26-30 July 2021
Europe/Berlin timezone

Hadron physics at KLOE/KLOE-2, results and perspectives (12'+3')

29 Jul 2021, 17:15


Parallel session talk QCD and Hadronic Physics T06: QCD and Hadronic Physics


Cao Bo (Uppsala University)


The KLOE-2 experiment, at the $e^+e^-$ DA$\Phi$NE collider in Frascati, acquired an integrated luminosity of about 5 fb$^{-1}$ with an upgraded KLOE apparatus. The whole KLOE/KLOE-2 data sample corresponds to 2.4 $\times 10^{10} \,\phi$ and $3.1 \times 10^8 \,\eta$ meson events allowing to develop a wide hadron physics program from rare meson decays to $\gamma\gamma$ fusion and dark forces.

KLOE-2 investigates the $\eta \to \pi^0 \gamma \gamma$ decay, an important test of ChPT because of its sensitivity to the $p^6$ term on both the branching ratio and the M($\gamma\gamma$) spectrum. A preliminary KLOE measurement, based on 450 pb$^{-1}$, provided a 4 sigma's lower value w.r.t. the most accurate determination of the BR from the Crystal Ball experiment. The new KLOE measurement performed with a larger data sample statistics will be presented.
By using the same five photon final state and
following the many KLOE-2 contributions to Dark Matter (DM) searches, an alternative model, where the dark force mediator is an hypothetical leptophobic B boson, is exploited in the $\phi$ decay to $\eta$-B where B will decay in $\pi^0\gamma$.

Moreover, KLOE-2 has the possibility to investigate $\pi^0$ production from $\gamma \gamma$ fusion thanks to two scintillator hodoscopes installed in the DA$\Phi$NE beam pipe to tag final-state leptons from $e^+e^- \to \gamma^{\ast}\gamma^{\ast}e^+e^-\to \pi^0 e^+e^-$ . The aim is to perform the high precision measurement of the $\pi^0$ width to test low-energy QCD dynamics. The status of the $\gamma^{\ast}\gamma^{\ast}\to \pi^0$ analysis will be reported.

KLOE-2 searches also the
$\phi\rightarrow \eta\, \pi^+ \pi^- ,\,\mu^+\mu^-$ decays with $\eta\rightarrow\gamma \gamma$ and $\eta \to 3\pi^0$. $\phi\rightarrow \eta \pi^+ \pi^- $ is double suppressed by G−parity and the OZI rule, with an expected BR around $0.35\times 10^{−6}$, while for the $\phi\rightarrow \eta \mu^+\mu^-$ decay an upper limit was set as $0.94\times10^{−5}$. By analyzing those decays with KLOE/KLOE-2 data clear signals are seen for the first time.

Collaboration / Activity KLOE-2 collaboration

Primary authors

Giuseppe Mandaglio (University of Messina) Cao Bo (Uppsala University)

Presentation Materials