102775516
Study of signal and background conditions in t anti-t H, H ---> WW(*) and WH, H ---> WW(*)
73584702
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at $$\sqrt{s}=8~$$s=8TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb$${}^{-1}$$-1 of $$\sqrt{s}=8$$s=8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with $$p_{\mathrm {T}}> 120$$pT>120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between $$E_{\mathrm {T}}^{\mathrm {miss}}>150$$ETmiss>150 GeV and $$E_{\mathrm {T}}^{\mathrm {miss}}> 700$$ETmiss>700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.
18125809
Heavy octets and Tevatron signals with three or four b jets
Hypothetical color-octet particles of spin 0, pair-produced at hadron colliders through their QCD coupling, may lead to final states involving three or four b jets. The scalar octets may also be resonantly produced in pairs via a spin-1 octet, as we show within a renormalizable coloron model. We analyze kinematic distributions of the 3b final state that differentiate between these two production mechanisms, as well as between scalar octets and supersymmetric Higgs bosons. A scalar octet of mass in the 140–150 GeV range can explain the nonstandard shape of the b-jet transverse energy distributions reported by the CDF Collaboration, especially when the coloron mass is slightly above twice the scalar mass. The dominant decay mode of the scalar octet in that case is into a pair of gluons, so that the production of a pair of dijet resonances is large in this model, of about 40 pb at the Tevatron. Even when a W boson is radiated from the initial state, the inclusive cross section for producing a dijet resonance near the scalar octet mass remains sizable, around 0.15 pb.
119113952
Stop the top background of the stop search
A bstractThe main background for the supersymmetric stop direct production search comes from Standard Model $ t\overline t $ events. For the single-lepton search channel, we introduce a few kinematic variables to further suppress this background by focusing on its dileptonic and semileptonic topologies. All are defined to have end points in the background, but not signal distributions. They can substantially improve the stop signal significance and mass reach when combined with traditional kinematic variables such as the total missing transverse energy. Among them, our variable $ M_{{T2}}^W $ hasthebestoverallperformancebecause it uses all available kinematic information, including the on-shell mass of both W’s. We see 20 %-30 % improvement on the discovery significance and estimate that the 8 TeV LHC run with 20 fb−1 of data would be able to reach an exclusion limit of 650-700 GeV for direct stop production, as long as the stop decays dominantly to the top quark and a light stable neutralino. Most of the mass range required for the supersymmetric solution of the naturalness problem in the standard scenario can be covered.