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Walker, Joel W.

Publications and source records attributed to Walker, Joel W..

10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Probing squeezed bino-slepton spectra with the Large Hadron Collider

In this study, we consider a minimal supersymmetric Standard Model scenario in which the only light superparticles are a binolike dark matter candidate and a nearly degenerate slepton. It is notoriously difficult to probe this scenario at the Large Hadron Collider (LHC), because the slepton pair-production process yields a final state with soft leptons and small missing transverse energy. We study this scenario in the region of parameter space where the mass difference between the lightest neutralino and the lightest slepton ( Δ m ) is ≲ 60 GeV , focusing on the process in which an additional radiated jet provides a transverse boost to the slepton pair. We then utilize the angular separation of the leptons from each other and from the missing transverse energy, as well as the angular separation between the jet and the missing transverse energy, to distinguish signal from background events. We also use the reconstructed ditau mass, the cos θ ℓ 1 ℓ 2 * variable, and for larger Δ m , a lower bound on the lepton p T . These cuts can dramatically improve both signal sensitivity and the signal-to-background ratio, permitting discovery at the LHC with reasonable integrated luminosity over the interesting region of parameter space. Using our search strategy the LHC will be able to exclude m μ ˜ ≈ 200 GeV for Δ m ≲ 60 GeV at 1.5 – 3 σ with 1000 fb - 1 of integrated luminosity. Although we focus on a particular model, the results generalize to a variety of scenarios in which the dark matter and a leptonic partner are nearly degenerate in mass, and especially to scenarios featuring a scalar mediator.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Probing the Goldstone equivalence theorem in heavy weak doublet decays

We explore here the decays from heavy Higgsino-like weak doublets into Z , h bosons and missing particles. When pair-produced at the LHC, the subsequent Z , h → ℓ ℓ , b b ¯ decays in the doublet decay cascade can yield 4 ℓ , 2 ℓ 2 b and 4 b + E T + j ( s ) final states. Mutual observation of any two of these channels would provide information on the associated doublets’ decay branching fractions into a Z or h , thereby probing the Goldstone equivalence relation, shedding additional light on the Higgs sector of beyond the Standard Model theories and facilitating the discrimination of various contending models, in turn. We compare the Z / h decay ratio expected in the minimal supersymmetric model, the next-to-minimal supersymmetric model (NMSSM)and a minimal singlet-doublet dark matter model. Furthermore, we conduct a full Monte Carlo analysis of the prospects for detecting the targeted final states during 14 TeV running of the LHC in the context of a representative NMSSM benchmark model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗