Disentangling Higgs-top couplings in associated production

In the presence of CP violation, the Higgs-top coupling may have both scalar and pseudoscalar components, κ t and ${{\widetilde{\kappa}}_t}$ , which are bounded indirectly but only weakly by the present experimental constraints on the Higgs-gluon-gluon and Higgs-γ-γ couplings, whereas upper limits on electric dipole moments provide strong additional indirect constraints on ${{\widetilde{\kappa}}_t}$ , if the Higgs-electron coupling is similar to that in the Standard Model and there are no cancellations with other contributions. We discuss methods to measure directly the scalar and pseudoscalar Higgs-top couplings by measurements of Higgs production in association with $\overline{t}t$ , single t and single $\overline{t}$ at the LHC. Measurements of the total cross sections are very sensitive to variations in the Higgs-top couplings that are consistent with the present indirect constraints, as are invariant mass distributions in $\overline{t}tH$ , tH and $\overline{t}H$ final states. We also investigate the additional information on κ t and ${{\widetilde{\kappa}}_t}$ that could be obtained from measurements of the longitudinal and transverse t polarization in the different associated production channels, and the $\overline{t}t$ spin correlation in $\overline{t}tH$ events

Buckets of Higgs and tops

We show that associated production of a Higgs with a top pair can be observed in purely hadronic decays. Reconstructing the top quarks in the form of jet buckets allows us to control QCD backgrounds as well as signal combinatorics. The background can be measured from side bands in the reconstructed Higgs mass. We back up our claims with a detailed study of the QCD event simulation, both for the signal and for the backgrounds

Muon g-2 and LHC phenomenology in the L μ − L τ gauge symmetric model

In this paper, we consider phenomenology of a model with an L μ − L τ gauge symmetry. Since the muon couples to the L μ − L τ gauge boson (called Z ″ boson), its contribution to the muon anomalous magnetic moment (muon g-2) can account for the discrepancy between the standard model prediction and the experimental measurements. On the other hand, the Z ″ boson does not interact with the electron and quarks, and hence there are no strong constraints from collider experiments even if the Z ″ boson mass is of the order of the electroweak scale. We show an allowed region of a parameter space in the L μ − L τ symmetric model, taking into account consistency with the electroweak precision measurements as well as the muon g-2. We study the Large Hadron Collider (LHC) phenomenology, and show that the current and future data would probe the interesting parameter space for this model