Detecting a relic background of scalar waves with LIGO

We discuss the possible detection of a stochastic background of massive, nonrelativistic scalar particles through the cross correlation of the two LIGO interferometers in the initial, enhanced, and advanced configuration. If the frequency corresponding to the mass of the scalar field lies in the detector sensitivity band, and the nonrelativistic branch of the spectrum gives a significant contribution to energy density required to close the Universe, we find that the scalar background can induce a non-negligible signal in competition with a possible signal produced by a stochastic background of gravitational radiation.