.e. assumes $\mathit CPT$. This ${{\mathit \tau}_{{{s}}}}$ value is correlated with their $\Delta \mathit m$ = ${\mathit m}_{{{\mathit K}_L^0} }–{\mathit m}_{{{\mathit K}_S^0} }$ measurement in the ${{\mathit K}_L^0}$ listings. The correlation coefficient ${{\mathit \rho}}({{\mathit \tau}_{{{s}}}}$, $\Delta \mathit m$) = $-0.670$.
4  Fit to the proper time distribution.
5  This ALAVI-HARATI 2003 fit has $\Delta \mathit m$ and $\tau _{{{\mathit s}}}$ free but constrains $\phi _{+−}$ to the Superweak value, i.e. assumes $\mathit CPT$. This $\tau _{{{\mathit s}}}$ value is correlated with their $\Delta \mathit m$ = ${\mathit m}_{{{\mathit K}_L^0} }–{\mathit m}_{{{\mathit K}_S^0} }$ measurement in the ${{\mathit K}_L^0}$ listings. The correlation coefficient $\rho\mathrm {(\tau _{{{\mathit s}}},\Delta \mathit m)}$ = $-0.396$. Superseded by ABOUZAID 2011.
6  This ALAVI-HARATI 2003 fit has $\Delta \mathit m$, $\phi _{+−}$, and $\tau _{{{\mathit K}_{{{S}}}}}$ free. See $\phi _{+−}$ in the ``${{\mathit K}_{{{L}}}}$ $\mathit CP$ violation'' section for correlation information. Superseded by ABOUZAID 2011.
7  ARONSON 1982 find that ${{\mathit K}_S^0}$ mean life may depend on the kaon energy.
8  CARITHERS 1975 measures the $\Delta \mathit m$ dependence of the total decay rate (inverse mean life) to be $\Gamma\mathrm {({{\mathit K}_S^0} )}$ = $\lbrack{}(1.122$ $\pm0.004)+0.16{}(\Delta \mathit m-0.5348)/\Delta \mathit m\rbrack{}10^{10}$/s, or, in terms of mean life, CARITHERS 1975 measures ${{\mathit \tau}_{{{s}}}}$ = ( $0.8913$ $\pm0.0032$ ) $–$ $0.238$ [ $\Delta \mathit m$$–$ $0.5348$ ] . We have adjusted the measurement to use our best values of ( $\Delta \mathit m$ = $0.5293$ $\pm0.0009$ ) . Our first error is their experiment's error and our second error is the systematic error from using our best values.
9  HILL 1968 has been changed by the authors from the published value ($0.865$ $\pm0.009$) because of a correction in the shift due to $\eta _{+−}$. SKJEGGESTAD 1972 and HILL 1968 give detailed discussions of systematics encountered in this type of experiment.
10  Pre-1971 experiments are excluded from the average because of disagreement with later more precise experiments.
References