LHC searches for dark sector showers

Abstract

This paper proposes a new search program for dark sector parton showers at the Large Hadron Collider (LHC). These signatures arise in theories characterized by strong dynamics in a hidden sector, such as Hidden Valley models. A dark parton shower can be composed of both invisible dark matter particles as well as dark sector states that decay to Standard Model particles via a portal. The focus here is on the specific case of 'semi-visible jets,' jet-like collider objects where the visible states in the shower are Standard Model hadrons. We present a Simplified Modellike parametrization for the LHC observables and propose targeted inclusive search strategies for regions of parameter space that are not covered by existing analyses. Following the 'mono-X' literature, the portal is modeled using either an effective field theoretic contact operator approach or with one of two ultraviolet completions; sensitivity projections are provided for all three cases. We additionally highlight that the LHC has a unique advantage over direct detection experiments in the search for this class of dark matter theories. arXiv:1707.05326v2 [hep-ph]

Strongly interacting dark sectors in the early Universe and at the LHC through a simplified portal

“…We finally note that, following Ref. [22], the sensitivity estimate shown in figure 6 can be treated as prompt. Jets originating from displaced vertices would likely be rejected in such an analysis, which would reduce the sensitivity slightly compared to what is shown in figure 6.…”

“…We then apply the same cuts as in Ref. [22]. At the preselection level, these require / E T > 200 GeV and at least two jets with p T > 100 GeV and |η| < 2.4.…”

“…For comparison, we also show the background estimate obtained in Ref. [22] rescaled to L = 300 fb −1 . One can clearly see the difference in shape between signal and background arising from the fact that M T ≤ m Z for the decay of an on-shell Z .…”

“…Relatively weak interactions are sufficient for the ρ 0 decays to proceed sufficiently fast to keep the dark sector in thermal equilibrium with the SM during freeze-out, while somewhat stronger interactions allow for the dark sector to be probed with direct detection experiments and at the LHC. Rho mesons that decay promptly on collider scales as well as long-lived mesons are a generic possibility of these models, leading to a wide range of novel collider signatures, such as semi-visible jets [21][22][23] and emerging jets [16,24].…”

Classification of dark pion multiplets as dark matter candidates and collider phenomenology

“…Generically, both stable and unstable dark pions can be produced in a parton shower. Assuming the unstable pions decay hadronically, this will result in the production of semivisible jets [17,59,60]. These roughly look like generic jets, but are accompanied by collinear stable particles that escape the detector and contribute to the missing transverse energy (MET).…”