Study of top quark dipole interactions in ttˉt\bar{t} production associated with two heavy gauge bosons at the LHC

In this paper, we investigate the prospects of measuring the strong and weak dipole moments of the top quark at the Large Hadron Collider (LHC). Measurements of these couplings provide an excellent opportunity to probe new physics interactions as they have quite small magnitudes in the Standard Model. Our analyses are through studying the production cross sections of $t\bar{t}WW$ and $t\bar{t}ZZ$ processes in the same sign dilepton and four-lepton final states, respectively. The sensitivities to strong and weak top quark dipole interactions at the $95\%$ confidence level for various integrated luminosity scenarios are derived and compared with other studies. In addition to using the total cross sections, a novel handle based on an angular observable is introduced which is found to be sensitive to variations of the top quark strong dipole moments. We also investigate the sensitivity of the invariant mass of the system to the strong and weak dipole moments of the top quark.Comment: 21 pages, 6 figures and 6 table

Single top quark production as a probe of anomalous tqγtq\gamma and tqZtqZ couplings at the FCC-ee

In this paper, a detailed study to probe the top quark Flavour-Changing Neutral Currents (FCNC) $tq\gamma$ and $tqZ$ at the future $e^{-}e^{+}$ collider FCC-ee in three different center-of-mass energies of 240, 350 and 500 GeV is presented. A set of useful variables are proposed and used in a multivariate technique to separate signal $e^- e^+ \rightarrow Z/\gamma \rightarrow t \bar{q} ~ ( \bar{t} q )$ from standard model background processes. The study includes a fast detector simulation based on the {\sc delphes} package to consider the detector effects. The $3 \sigma$ discovery regions and the upper limits on the FCNC branching ratios at 95\% confidence level (CL) in terms of the integrated luminosity are presented. It is shown that with 300 fb$^{-1}$ of integrated luminosity of data, FCC-ee would be able to exclude the effective coupling strengths above ${\cal O} (10^{-4}-10^{-5})$ which is corresponding to branching fraction of ${\cal O}(0.01-0.001)$\%. We show that moving to a high-luminosity regime leads to a significant improvement on the upper bounds on the top quark FCNC couplings to a photon or a $Z$ boson.Comment: 21 Pages, 6 Figures, 8 Table

From Tevatron's top and lepton-based asymmetries to the LHC

We define a lepton-based asymmetry in semi-leptonic ttbar production at the LHC. We show that the ratio of this lepton-based asymmetry and the ttbar charge asymmetry, measured as a function of the lepton transverse momentum or the ttbar invariant mass is a robust observable in the Standard Model. It is stable against higher order corrections and mis-modeling effects. We show that this ratio can also be a powerful discriminant among different new physics models and between them and the Standard Model. Finally, we show that a related ratio defined at the Tevatron is also robust as a function of the ttbar invariant mass.Comment: 20 page

Light Non-Abelian Vector Dark Matter Produced Through Vector Misalignment

In this paper, we examine the evolution of light, feebly interacting non-abelian dark gauge bosons dark matter in the early universe. In the region of the parameter space where the dark gauge coupling is too small for the gauge bosons to be produced efficiently via the freeze-in mechanism, the observed relic density of dark matter can be obtained via the vector misalignment mechanism. Vector misalignment has already been discussed in the case of dark photon dark matter. In this study, we extend the arguments to non-abelian gauge bosons. We specifically work on a dark sector scenario with a $SU(2)_R$ gauge symmetry, spontaneously broken by a scalar $\phi$. For sufficiently light $\lesssim O( MeV)$ and feebly interacting $g_R \lesssim 10^{-10}$ gauge boson, $W_R$ become the dark matter candidates. The portal between the dark sector and the Standard Model (SM) sector, in this study, is provided by the right-handed electron charged under $SU(2)_R$. After discussing the evolution of $W_R$ in the early universe, we study the constraints on the model and show the allowed region of the parameter space. Furthermore, the benchmark that can explain the XENON1T excess is demonstrated.Comment: 16 pages, 5 figure

Top Quark Asymmetries and Unparticle Physics

Among different measured observables of top-antitop quark pairs at hadron colliders, the forward-backward asymmetry ($A_{\text{FB}}$) measured by the CDF and D0 collaborations has inconsistency with the Standard Model prediction. The measured forward-backward asymmetry grows with $t\bar{t}$ invariant mass. Several new physics models have been proposed to explain this deviation. We consider the consistency of the parameter space of vector unparticle (in Flavor-Conserving scenario) with the existing $t\bar{t}$ production measurements. In particular, we look at the total cross sections at the LHC and Tevatron, differential cross section with $t\bar{t}$ invariant mass, and the LHC charge asymmetry to identify the regions in parameter space that can give the desired top $A_{\text{FB}}$ observed by the Tevatron. We show that in spite of the intrinsic tension between the LHC charge asymmetry and $A_{\text{FB}}$, there exists a region in the unparticle parameters space where the top $A_{\text{FB}}$ and the LHC charge asymmetry are satisfied simultaneously. Finally, we show that the consistent region with $t\bar{t}$ observables is consistent with the constraints coming from the dijet resonance searches.Comment: 12 pages,5 figure