Related papers: Probing New Physics using top quark polarization i…
We calculate the electroweak corrections of the order $O({m_t^2\over v^2})$ to the QCD production of $t\bar{t}$ pairs via $q+qbar->t+tbar$ at hadron colliders and show that these corrections to the total production rate are small. This…
We discuss four-fermion contact-interaction searches in the processes e^+e^-\to\mu^+\mu^-, c{\bar c} and b{\bar b} at a future e^+e^- Linear Collider with c.m. energy \sqrt{s}=0.5 TeV and with both beams longitudinally polarized. Our…
We parameterize the non-universal couplings of t-t-Z and t-b-W in the electroweak chiral lagrangian approach, and examine the constraints on these parameters from the LEP data. We also study how the SLC, Tevatron, LHC and NLC can improve…
Based on a model-independent framework including the vector-like top partner (VLQ-$T$), we investigate the prospect of discovering the singlet or doublet VLQ-$T$ via the single production process $e^{-}e^{+}\to T\bar{t}+t\bar{T}$ with the…
We present a study of top quark polarization in $t \overline{t}$ events produced in $p \overline{p}$ collisions at $\sqrt{s}=1.96$ TeV. Data correspond to 9.7 fb$^{-1}$ collected with the D0 detector at the Tevatron. We use final states…
We studied the sensitivity of the process $e^+e^-\to \ell \nu q\bar{q}'$ to anomalous trilinear gauge boson couplings of the $WW\gamma$ and WWZ vertices at the center of mass energies $\sqrt{s}=500$ GeV and 1 TeV. The bounds for the…
In the framework of topcolor-assisted technicolor model we calculate the contributions from the pseudo Goldstone bosons and new gauge bosons to $e^+e^- \to t\bar{t}$. We find that, for reasonable ranges of the parameters, the pseudo…
The sensitivity of optimal integrated observables to electroweak triple gauge couplings is investigated for the process e-e+ -> W-W+ -> 4 fermions at future linear colliders. By a suitable reparameterisation of the couplings we achieve that…
We study the potential of a future $e^+e^-$ collider for the search of anomalous gamma t t bar and Z t t bar couplings, assuming that CP-invariance holds. This is done in a model-independent way, considering that all six possible couplings…
We show how to determine the electric and weak dipole moments of the top quark simultaneously and independently from $e^+e^-\to t\bar t$ at $\sqrt{s}=500$ GeV NLC. To obtain the best accuracies with which the dipole moments can be measured,…
We describe a detailed study of the process $e^+e^- \to \ell\nu_\ell q \bar{q}$ and the measurement of tri-linear gauge boson couplings (TGV's) at LEP200 and at a 500~GeV and 1~TeV NLC. We included all tree level Feynman diagrams…
This thesis presents a study of the prospects of measuring electroweak production of the top quark at the LHC. The study of the top quark is a highly topical subject as we expect significant numbers of top quarks at the LHC which will…
We study the nature of the flavor changing neutral couplings of the top quark with the Higgs boson and the up/charm quark in the $t\bar{t}$ production at linear colliders. There are previous bounds on such tqH couplings at both, linear and…
We investigate the possibility of detecting a scalar leptoquark, coupling to the electron and the top, at a linear collider. For coupling strength equalling the weak coupling constant, the present mass bounds are of the order of 300 GeV. We…
We calculate the linear polarization of gluons radiated off top quarks produced in e^+e^- annihilations. For typical top pair production energies at the Next-Linear-Collider (NLC) the degree of linear polarization remains close to its soft…
The production of W+ W- b bbar from e+ e- collisions at energies close to the t tbar threshold is dominated by the resonant process with a nearly on-shell t tbar intermediate state. The W b pairs in the final state can also be reached…
We provide a comprehensive analysis of the power of including top quark-polarisation information to kinematically challenging $t\bar t$ resonance searches, for which ATLAS and CMS start losing sensitivity. Following the general modeling and…
The rate and corresponding gluon jet energy distribution for the process $e^+e^- \to t\bar tg$ are sensitive to the presence of anomalous dipole-like couplings of the top to the photon and $Z$ at the production vertex as well as to the…
Fermion compositness, and other new physics which can be described by an exchange of very massive particles ($Z^\prime$ boson, leptoquarks, sparticles with R-parity violating couplings), can be manifest itself as the presence of a strong…
For contact-interaction searches at the Linear Collider, we discuss the advantages of polarizing both the electron and the positron beams as compared with polarizing only the electron beam. In particular, for the processes e^+e^-\to…