Global analysis of dark matter simplified models with leptophobic spin-one mediators using MasterCode

We report the results of a global analysis of dark matter simplified models (DMSMs) with leptophobic mediator particles of spin one, considering the cases of both vector and axial-vector interactions with dark matter (DM) particles and quarks. We require the DMSMs to provide all the cosmological DM density indicated by Planck and other observations, and we impose the upper limits on spin-independent and -dependent scattering from direct DM search experiments. We also impose all relevant LHC constraints from searches for monojet events and measurements of the dijet mass spectrum. We model the likelihood functions for all the constraints and combine them within the framework, and probe the full DMSM parameter spaces by scanning over the mediator and DM masses and couplings, not fixing any of the model parameters. We find, in general, two allowed regions of the parameter spaces: one in which the mediator couplings to Standard Model (SM) and DM particles may be comparable to those in the SM and the cosmological DM density is reached via resonant annihilation, and one in which the mediator couplings to quarks are $$\lesssim \, 10^{-3}$$≲10-3 and DM annihilation is non-resonant. We find that the DM and mediator masses may well lie within the ranges accessible to LHC experiments. We also present predictions for spin-independent and -dependent DM scattering, and present specific results for ranges of the DM couplings that may be favoured in ultraviolet completions of the DMSMs.

Measurement of Z → bb̄ cross section and search for a Higgslike particle produced in association with b quarks at CDF

We present a measurement of the Z → bb̄ production cross section in pp collisions at √s = 1.96 TeV . We use a data set of 5.46 fb-1 collected by the CDF experiment at the Tevatron collider during Run II using a dedicated trigger path which required a displaced vertex compatible with a b-hadron decay. A data-driven procedure is applied to estimate the dijet mass spectrum of the non-resonant multijet background. Using a similar strategy we set one of the most stringent upper limits on the production of a Higgs-like particle in association with b quarks. We also set a limit on the inclusive SM H → bb̄.

Resonance contribution of scalar color octet to tt̄ production at the LHC in the minimal four-color quark–lepton symmetry model

The scalar color octet contribution to the resonance [Formula: see text]-pair production at the LHC is calculated and analyzed by taking into account the one-loop effective two-gluon vertex. It is shown that this contribution from the scalar color octet [Formula: see text] predicted by the minimal model with the four-color quark–lepton symmetry is for [Formula: see text] = 13 TeV of about a few percent for 750 [Formula: see text] 1800 GeV and can exceed 10% for 400 [Formula: see text] 750 GeV. It is also pointed out that the search for the scalar octet [Formula: see text] as the resonance in the dijet mass spectra seems to be difficult because of the smallness of its one-loop effective two-gluon interaction.