Speaker
Paolo Massarotti
(Naples University & INFN)
Description
The charged K lifetime, is an experimental input to the
determination of Vus. The present fractional uncertainty is about
0.2%,
however the available data show large discrepancies between the
measurements done using charged kaon decays in-flight and at-rest.
At KLOE two different methods have been developed: one based on
the measurement of the charged kaon decay length
and the other based on its decay time.
Both methods allow us to reach accuracies at the few per mil
level. These two independent methods allow us to assess part of the
systematic uncertainty.
Efficiency and resolution functions
are measured directly on data using an independent control sample.
The measurement of the charged kaon lifetime will be presented.
A new precise measurement of the absolute
BR(K+ -> pi pi0 (gamma)) has an important impact on the
world average of the charged kaon semileptonic BR's, because
of the NA48, ISTRA+ and E865 experiments that use the pi pi0 decay
in the normalization sample.
A pure K+ beam is tagged at KLOE by the recostruction of the
K- -> mu nu decays. The signal counting is given by a fit
to the distribution of the momentum of the charged decay particle
in the kaon rest frame assuming the pion mass.
The shapes of the signal and of the backgrond (mu nu and 3 bodies
decays)
are obtained from data control samples and MC.
Efficiency is
measured directly on data using an independent control sample.
The measurement of the BR(K+ -> pi pi0 (gamma)) will be presented.
Primary author
Collaboration KLOE
