Search for dark matter produced in association with a leptonically decaying $${\mathrm{Z}} $$ boson in proton–proton collisions at $$\sqrt{s}=13\,\text {Te}\text {V} $$

Abstract

A search for dark matter particles is performed using events with a Z boson candidate and large missing transverse momentum. The analysis is based on proton–proton collision data at a center-of-mass energy of 13$$\,\text {Te}\text {V}$$ Te , collected by the CMS experiment at the LHC in 2016–2018, corresponding to an integrated luminosity of 137$$\,\text {fb}^{-1}$$ fb - 1 . The search uses the decay channels $${\mathrm{Z}} \rightarrow {\mathrm{e}} {\mathrm{e}} $$ Z → e e and $${\mathrm{Z}} \rightarrow {{\upmu }{}{}} {{\upmu }{}{}} $$ Z → μ μ . No significant excess of events is observed over the background expected from the standard model. Limits are set on dark matter particle production in the context of simplified models with vector, axial-vector, scalar, and pseudoscalar mediators, as well as on a two-Higgs-doublet model with an additional pseudoscalar mediator. In addition, limits are provided for spin-dependent and spin-independent scattering cross sections and are compared to those from direct-detection experiments. The results are also interpreted in the context of models of invisible Higgs boson decays, unparticles, and large extra dimensions.

Benchmarking LHC searches for light 2HDM+$\boldsymbol{a}$ pseudoscalars

“…Since for models with pseudoscalar mediators the DM direct detection (DD) constraints are weaker compared to models with scalar mediators, such models are more attractive from an astrophysical point of view since they often allow to reproduce the observed DM relic abundance in a wider parameter space and with less tuning. These features admit a host of missing transverse momentum (E miss T ) signatures at colliders which can be consistently compared and combined, making the 2HDM+a model one of the pillars of the LHC DM search programme [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

“…It is therefore questionable if one can find a 2HDM+a type-II model realisation that can explain the a µ anomaly and survive the existing LHC constraints from non-SM Higgs production. Notice that in the case of a lepto-specific 2HDM+a model of type-X the latter conclusion does not hold and addressing (15) is possible in the 2HDM+a context [73].…”

“…Figure 2: As Figure 1 but for the 2HDM+a benchmark II scenario(10). Parameter choices inside the yellow dash-dotted vertical band shown in the right panel allow to accommodated the excess(15) observed in a µ at the 95% CL. For additional explanations consult main text.…”

Searches for invisible Higgs decays at the LHC

“…In addition, the characteristic features of the lepton pair are potent handles for effective background rejection. In the currently strongest result in this channel [9], the CMS Collaboration analyzes a data set corresponding to 137 fb −1 . Events are selected that contain a same-…”

Searching for Dark Matter through Vector Boson Fusion Topology at the LHC

“…Therefore some other particle needs to be produced with DM in order to have some observable in the ATLAS or CMS experiments. Several final states have been already explored in the LHC, for example DM production in association with jets [4], or DM production with a leptonically decaying Z boson [5], or DM produced along with a Higgs boson [6]. However, the correct and most general modelling of DM production at colliders has remained a big challenge and different approaches have been developed.…”