Pixel tracklets, disappearing tracks reconstructed with only pixel hits, have proven to be a promising technique in LHC analyses to search for dark matter candidates at the LHC that belong to a nearly-degenerate electroweak multiplet. However, a Pseudo-Dirac electroweak doublet fermion, arguably the most interesting such possibility, has a shorter lifetime and therefore existing tracklet searches are less sensitive in this case. We assess the performance of a tracklet search optimized for shorter lifetimes by requiring only three pixel hits for the tracklet reconstruction, and by demanding an accompanying soft track for suppressing backgrounds. We estimate how far the sensitivity of existing searches can be extended into the region of parameter space with this optimized search.

United States

Matthew Gignac

Can Kilic

Croatia

Rakhi Mahbubani

Taewook Youn

Optimizing pixel tracklet searches for shorter lifetimes

Dark matter can form bound states upon the emission of quanta of energy equal to the binding energy. The rate of this process is large for strongly interacting dark matter, and further enhanced by long-distance effects. The resulting monochromatic and diffuse <math><mi>γ</mi></math> rays can be tested in indirect-detection experiments. If dark matter has electroweak charge, indirect signals include multiple observable photon lines for masses in the TeV range. Otherwise, if it couples only via a dark photon portal, diffuse spectra from dwarf galaxies and cosmic microwave background reionization set powerful limits for masses below a tera-electron volt. This mechanism provides a powerful means of probing asymmetric dark matter today.

CERN

Italy

Michele Redi

Andrea Tesi

Indirect detection of composite asymmetric dark matter

We examine the sensitivity at a future 100 TeV proton-proton collider to compressed dark sectors whose decay products are invisible due to below-threshold energies and/or small couplings to the Standard Model. Such a scenario could be relevant to models of WIMP dark matter, where the lightest New Physics state is an (isolated) electroweak multiplet whose lowest component is stable on collider timescales. We rely on the additional emission of a hard on-shell Z-boson decaying to leptons, a channel with low background systematics, and include a careful estimate of the real and fake backgrounds to this process in our analysis. We show that an integrated luminosity of 30 ab−1 would allow exclusion of a TeV-scale compressed dark sector with inclusive production cross section 0.3 fb, for 1% background systematic uncertainty and splittings below 5 GeV. This translates to exclusion of a pure higgsino (wino) multiplet with mass of 500 (970) GeV.

Switzerland

Germany

José Zurita

Probing compressed dark sectors at 100 TeV in the dileptonic mono-Z channel

Pedro Schwaller

Erratum to: Closing the window for compressed dark sectors with disappearing charged tracks

We investigate the sensitivity at current and future hadron colliders to a heavy electrically-charged particle with a proper decay length below a centimetre, whose decay products are invisible due to below-threshold energies and/or small couplings to the Standard Model. A cosmologically-motivated example of a framework that contains such a particle is the Minimal Supersymmetric Standard Model in the limit of pure Higgsinos. The current hadron-collider search strategy has no sensitivity to the upper range of pure-Higgsino masses that are consistent with the thermal relic density, even at a future collider with 100 TeV centre-of-mass energy. We show that performing a disappearing track search within the inner 10 cm of detector volume would improve the reach in lifetime by a factor of 3 at the 14 TeV LHC and a further factor of 5 at a 100 TeV collider, resulting in around 10 events for 1.1 TeV thermal Higgsinos. In order to include the particles with the largest boost in the analysis, we furthermore propose a purely track-based search in both the central and forward regions, each of which would increase the number of events by another factor of 5, improving our reach at small lifetimes. This would allow us to definitively discover or exclude the experimentally-elusive pure-Higgsino thermal relic at a 100 TeV collider. Our results illustrate the importance of varying detector design when assessing the reach of future high energy colliders.

Closing the window for compressed dark sectors with disappearing charged tracks

We explore the sensitivity of the LHC at 14 TeV centre-of-mass energy (LHC14) to the single production and decay of top-antitop resonances in the four-top final state. We focus on the same-sign dilepton channel, and work within a simplified model with a vector boson coupling to the Standard Model only via its interactions with right-handed top quarks. We find it is possible to discover (exclude) such a vector boson with 300 fb −1 of integrated luminosity up to a mass of 1.2 (1.6) TeV for a modest coupling to tops of g ρ = 2. We present our results as an exclusion limit on the cross-section × branching ratio for ease of recasting, and interpret them in the context of the gauge-singlet vector boson ρ X present in many simple Composite Higgs theories.

China

Da Liu

Probing top-antitop resonances with t t ¯ $$ t\overline{t} $$ scattering at LHC14