  Central jet vetoes are powerful tools for reducing QCD background in
measurements and searches for electroweak and colorless, new physics processes
in hadron collisions. In this letter, we report the key findings of a new
philosophy to designing searches for such phenomena at hadron colliders, one
designed and centered around a dynamical jet veto instead a static veto applied
independently of other selection criteria. Specifically, we investigate the
theoretical and phenomenological consequences of setting the jet veto scale to
the transverse momentum $(p_T)$ of the leading charged lepton $\ell$ in
multi-lepton processes on an event-by-event basis. We consider the case of a
TeV-scale heavy neutrino $N$ decaying to the trilepton final state and find the
following: (i) Perturbative uncertainties associated with the veto greatly
reduce due to tying the veto scale to the hard process scale. (ii) The signal
efficiency for passing the veto jumps to $\gtrsim95\%$ and exhibits
little-to-no dependence on the neutrino mass scale. (iii) Top quark and `fake'
lepton rejection capabilities also improve compared to only vetoing heavy
flavor-tagged jets above a fixed $p_T$. This results in an increased
sensitivity to active-sterile neutrino mixing by approximately an order of
magnitude over the LHC's lifetime. For a Dirac neutrino with mass $m_N =
150-1000$ GeV and the representative active-sterile mixing hypothesis $\vert
V_{e4}\vert = \vert V_{\tau 4}\vert$ with $\vert V_{\mu 4}\vert=0$, we find
that LHC experiments can probe $\vert V_{e4}\vert^2, \vert V_{\tau 4}\vert^2
\lesssim 6\times10^{-4} - 8\times10^{-3}$, surpassing the global upper limit
for $m_N < 450$ GeV, with $\mathcal{L}=3$ ab$^{-1}$ of data at $\sqrt{s}=14$
TeV. Due to the color structures of the heavy $N$ production mechanisms
considered, we argue that our results hold broadly for other color-singlet
processes.
