Related papers: Longitudinal top polarisation measurement and anom…
We survey the expected polarization of the top produced in the decay of a scalar top quark, $\tilde t \rightarrow {\tilde t}\chi_i^0, i =1-2$. The phenomenology is quite interesting, since the expected polarization depends both on the…
We discuss top quark production and its subsequent decay for searching new physics at lepton colliders. The angular dependence of the decay leptons is calculated including both QCD corrections and anomalous gamma Z - t tbar couplings. The…
We review recent measurements of the properties of the top quark: the decay width of the top quark, of spin correlations between the top and the antitop quarks in $\ttbar$ production, the $W$ boson helicity in top decays, the strong colour…
We propose to measure the threshold lepton asymmetry, that is the forward-backward asymmetry of the charged lepton in ttbar events near the production threshold. At threshold top quark pairs are produced in an s-wave. Angular momentum…
We present new direct constraints on a general $Wtb$ interaction using data corresponding to an integrated luminosity of 5.4 fb$^{-1}$ collected by the D0 detector at the Tevatron $p\bar{p}$ collider. The standard model provides a purely…
The production cross--section and distributions of the top quark are sensitive to new physics, e.g., the $t\overline{t}$ system can be a probe of new resonances or gauge bosons that are strongly coupled to the top quark, in analogy to…
We present a calculation of the single top quark cross section for proton-antiproton interactions with sqrt(s) = 1.8 TeV at the Fermilab Tevatron collider. We examine the effects of top mass, parton distribution functions, QCD scale, and…
In the standard model, for the t --> W b decay mode, the relative phase is 0-degrees between the dominant A(0,-1/2) and A(-1, -1/2) helicity amplitudes. However, in the case of an additional large t_R --> b_L chiral weak-transition moment,…
The rates and corresponding jet distributions for the decay $Z\to b\bar bg$ and the process $e^+e^-\to t\bar tg$ may be sensitive to anomalous dipole-like couplings of heavy quarks to the photon and $Z$. In the $b$-quark case, after…
We discuss top quark production and its subsequent decay at lepton colliders including both QCD corrections and anomalous gamma / Z - t t-bar couplings. The off-diagonal spin basis for the top and anti-top quarks is shown to be useful to…
We present a study of the experimental determination of the forward-backward asymmetry in the process $e^+e^-\to t\bar t$ and in the subsequent $t\to Wb$ decay, studied in the context of the International Linear Collider. This process…
Motivated by the need to set bounds on the third generation charged couplings, we study the mechanism of single top production at the LHC, analyzing the sensitivity of different observables to the magnitude of the effective left and right…
Forward-backward asymmetries $A_{FB}^t$ and $A_{FB}^\ell$ are observed in the top quark $t$ rapidity distribution and in the rapidity distribution of charged leptons $\ell$ from top quark decay at the Tevatron proton-antiproton collider,…
We calculate the ${\cal O}(\alpha_s)$ radiative corrections to the spin dependent differential decay rates of the process $t\rightarrow b+W^+$. These are needed to study the angular distribution of the energy of hadrons produced in…
Recent experimental results from the CDF collaboration which study the top forward-backward asymmetry have strengthened the case that new physics is playing a role in t-tbar production. Here we propose a set of measurements, built from the…
We consider how the measurement of top polarization at the Tevatron can be used to characterise and discriminate among different new physics models that have been suggested to explain the anomalous top forward-backward asymmetry reported at…
New physics interactions can affect the strength and structure of the $tbW$ vertex. We investigate the magnitudes and phases of "anomalous" contributions to this vertex in a two-Higgs doublet and the minimal supersymmetric extension of the…
We examine the contributions of various couplings in general ZZH and gammaZH interactions arising from new physics to the Higgs production process e+e- --> HZ, followed by the decay of the Z into a charged-lepton pair. We take into account…
We study in a model-independent way anomalous CP-violating tbW effective couplings that might arise from new physics in the processes pp-> tW^- X and pp-> tbar W^+X, followed by semileptonic decay of t and tbar. These processes have a…
The charged Higgs boson is quite common in many new physics models. In this study we examine the potential of observing a heavy charged Higgs boson in its decay mode of top-quark and bottom-quark in the Type-II Two-Higgs-Doublet-Model. In…