Gravitational-wave (GW) observations provide unique information about compact objects. As detector sensitivity increases, new astrophysical sources of GWs could emerge. Close hyperbolic encounters are one such source class: Scattering of stellar mass compact objects is expected to manifest as GW burst signals in the frequency band of current detectors. We present the search for GWs from hyperbolic encounters in the second half of the third Advanced LIGO-Virgo observing run (O3b). We perform a model-informed search with a machine-learning enhanced Coherent WaveBurst algorithm. No significant event has been identified in addition to known detections of compact binary coalescences. We inject in the O3b data nonspinning third post-Newtonian order accurate hyperbolic encounter model with component masses between [2,100]M⊙, impact parameter in [60,100]GM/c2, and eccentricity in [1.05, 1.6]. We further discuss the properties of the simulation recovered. For the first time, we report the sensitivity volume achieved for such sources, which for O3b data reaches up to 3.9±1.4×105 Mpc3 yr for compact objects with masses in the range [20,40]M⊙, corresponding to a rate density upper limit of 0.589±0.094×10-5 Mpc-3 yr-1. Finally, we present a projected sensitive volume for the next observing runs of current detectors, namely, O4 and O5.
