Search for dark forces with KLOE

Institute of Physics, Jagiellonian University, ul. Łojasiewicza 11, 30-348 Cracow, Poland

^* e-mail: aleksander.gajos@doctoral.uj.edu.pl

Published online: 29 November 2016

Abstract

During the last years several Dark Sector Models have been proposed in order to address striking astrophysical observations which failed standard interpretations. In the minimal case a new vector particle, the so called dark photon, or A′ or U boson, is introduced, with small coupling with Standard Model particles. Also, the existence of a dark Higgs boson h′ is postulated, in analogy with the Standard Model, to give mass to the U boson through the Spontaneous Symmetry Breaking mechanism. The KLOE experiment working at DAΦNE, an e⁺e⁻ collider operating in Frascati (near Rome), searched for the existence of the U boson investigating three different processes and six different final states: (1) in Dalitz decays of the ϕ meson ϕ → ηU, with U → e⁺e⁻ and η → π⁺π⁻π⁰ and π⁰π⁰π⁰, (2) in e⁺e⁻ → Uh′ events, with U decaying into lepton and pion pairs, (3) in the dark Higgsstrahlung process, e⁺e⁻ → Uh′, U → μ⁺μ⁻, h′ invisible. Limits on the model parameters have been set at 90 % CL for U boson masses below 1 GeV. Further improvements are expected in terms of sensitivity and discovery potential with the new KLOE-2 detector.