"Model-independent upper cross section limit" of "Search for new physics in the $\tau$ lepton plus missing transverse momentum final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV"

Bayesian 95% CL model-independent upper limit on the product of signal cross sections and branching fraction for the $\tau+\nu$ decay for a back-to-back $\tau$ lepton plus $p_{T}^{miss}$ topology.
To calculate this limit, all events for signal, background, and data are summed starting from a minimum $m_{T}$ threshold
and then divided by the total number of events. No assumption on signal shape is included in this limit. The expected
(dashed line) and observed (solid line) limits are shown as well as the 68% and 95% CL uncertainty bands (green and yellow, respectively).