Related papers: Simple models for the top asymmetry: constraints a…
New gauge bosons with Standard Model-like couplings to leptons are constrained by collider searches to be heavier than approximately ~1 TeV. A Z' boson with suppressed couplings to leptons, however, could be much lighter and possess…
We present a phenomenological analysis of the recent Tevatron results on the $t \bar t$ forward-backward asymmetry and invariant-mass spectrum assuming a new contribution from an s-channel gluon resonance with a mass in the range from 700…
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…
We derive generic predictions at hadron colliders from the large forward-backward asymmetry observed at the Tevatron, assuming the latter arises from heavy new physics beyond the Standard Model. We use an effective field theory approach to…
The anomaly of the top quark forward-backward asymmetry $A^t_{FB}$ observed at the Tevatron can be explained by the t-channel exchange of a neutral gauge boson (Z') which has sizable flavor changing coupling for top and up quarks. This…
The discovery potential and diagnostic abilities of proposed future colliders for new heavy neutral ($Z'$) and charged ($W'$) gauge bosons are summarized. Typical bounds achievable on $M_{Z',W'}$ at the TEVATRON, DI-TEVATRON, LHC, 500 GeV…
We consider a class of minimal extensions of the Standard Model with an extra massive neutral gauge boson Z'. They include both family-universal models, where the extra U(1) is associated with (B-L), and non-universal models where the Z' is…
We reanalyse the potential of the LHC to discover new $Z'$ gauge bosons and to discriminate between various theoretical models. Using a fast LHC detector simulation, we have investigated how well the characteristics of $Z'$ bosons from…
Extensions of the Standard Model often predict new chiral interactions for top quark, which will contribute to top quark spin correlation and polarization in $t\bar{t}$ production at the LHC. In this work, under the constraints from the…
A sizable charge asymmetry in top quark pair production has been observed at the Tevatron. The experimental results seem to exceed systematically the Standard Model theory predictions by a significant amount and have triggered a large…
The top quark forward-backward asymmetry measured at the Tevatron collider shows a large deviation from standard model expectations. Among possible interpretations, a non-universal $Z^\prime$ model is of particular interest as it naturally…
Predictions are made for the forward-backward and charge asymmetries in bottom-quark pair production at hadron colliders. Tree-level exchanges of electroweak (EW) gauge bosons dominate the Standard Model (SM) contribution to the asymmetry…
The contributions of $G'$-boson predicted by the chiral color symmetry of quarks to the charge asymmetry $A_C(p p \to t\bar{t})$ in $t \bar{t}$ production at the LHC and to the forward-backward asymmetry $A_{\rm FB}(p\bar{p} \to t\bar{t})$…
The experimental results on the t bar t production cross section at the Tevatron are well described by the QCD contributions within the standard model, while the recent measurement of the forward-backward asymmetry cannot be accounted for…
We review the status of heavy neutral gauge bosons, Z', with emphasis on constraints that arise in supersymmetric models, especially those motivated from superstring compactifications. We first summarize the current phenomenological…
We propose an efficient method to explore models which which produce like-sign tops at the LHC, using the total charge asymmetry of single lepton events instead of like-sign dileptons. As an example, the method is implemented on a Z' Model,…
We consider new physics contributions to the top-quark forward-backward asymmetry from a neutral $V^0_8$ or charged $V^+_8$ color-octet vector exchanged in the $t$-channel. We study the phenomenological constraints on these particles…
We propose that, within the standard model, the correlation between the $t\bar{t}$ forward--backward asymmetry $A_{t\bar t}$ and the corresponding lepton-based asymmetry $A_l$ -- at the differential level -- is strong and rather clean both…
Measurements of the top quark forward-backward asymmetry performed at the Tevatron suggest that new-physics may be playing a role in t-tbar production. To better understand the source of the asymmetry, recent proposals have called for a…
By exploiting the correlation between charge and spin polarisation asymmetries in t-tbar, we show that combining the two observables could identify the presence of quasi-degenerate states in a resonant signal at the LHC. As an example, we…