Abstract: The existence of a new vector boson has been postulated in different scenarios where the coupling to the SM can be achieved either via a kinetic mixing term, the U boson, or by coupling to the baryon number, the B boson. Direct searches for these dark matter mediators are performed at accelerator facilities. The KLOE detector at the DANE Φ-factory has been prolific in searches for the U boson in both Dalitz decays of the  meson, →ηU with U→e+e-, and continuum events, e+e-→Uγ. For all of these processes, an upper limit for the U boson coupling ε2 of 10-7 to 10-5 has been established in the mass range 4 MeV·c-2

Key words: dark matter, dark forces, U boson, A′, dark Higgsstrahlung, h′, upper limit