Relatore
Dr.
Barbara Sciascia
(LNF - INFN, Frascati)
Descrizione
The semileptonic BR's are relevant for the evaluation of the CKM
matrix element |Vus|. The measurement of the branching ratios for
the charged K semileptonic decays uses four independent samples
tagged by the following kaon decays: K+ -> mu2, K+ -> pi2, K- ->
mu2, and K- -> pi2. Using 410 pb-1 of total integrated luminosity
(2.5 fb-1), about 60 million tag decays have been identified and
divided into the four tag samples. This redundancy allows to keep
under control the systematic effects due to the tag selection.
The BR is evaluated separately for each tag sample, dividing by
the number of tag counts and correcting for acceptances. The
latter are obtained from MC simulations. Corrections are applied
to account for data-MC differences in tracking and clustering.
K+-e3 and K+-mu3 decays are selected, using kinematical cuts in
the kaon rest frame and time of flight particle identification.
The measurement of these BR's will be presented.
