28 research outputs found
Status of KLOE-2
In a few months the KLOE-2 detector is expected to start data taking at the
upgraded DANE -factory of INFN Laboratori Nazionali di
Frascati. It aims to collect 25 fb at the peak, and about 5
fb in the energy region between 1 and 2.5 GeV. We review the status and
physics program of the projectComment: 6 pages, 5 figures, to appear in the Proceedings of the PHIPSI09
Workshop, Oct 13-16, 2009, Beijing, Chin
Near threshold radiative 3 production in annihilation
We consider the final state in electron-positron
annihilation at cms energies not far from the threshold. Both initial and final
state radiations of the hard photon is considered but without interference
between them. The amplitude for the final state radiation is obtained by using
the effective Wess-Zumino-Witten Lagrangian for pion-photon interactions valid
for low energies. In real experiments energies are never such small that
and mesons would have negligible effect. So a phenomenological
Breit-Wigner factor is introduced in the final state radiation amplitude to
account for the vector mesons influence. Using radiative 3 production
amplitudes, a Monte Carlo event generator was developed which could be useful
in experimental studies.Comment: 15 pages, Latex, 6 figures. Misprints corrected. Version to be
published in JHE
Update of g-2 of the muon and Delta alpha
We update our Standard Model predictions for g-2 of the muon and for the
hadronic contributions to the running of the QED coupling, Delta
alpha^5_had(M_Z^2). Particular emphasis is put on recent changes in the
hadronic contributions from new data in the 2pi channel and from the energy
region just below 2 GeV.Comment: 6 pages, 10 figures, proceedings of the PhiPsi09 conference, 13-16
Oct. 2009, Beijing, Chin
Order p^6 chiral couplings from the scalar K Pi form factor
Employing results from a recent determination of the scalar KPi form factor
F_0^KPi within a coupled channel dispersion relation analysis \cite{JOP01}, in
this work we calculate the slope and curvature of F_0^KPi(t) at zero momentum
transfer. Knowledge of the slope and curvature of the scalar KPi form factor,
together with a recently calculated expression for F_0^KPi(t) in chiral
perturbation theory at order p^6, enable to estimate the O(p^6) chiral
constants C_12^r=(0.3 +- 5.4)10^-7 and (C_12^r+C_34^r)=(3.2 +- 1.5)10^-6. Our
findings also allow to estimate the contribution coming from the C_i to the
vector form factor F_+^KPi(0) which is crucial for a precise determination of
|V_us| from K_l3 decays. Our result F_+^KPi(0)|_C_i^r=-0.018 +- 0.009, though
inflicted with large uncertainties, is in perfect agreement with a previous
estimate by Leutwyler and Roos already made twenty years ago.Comment: 19 pages, discussion of scale dependence of the chiral couplings
added; version to appear in JHE
Limit on the production of a new vector boson in , U with the KLOE experiment
The recent interest in a light gauge boson in the framework of an extra U(1)
symmetry motivates searches in the mass range below 1 GeV.
We present a search for such a particle, the dark photon, in , U based on 28 million
events collected at DANE
by the KLOE experiment. The production by initial-state radiation
compensates for a loss of sensitivity of previous KLOE , searches due to the small branching ratios in
the resonance region. We found no evidence for a signal and set a
limit at 90\% CL on the mixing strength between the photon and the dark photon,
, in the U mass range between and ~MeV. Above 700 MeV
this new limit is more stringent than previous ones.Comment: 6 pages, 9 figures, 1 table, submitted to Phys. Lett.
Measurement of the transition form factor with the KLOE detector
A measurement of the vector to pseudoscalar conversion decay with the KLOE experiment is presented. A sample of signal
events was selected from a data set of 1.7 fb of collisions at
collected at the DANE collider. These
events were used to obtain the first measurement of the transition form factor
and a new measurement of the branching ratio of the
decay: . The result improves
significantly on previous measurements and is in agreement with theoretical
predictions.Comment: 13 pages, 4 figures; matches published versio
Measurement of {\eta} meson production in {\gamma}{\gamma} interactions and {\Gamma}({\eta}-->{\gamma}{\gamma}) with the KLOE detector
We present a measurement of {\eta} meson production in photon-photon
interactions produced by electron-positron beams colliding with \sqrt{s}=1 GeV.
The measurement is done with the KLOE detector at the \phi-factory DA{\Phi}NE
with an integrated luminosity of 0.24 fb^{-1}. The e^+e^- --> e^+e^-{\eta}
cross section is measured without detecting the outgoing electron and positron,
selecting the decays {\eta}-->{\pi}^+{\pi}^-{\pi}^0 and
{\eta}-->{\pi}^0{\pi}^0{\pi}^0. The most relevant background is due to e^+e^-
--> {\eta}{\gamma} when the monochromatic photon escapes detection. The cross
section for this process is measured as {\sigma}(e^+e^- -->{\eta}{\gamma}) =
(856 \pm 8_{stat} \pm 16_{syst}) pb. The combined result for the e^+e^-
-->e^+e^-{\eta} cross section is {\sigma}(e^+e^- -->e^+e^-{\eta}) = (32.72 \pm
1.27_{stat} \pm 0.70_{syst}) pb. From this we derive the partial width
{\Gamma}({\eta}-->{\gamma}{\gamma}) = (520 \pm 20_{stat} \pm 13_{syst}) eV.
This is in agreement with the world average and is the most precise measurement
to date.Comment: Version accepted by JHE
Measurement of with KLOE experiment
We report the measurement of the ratio analyzing a large sample of
decays recorded with the KLOE experiment at the
DANE collider, corresponding to an integrated luminosity of 558
pb. The process is supposed to proceed both
via a resonant contribution, mediated by the meson, and a non resonant
direct term, connected to the box anomaly. The presence of the direct term
affects the partial width value. Our result is in agreement with a recent CLEO measurement, which differs by
more 3 from the average of previous results