Speaker
Description
KLOE and KLOE-2 experiment, operated at the DA$\Phi$NE facility of Frascati, acquired almost 8 fb$^{-1}$ of data at the $\phi$ peak resonance.
The two samples together represent the largest statistics ever collected at an $e^+ e^-$ collider at 1.02 GeV center-of-mass energy.
With about 2.4 $\times 10^{10} \,\phi$ and $3.1 \times 10^8 \,\eta$ meson events available for data analysis, KLOE-2 can give an important contribution to hadron spectroscopy and Dark Force research fields. Moreover, thanks to the installation in both DA$\Phi$NE arms of two tagger station, KLOE-2 can also investigate the $\gamma\gamma$ fusion.
The $\eta \to \pi^0 \gamma \gamma$ decay is considered a ChPT golden mode because of its sensitivity to the $p^6$ term on both the branching ratio (BR) and the M($\gamma\gamma$) spectrum. There is a 4.5 $\sigma$ discrepancy between the KLOE preliminary BR measurement, obtained with 450 pb$^{-1}$, and the most accurate one from Crystal Ball.
By increasing sample statistics KLOE-2 can confirm or solve this discrepancy.
We are also active in the dark force field by testing an alternative model where the Dark Force mediator is an hypothetical leptophobic B boson that can couple only to barions with same quantum numbers of the $\omega$ meson. For masses less than 600 MeV the expected dominant decay channel is into $\pi^0\gamma$, thus we are investigated this possibility in the $\phi \to \eta B\to \eta \pi^0\gamma$ channel with $\eta \to \gamma \gamma$.
KLOE-2 aims to precisely measure the $\pi^0$ decay width into $\gamma \gamma$ by profiting of the $\pi^0$ production through $\gamma\gamma$ fusion. The status of the $\gamma^{\ast}\gamma^{\ast}\to \pi^0$ analysis will be reported.
We want also to precisely measure the $\omega$ cross section in the $e^+ e^- \to \pi^+ \pi^- \pi^0 \gamma_{\rm ISR}$ channel using the Initial State Radiation (ISR) method. Promising results on this item will be also presented.
KLOE-2 searched for the P and CP violating decay $\eta\rightarrow\pi^+\pi^-$ by exploiting the radiative $\phi\rightarrow\eta\gamma$ process with 1.6~fb$^{-1}$ of KLOE data.
No signal is observed in the $\pi^+\pi^-$ invariant mass spectrum and a limit on the branching ratio at 90\% CL has been extracted.
The limit results to be B($\eta\rightarrow\pi^+\pi^-$)$< 4.9 \times 10^{−6}$, three times lower than previous KLOE one,
the combination of the two KLOE limits gives a B($\eta\rightarrow\pi^+\pi^-$)$< 4.4 \times 10^{−6}$.
Moreover, KLOE-2 perform the search for the double suppressed $\phi\rightarrow \eta\, \pi^+ \pi^- $ and the conversion
$\phi\rightarrow \eta\, \mu^+ \mu^- $ decays with both $\eta \to \gamma \gamma$ and $\eta \to 3\pi^0$. Clear signal are observed for the first time.
