Hunting for neutral, long-lived exotica at the LHC using a missing transverse energy signature

Searches at the Large Hadron Collider (LHC) for neutral, long-lived particles have historically relied on the detection of displaced particles produced by their decay within the detector volume. In this paper we study the potential of the complementary signature comprising of the missing transverse energy (ETmiss) signal, traditionally used to look for dark matter, e.g., the lightest supersymmetric particle (LSP), to extend the LHC coverage to models with long-lived (LL) particles when they decay outside the detector. Using CMS and ATLAS analyses at the 8 TeV LHC, we set an upper limit at the 95% confidence level (CL) on the production cross sections for two specific scenarios: (i) a model with a heavy non-standard model Higgs boson decaying to a LL scalar and (ii) an R-parity violating RPV SUSY model with a LL neutralino. We show that this method can significantly extend the LHC sensitivity to neutral, LL particles with arbitrary large lifetimes and that the limits obtained from a ETmiss signal are comparable to those from displaced particle searches for decay distances above a few meters. Results obtained in this study do not not depend on the specific decay channel of the LL particle and therefore are model-independent in this sense. We provide limits for the whole two-dimensional plane in terms of the mass of the LL particle and the mass of the mediator up to masses of 2 TeV including particular benchmarks studied in the original experimental papers. We have made these limits available in the form of a grid which can be used for the interpretation of various other new physics models