The first search for a heavy charged vector boson in the final state with a tau lepton and a neutrino is reported, using 19.7 fb −1 of LHC data at √ s = 8 TeV. A signal would appear as an excess of events with high transverse mass, where the standard model background is low. No excess is observed. Limits are set on a model in which the W decays preferentially to fermions of the third generation. These results substantially extend previous constraints on this model. Masses below 2.0 to 2.7 TeV are excluded, depending on the model parameters. In addition, the existence of a W boson with universal fermion couplings is excluded at 95% confidence level, for W masses below 2.7 TeV. For further reinterpretation a model-independent limit on potential signals for various transverse mass thresholds is also presented.

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Abstract:We investigate spin correlation effects in the "antler" event topology pp → A(A * ) → B 1 B 2 → (ℓ − C 1 )(ℓ + C 2 ) at the LHC. We study the shapes of several kinematic variables, including the relative pseudorapidity, relative azimuthal angle and the energies of the two leptons, as well as several mass variables M ℓℓ , M eff , √ s min , M T 2 , M CT and M CTx . We focus on the two kinematic extremes of √ s -threshold and infinity -and derive analytical expressions for the differential distributions of several variables, most notably the cos θ * ℓ − ℓ + variable proposed by Barr in hep-ph/0511115. For all possible spin assignments of particles A, B and C, we derive the cos θ * ℓ − ℓ + differential distribution at threshold, including the effects of spin correlations. Our analytical results help identify the problematic cases for spin discrimination.

An important tool for interpreting LHC searches for new physics are simplified models. They are characterized by a small number of parameters and thus often rely on a simplified description of particle production and decay dynamics. Considering the production of squarks of the first two generations we compare the interpretation of current LHC searches for hadronic jets plus missing energy signatures within simplified models with the interpretation within a complete supersymmetric model. Although we find sizable differences in the signal efficiencies, in particular for large supersymmetric particle masses, the differences between the mass limits derived from a simplified model and from the complete supersymmetric model are moderate given the current LHC sensitivity. We conclude that simplified models provide a reliable tool to interpret the current hadronic jets plus missing energy searches at the LHC in a more model-independent way.

Simplified models are an important tool for the interpretation of searches for new physics at the LHC. They are defined by a small number of new particles together with a specific production and decay pattern. The simplified models adopted in the experimental analyses thus far have been derived from supersymmetric theories, and they have been used to set limits on supersymmetric particle masses. We investigate the applicability of such simplified supersymmetric models to a wider class of new physics scenarios, in particular those with same-spin Standard Model partners. We focus on the pair production of quark partners and analyze searches for jets and missing energy within a simplified supersymmetric model with scalar quarks and a simplified model with spin-1/2 quark partners. Despite sizable differences in the detection efficiencies due to the spin of the new particles, the limits on particle masses are found to be rather similar. We conclude that the supersymmetric simplified models employed in current experimental analyses also provide a reliable tool to constrain same-spin BSM scenarios.