Related papers: Top flavour-changing neutral coupling signals at a…
We study the rare top-quark decay t->ch, where h is a generic Higgs boson, at a linear collider. If kinematically accessible, all models contain this decay at some level due to quark flavor mixing. Some models, such as Model III of the…
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…
The $h(125)$ boson, discovered only in 2012, is lower than the top quark in mass, hence $t \to ch$ search commenced immediately thereafter, with current limits at the per mille level and improving. As the $t \to ch$ rate vanishes with the…
The perspectives for the observation of the rare decay H -> mumu decay and the determination of the muon Yukawa coupling at a TeV-class and at a multi-TeV e+e- linear colliders are discussed. The signal for the decay can be obtained at 0.8…
In absence of the Standard Model Higgs boson the interaction among the gauge bosons becomes strong at high energies and influences the couplings between them. Each trilinear and quartic gauge boson vertex is characterised by a set of…
The observation of lepton flavor violation indicates new physics beyond the Standard Model. Lepton colliders are ideal facilities to probe charged lepton flavor violation (CLFV) signals induced by new physics at high energy. In this work we…
We discuss the polarization of top quarks produced at a polarized linear e^+ e^- collider. Close-to-maximal values of the top quark polarization can be achieved with longitudinal beam polarizations (h_- = -0.80, h_+ = +0.625) or (h_- =…
The capability of the NLC run in the $\gamma e$ collision mode to probe the CP-conserving $\gamma WW$ and $\gamma ZZ$ anomalous couplings through the use of the polarization asymmetry is reviewed. When combined with other measurements, very…
This article presents a search for flavour-changing neutral currents in the decay of a top quark into an up-type ($q = c, u$) quark and a Higgs boson, where the Higgs boson decays into two photons. The proton--proton collision data set…
We examine very general four-point interactions arising from new physics and contributing to the Higgs production process e+e- -> HZ. We write all possible forms for these interactions consistent with Lorentz invariance. We allow the…
We propose a new method for detecting a charged (pseudo-)scalar at colliders, based upon the observation that its Yukawa coupling to charm and bottom quarks can be large due to a significant mixing of the top and charm quarks. After…
Heavy neutrinos at the TeV scale have been searched for at the LHC in the context of left-right models, under the assumption that they couple to the electron, the muon, or both. We show that current searches are also sensitive to heavy…
If the LHC should fail to observe direct signals for new physics, it may become necessary to look for new physics effects in rare events such as flavour-changing decays of the top quark, which, in the Standard Model, are predicted to be too…
A weakly coupled new neutral gauge boson forms a narrow resonance that is hard to discover directly in e+e- collisions. However, if the gauge boson mass is below the center-of-mass energy, it can be produced through processes where the…
During the LEP2 period the e+e- collider increased its center of mass energy from 161 GeV to 209 GeV and a total integrated luminosity of approximately 700 pb-1 was recorded per experiment. Pairs of W bosons are produced and allow the study…
The introduction of a longitudinal polarised positron beam in an $e^+e^-$ linear collider calls for its polarisation monitoring and measurement at low energies near its production location. Here it is shown that a relatively simple Bhabha…
We study the sensitivity of $ e \gamma$ colliders to physics beyond the Standard Model, when such interactions are natural and their scale lies below the collider energy. Using the reaction $ e \gamma \to b t \nu$ as a specific example, we…
We study the sensitivity of top pair production with six-fermion decay at the LHC to the presence and nature of an underlying Z' boson, accounting for full tree-level Standard Model ttbar interference, with all intermediate particles…
Understanding the mechanism of electroweak symmetry breaking and the origin of boson and fermion masses is among the most pressing questions raised in contemporary particle physics. If these issues involve one (several) Higgs boson(s), a…
In this study, assuming the type-I 2HDM at SM-like scenario, observability of heavy neutral CP-even and CP-odd Higgs bosons $H$ and $A$ at a linear collider operating at $\sqrt{s}=1$ TeV is investigated through the signal process chain $e^-…