PHELEX—Present Status

This paper presents the results of measurements of diurnal variations in the single electron count rate arising from dark photon conversion at the cathode of a gas proportional counter. Three experimental series were conducted, each consisting of 4 runs lasting approximately 60 days per run. One can expect an excess in the single electron count rate above the average level if the polarization vector of dark photons in the region traversed by the Sun forms an angle between $$20^{\circ}$$ and $$50^{\circ}$$ with the Earth’s rotational axis. Such an effect was observed in the first series (significance $$6\sigma$$ ) and the second series (significance $$4\sigma$$ ). However, in the third series, which employed two identical detectors simultaneously, the effect was not observed on either detector. This result practically excludes the possibility that the effect observed earlier was purely instrumental. The results of the three series may be interpreted as a possible effect arising from the Sun’s passage through regions of dark matter characterized by different orientations of the dark photon polarization vector.