Orateur
M.
Flavio Archilli
(University "Tor Vergata" (Rome))
Description
The KLOE detector is operated at DA$\Phi$NE, an $e^+ e^-$
collider running at a center of mass energy
$W = m_{\phi} \sim 1019.45$~MeV. $\phi$ mesons decay 34\%
of the time to a $K_S K_L$ pair. Detection
of a $K_L$ thus signals the presence of, ``tags'',
a $K_S$ and vice versa. With this technique, we
select a pure $K_S$ beam, which permits studies of
suppressed $K_S$ decays without
the overwhelming background from the $K_L$ component.
We present the result of a search for the $K_S \to e^+e^-$
decay obtained from the whole data set.
This is based on a sample of $\sim 650$ millions of $K_S$
decays tagged by the detection of a $K_L$ interaction
in the calorimeter.
$K_S \to e^+e^-$ decay is a $\Delta S = 1$ weak neutral
current process, suppressed by Standard Model
at the level of $\sim 2\times10^{-14}$.
These events are searched by selecting two charged
tracks from the interaction
region, and exploiting the high resolution of our drift chamber
in reconstructing the kaon invariant mass.
Further rejection comes from calorimeter particle
identification. No events survive our selection criteria,
resulting in un upper limit on the BR of $9.3 \times 10^{-9}$,~at~90\%~CL.
Auteur principal
M.
Flavio Archilli
(University "Tor Vergata" (Rome))
