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

Sharpening m T 2 cusps: the mass determination of semi-invisibly decaying particles from a resonance

We revisit mass determination techniques for the minimum symmetric event topology, namely X pair production followed by X → ℓN , where X and N are unknown particles with the masses to be measured, and N is an invisible particle, concentrating on the case where X is pair produced from a resonance. We consider separate scenarios, with different initial constraints on the invisible particle momenta, and present a systematic method to identify the kinematically allowed mass regions in the ( m N , m X ) plane. These allowed regions exhibit a cusp structure at the true mass point, which is equivalent to the one observed in the m T 2 endpoints in certain cases. By considering the boundary of the allowed mass region we systematically define kinematical variables which can be used in measuring the unknown masses, and find a new expression for the m T 2 variable as well as its inverse. We explicitly apply our method to the case that X is pair produced from a resonance, and as a case study, we consider the process pp → A → χ ˜ 1 + χ ˜ 1 − $${\tilde{\chi}}_1^{+}{\tilde{\chi}}_1^{-}$$ , followed by χ ˜ 1 ± → ℓ ± ν ˜ ℓ $${\tilde{\chi}}_1^{\pm}\to {\ell}^{\pm}\;{\tilde{\nu}}_{\ell }$$ , in the Minimal Supersymmetric Standard Model and show that our method provides a precise measurement of the chargino and sneutrino masses, m X and m N , at 14 TeV LHC with 300 fb −1 luminosity