Object-based missing transverse momentum significance in the ATLAS detector

Missing transverse momentum, $E_{\rm T}^{\rm miss}$, is commonly used to study the production of weakly interacting particles. The missing transverse momentum significance, $\mathcal{S}$, helps to separate events in which the reconstructed ${E_{\rm T}^{\rm miss}}$ originates from weakly interacting particles, from those in which ${E_{\rm T}^{\rm miss}}$ is consistent with contributions coming from particle measurement, resolutions and inefficiencies. On an event-by-event basis, $\mathcal{S}$ evaluates the p-value that the observed ${E_{\rm T}^{\rm miss}}$ is consistent with the null hypothesis of zero real ${E_{\rm T}^{\rm miss}}$, given the full event composition. A high value of $\mathcal{S}$ is an indication that the ${E_{\rm T}^{\rm miss}}$ observed in the event is not well explained by resolution smearing alone, implying that the event is more likely to contain unseen objects such as neutrinos or more exotic weakly interacting particles. A new definition of an object-based missing transverse momentum significance variable is presented. Its performance is studied in $Z \rightarrow e e$ and $ZZ \rightarrow e e \nu \nu$ events using data collected in proton–proton collisions at a centre-of-mass energy of $13$ TeV during 2015 and 2016. Results are shown for a data sample corresponding to an integrated luminosity of $36\,\rm{fb}^{-1}$.