pdgLive

$K_{S}^{0}$ 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 “

C P

violation in

K_{L}

decays” in the

K_{L}^{0}

Particle Listings. The result labeled “OUR FIT Assuming

C P T

” [``OUR FIT Not assuming

C P T

''] includes all measurements except those with the comment “Not assuming

C P T

” [``Assuming

C P T

'']. Measurements with neither comment do not assume

C P T

and enter both fits.

VALUE (

10^{- 10}

s)

EVTS

DOCUMENT ID

TECN

COMMENT

0.89564 \pm 0.00033

OUR FIT Not assuming

C P T

0.8954 \pm 0.0004

OUR FIT Error includes scale factor of 1.1. Assuming

C P T

0.89589

\pm 0.00070

KTEV

Not assuming

C P T

0.89623

\pm 0.00047

KTEV

Assuming

C P T

0.89562

\pm 0.00029

\pm 0.00043

20M

KLOE

Not assuming

C P T

0.89598

\pm 0.00048

\pm 0.00051

16M

NA48

0.8971

\pm 0.0021

NA31

0.8941

\pm 0.0014

\pm 0.0009

SCHWINGENHEUE..

E773

Assuming

C P T

0.8929

\pm 0.0016

E731

Assuming

C P T

• • We do not use the following data for averages, fits, limits, etc. • •

0.8965

\pm 0.0007

KTEV

Assuming

C P T

0.8958

\pm 0.0013

KTEV

Not assuming

C P T

0.8920

\pm 0.0044

214k

SPEC

0.905

\pm 0.007

SPEC

0.881

\pm 0.009

26k

SPEC

892.6 \pm 3.2 \pm 0.2 \times 10^{- 3}

SPEC

0.8937

\pm 0.0048

6M

ASPK

0.8958

\pm 0.0045

50k

HBC

0.856

\pm 0.008

19994

HBC

0.872

\pm 0.009

20000

DBC

¹	The two ABOUZAID 2011 values use the same full KTeV dataset from 1996, 1997, and 1999. The first enters the ''assuming $C P T$ '' fit and the second enters the ''not assuming $C P T$ '' fit.

²	ABOUZAID 2011 fit has $Δ m$ , $τ_{s}$ , $ϕ_{ϵ}$ , Re( $ϵ^{^{'}} / ϵ$ ), and Im( $ϵ^{^{'}} / ϵ$ ) as free parameters. See Im( $ϵ^{^{'}} / ϵ$ ) in the '' $K_{L}^{0}$ $C P$ violation'' section for correlation information.

³

ABOUZAID 2011 fit has

Δ m

and

τ_{s}

free but constrains

ϕ_{ϵ}

to the Superweak value, i.e. assumes

C P T

. This

τ_{s}

value is correlated with their

Δ m

=

m_{K_{L}^{0}} - m_{K_{S}^{0}}

measurement in the

K_{L}^{0}

listings. The correlation coefficient

ρ (τ_{s}

,

Δ m

) =

- 0.670

.

⁴	Fit to the proper time distribution.

⁵

This ALAVI-HARATI 2003 fit has

Δ m

and

τ_{s}

free but constrains

ϕ_{+ -}

to the Superweak value, i.e. assumes

C P T

. This

τ_{s}

value is correlated with their

Δ m

=

m_{K_{L}^{0}} - m_{K_{S}^{0}}

measurement in the

K_{L}^{0}

listings. The correlation coefficient

ρ (τ_{s}, Δ m)

=

- 0.396

. Superseded by ABOUZAID 2011.

⁶	This ALAVI-HARATI 2003 fit has $Δ m$ , $ϕ_{+ -}$ , and $τ_{K_{S}}$ free. See $ϕ_{+ -}$ in the `` $K_{L}$ $C P$ violation'' section for correlation information. Superseded by ABOUZAID 2011.

⁷	ARONSON 1982 find that $K_{S}^{0}$ mean life may depend on the kaon energy.

⁸

CARITHERS 1975 measures the

Δ m

dependence of the total decay rate (inverse mean life) to be

Γ (K_{S}^{0})

=

[(1.122

\pm 0.004) + 0.16 (Δ m - 0.5348) / Δ m] 10^{10}

/s, or, in terms of mean life, CARITHERS 1975 measures

τ_{s}

= (

0.8913

\pm 0.0032

)

-

0.238

[

Δ m

-

0.5348

] . We have adjusted the measurement to use our best values of (

Δ m

=

0.5293

\pm 0.0009

) . 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 ( $0.865$ $\pm 0.009$ ) because of a correction in the shift due to $η_{+ -}$ . 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.

PR D83 092001

Precise Measurements of Direct

C P

Violation,

C P T

Symmetry, and other Parameters in the Neutral Kaon System

EPJ C71 1604

Precision Measurement of

K_{S}^{0}

Meson Lifetime with the KLOE Detector

PR D67 012005

Measurements of Direct

C P

Violation,

C P T

Symmetry, and other Parameters in the Neutral Kaon System

PR D70 079904 (errat.)

Erratum to ALAVI-HARATI 2003: “Measurements of Direct

C P

-Violation,

C P T

Symmetry, and other Parameters in the Neutral Kaon System''

PL B537 28

A Measurement of the

K_{S}^{0}

Lifetime

ZPHY C73 629

Measurement of the

K_{S}^{0}

Mean Lifetime from

π^{+} π^{-}

and

π^{0} π^{0}

Decays using

K_{L}^{0}

Decays to Determine the Acceptance

PRL 74 4376

C P T

Tests in the Neutral Kaon System

PRL 70 1199

New Measurements of the Neutral Kaon Parameters

Δ_{m}

,

τ_{S}

,

Φ_{00}

-

Φ_{+ -}

, and

Φ_{+ -}

PR D55 6625

C P

and

C P T

Symmetry Test from the Two Pion Decays of the Neutral Kaon with the FNAL E731 Detector

PRL 59 18

Measurement of the Lifetime of

K_{S}^{0}

Mesons in the Momentum Range 100 to 350

GeV / c

PRL 48 1306

Determination of the Fundamental Parameters of the

K^{0} {\overset{―}{K}}^{0}

System in the Energy Range 30-110 GeV

PL 116B 73

Interaction of the

K^{0} {\overset{―}{K}}^{0}

System with External Fields

PR D28 476

Energy Dependence of the Fundamental Parameters of the

K^{0} {\overset{―}{K}}^{0}

System. 1. Experimental Analysis

PR D28 495

Energy Dependence of the Fundamental Parameters of the

K^{0} {\overset{―}{K}}^{0}

System. 2. Theoretical Formalism

NC 32A 236

New Measurement of the

K_{S}^{0}

Lifetime

PRL 34 1244

Measurement of the Phase of the

C P

Nonconservation Parameter

η_{+ -}

and

K_{S}^{0}

Total Decay Rate

PL 48B 487

A New Determination of the

K^{0}

\to

π^{+} π^{-}

Decay Parameters

PL 52B 119

The Phase

ϕ_{+ -}

of

C P

Violation in the

K^{0}

\to

π^{+} π^{-}

Decay

NP B48 343

Measurement of the

K_{S}^{0}

Mean Life

PL 27B 58

The Decay Rate of the Short Lived Neutral Kaon

PR 171 1418

Measurement of the Lifetime of the Short-Lived Neutral

K

Meson

Except where otherwise noted, content of the 2024 Review of Particle Physics is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license. The publication of the Review of Particle Physics is supported by US DOE, MEXT (Japan), INFN (Italy) and CERN. Individual collaborators receive support for their PDG activities from their respective institutes or funding agencies. © 2024. See LBNL disclaimers.