Abbott, B PAbbott, RAbbott, T DAbernathy, M RAcernese, FAckley, KAdams, CAdams, TAddesso, PAdhikari, Rana XAltin, PaulChow, JongMansell, GeorgiaMcClelland, DavidMcManus, DavidMcRae, TerryNguyen, ThanhRabeling, DavidScott, SusanShaddock, DanielSlagmolen, BramWard, RobertYap, Min Jet2023-11-282023-11-280031-9007http://hdl.handle.net/1885/307480A wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. Following the observations of GW150914 and GW151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. As a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. We perform a search for the isotropic stochastic gravitational-wave background using data from Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. The data display no evidence of a stochastic gravitational-wave signal. We constrain the dimensionless energy density of gravitational waves to be Ω0<1.7×10-7 with 95% confidence, assuming a flat energy density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This is a factor of ∼33 times more sensitive than previous measurements. We also constrain arbitrary power-law spectra. Finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background.application/pdfen-AU© 2017 The authors201710.1103/PhysRevLett.118.1211012022-08-21