  The top quark mass plays a central role in our understanding of the Standard
Model and its extrapolation to high energies. However, precision measurements
of the top quark mass at hadron colliders are notoriously difficult, motivating
the development of qualitatively new approaches to take advantage of the
enormous datasets of top quarks at the Large Hadron Collider (LHC). Recent
advances in jet substructure have enabled the precise theoretical description
of angular correlations in energy flux. However, their application to precision
mass measurements is less direct since they measure a dimensionless angular
scale. Inspired by the use of standard candles in cosmology, we introduce a
single energy correlator-based observable that reflects the characteristic
angular scales of both the $W$-boson and the top quark masses. This gives
direct access to the dimensionless quantity $m_{t}/m_{W}$, from which $m_{t}$
can be extracted in a well-defined short-distance mass scheme as a function of
the well-known $m_{W}$ (our LHC Cepheid variable). We perform a
Monte-Carlo-based study to demonstrate the properties of our observable and the
statistical feasibility of its extraction from the Run 2 and 3 and
High-Luminosity LHC data sets. The resulting $m_t$ has remarkably small
uncertainties from non-perturbative effects and is insensitive to the parton
distribution functions. We believe that our proposed observable provides a road
map for a rich program to achieve a record precision top quark mass measurement
at the LHC.
