  Ultralight bosons are predicted in many extensions to the Standard Model and
are popular dark matter candidates. The black hole superradiance mechanism
allows for these particles to be probed using only their gravitational
interaction. In this scenario, an ultralight boson cloud may form spontaneously
around a spinning black hole and extract a non-negligible fraction of the black
hole's mass. These oscillating clouds produce quasi-monochromatic,
long-duration gravitational waves that may be detectable by ground-based or
space-based gravitational wave detectors. We discuss the capability of a new
long-duration signal tracking method, based on a hidden Markov model, to detect
gravitational wave signals generated by ultralight vector boson clouds,
including cases where the signal frequency evolution timescale is much shorter
than that of a typical continuous wave signal. We quantify the detection
horizon distances for vector boson clouds with current- and next-generation
ground-based detectors. We demonstrate that vector clouds hosted by black holes
with mass $\gtrsim 60 M_{\odot}$ and spin $\gtrsim 0.6$ are within the reach of
current-generation detectors up to a luminosity distance of $\sim 1$ Gpc. This
search method enables one to target vector boson clouds around remnant black
holes from compact binary mergers detected by gravitational-wave detectors. We
discuss the impact of the sky localization of the merger events and demonstrate
that a typical remnant black hole reasonably well-localized by the current
generation detector network is accessible in a follow-up search.
