Related papers: Four-Fermi Effective Operators at e^+ e^- ---> \ba…
Both collider searches and direct detections are promising approaches to probe fermionic dark matter. In this paper, we study signatures of four-fermion contact operators involving a dark fermion, an electron, and a quark pair. We show that…
Four top quark production is a rare standard model process that has been observed for the first time in proton-proton collisions at \sqrts at the CERN LHC by both the ATLAS and CMS Collaborations. Both observations were made in the…
The threshold behaviour of the cross section sigma(e+e- -> tau+tau-) is analysed, taking into account the known higher-order corrections. At present, this observable can be determined to next-to-next-to-leading order (NNLO) in a combined…
If neutrinos are Dirac particles and, as suggested by the so far null LHC results, any new physics lies at energies well above the electroweak scale, the Standard Model effective field theory has to be extended with operators involving the…
We complete the one loop renormalization of the HQET lagrangian at O(1/m_Q^3) including four fermion operators with two heavy and two light quark fields in the operator basis. It is shown that as a consequence the short distance…
The process of top-quark pair production at future high-energy $e^+ e^-$ linear colliders has been investigated as a possible test of physics beyond the Standard Model. Non-standard interactions have been assumed both for the production and…
We investigate the sensitivity of top pair production to the properties of different Beyond the Standard Model theories embedding a new neutral boson. We include six-fermion decay, and account for the full tree-level Standard Model ttbar…
We consider excited lepton ($\bar{l^*}l {\rm or} \bar{l^*}l^*$) production in the context of effective theories with being four-fermion contact interaction at LHC. We also consider the two body decay mode of excited lepton ($l^*$) to…
At hadron colliders, top quarks are dominantly produced in pairs ($t\bar{t}$), a production mechanism that was discovered more than twenty years ago at the Tevatron in Fermilab. Although the \ttbar process has already entered the domain of…
In this article we consider the Standard Model extended by a number of (light) right-handed neutrinos, and assume the presence of some heavy physics that cannot be directly produced, but can be probed by its low-energy effective…
If neutrinos are Dirac particles the existence of light right-handed neutrinos $\nu_{R}$ is implied. Those would contribute to the effective number of relativistic neutrino species $N_{{\rm eff}}$ in the early Universe. With pure standard…
Motivated by the possibility that the right-handed top-quark (t_R) is composite, we discuss the effects of dimension-six operators on the Higgs boson production at the LHC. When t_R is the only composite particle among the Standard Model…
We discuss ways to explore non-standard interactions (NSI) which neutrinos may possess by expressing them as effective four Fermi operators with coefficient of the order of (M_{W} / M_{NP})^2 ~0.01 (0.0001) for energy scales of new physics…
Non-standard scenarios described by effective contactlike interactions can be revealed only by searching for deviations of the measured observables from the Standard Model (SM) predictions. If deviations were indeed observed within the…
We discuss the production, at high--energy e$^+$e$^-$ linear colliders, of new heavy fermions predicted by extensions of the Standard Model. We analyze in great details the various signals and the corresponding backgrounds for both pair…
We consider an extension of the Standard Model with two right-handed singlet fermions with mass at the electroweak scale that induce neutrino masses, plus a generic new physics sector at a higher scale $\Lambda$. We focus on the effective…
We study an extension of the Standard Model with electroweak scale right-handed singlet fermions $N$ that induces neutrino masses, plus a generic new physics sector at a higher scale $\Lambda$. The latter is parametrized in terms of…
Precision predictions for phenomenologically interesting observables such as the t-tbar invariant mass distribution and forward-backward asymmetry in top-quark pair production at hadron colliders require control over the differential cross…
In an effective theory approach, the full minimal set of leading contributions to anomalous charged-current top couplings comprises various new trilinear tbW as well as quartic tbff' interaction vertices, some of which are related to one…
We present predictions for the total top-quark pair production cross section at the Tevatron and the LHC with 7,8 and 14 TeV centre-of-mass energy, including the resummation of threshold logarithms and Coulomb corrections through…