Latest results from KLOE-2

Abstract

Abstract. The KLOE experiment at the Frascati φ-factory recently obtained results on i) CPT and Lorentz invariance tests from the study of quantum interference of the neutral kaon pairs; ii) precision measurement of the branching fraction, BR(00025 syst , and iii) on dark photon searches with the analysis of the e + e − → μμγ final state. We have also studied the transition form factors of the φ meson to the pseudoscalars, π 0 and η, that is presented in a separate contribution to this volume. The KLOE experimentThe KLOE experiment at the Frascati φ-factory took most of the data in 2004-2006, with 2.5 fb −1 of integrated luminosity at the φ peak, and about 250 pb −1 at 1 GeV, 20 MeV below the resonance, for the study of di-pion and di-lepton production, and γ-γ interactions. In year 2013 we successfully completed the installation of the detector upgrades, and the DAΦNE accelerator underwent a massive renovation to improve instantaneous luminosity and operation reliability.The KLOE detector consists of a large cylindrical Drift Chamber (DC), surrounded by a leadscintillating fiber electromagnetic calorimeter (EMC), all embedded inside a superconducting coil, providing a 0.52 T axial field. The drift chamber [1], 4 m in diameter and 3.3 m long, has 12,582 all-stereo tungsten sense wires with a shell made of carbon fiber-epoxy composite. The momentum resolution is σ(p ⊥ )/p ⊥ ∼ 0.4%. The calorimeter [2] covers 98% of the solid angle. Each cell is read out at both ends by photomultipliers, both in amplitude and time. Energy and time resolutions are σ E /E = 5.7%/ √ E (GeV) and σ t = 57 ps/ √ E (GeV) ⊕ 100 ps. The detector has been upgraded i) to improve vertex reconstruction near the beam interaction region (IR), ii) to increase the acceptance for low polar angle photons, and iii) to reconstruct particles passing through the DAΦNE final focusing region. A cylindrical tracking chamber based on the Gaseous Electron Multiplier (GEM) technology [3], the first cylindrical 3-GEM detector ever built, has been installed between the beam pipe and the big Drift Chamber to track particles closer to their origin; two small stations of LYSO calorimeters [4] have been placed on the beam pipe for the detection of low polar angle photons; the final focusing region has been instrumented with sampling calorimeters done by five layers of tungsten interleaved with scintillator tiles coupled to fibers that are readout on one side by silicon photomultipliers [5]. A new data taking campaign aiming to collect O(10) fb −1 in 2-3 years of data taking is planned to extend the experimental program in kaon/hadron physics and on dark photon searches [6]. a