Speaker
Ms
Li Balkestahl
(Uppsala University)
Description
The KLOE experiment has collected 2.5 fb-1 at the peak of
the phi resonance at the e+e- collider DAPHNE in Frascati.
A new beam crossing scheme, allowing for a reduced beam
size and increased luminosity, is operating at DAPHNE. The
upgraded KLOE-2 detector is successfully rolled in inside
this new interaction region and is ready to acquire collision
data.
The V-->Pgamma Dalitz decays, associated to internal conversion
of the photon into a lepton pair, are not well described by
the Vector Meson Dominance (VMD) models, as in the case of the
process omega --> pi0 mu+ mu-, measured by the NA60 collaboration.
The only existing data on phi --> eta e+ e- come from the SND
experiment, which has measured the Mee invariant mass distribution
on the basis of 213 events. At KLOE, a detailed study of this
decay has been performed using both eta-->pipipi final states.
Simple analysis cuts provide clean signal events, with a residual
background contamination of 2-3%. With the fully neutral eta decay
channel, we obtain the measurement of the branching fraction for
the process phi --> eta e+ e-, with an accuracy improved by a
factor of five with respect to the previous most precise measurement,
and of the slope of the transition form factor, which is in agreement
with VMD expectations.
We have also studied the decay phi --> pi0 e+ e-, where no data
are available on transition form factor. Dedicated analysis cuts
strongly reduce the main background component of Bhabha events to
~20%, leading to ~4000 signal events in the whole KLOE data set.
We have also obtained a new, precise results on the isospin-violating
decay eta-->pi+pi-pi0, sensitive to the light-quark mass ratio. The
first study, overcoming in precision previous results published in
year 2008-2010, was suggested by the theoretical work: Leutwyler,
Mod.Phys.Lett. A28 (2013) 1360014, aiming to a better determination
of the light-quark mass ratio through the dispersive analysis of the
eta--> 3 pi decay.
Primary author
Ms
Li Balkestahl
(Uppsala University)
