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Sara Khatibi

Publications and source records attributed to Sara Khatibi.

20 records · Page 2Linked to original sources

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.

hep-ph↗

Top Quark Forward-Backward Asymmetry and $W'$-Boson with General Couplings

The measured forward-backward asymmetry in top pair events at the Fermilab Tevatron collider deviates significantly from the standard model expectation. Several models have been proposed to describe the observed asymmetry which grows with the rapidity difference of the top pairs and also with the $t\bar{t}$ invariant mass. The presence of a heavy charged gauge boson $W'$ with the coupling $W'-t-d$ (left-handed, right-handed, and a mixture of left and right-handed couplings) could generate the desired top forward-backward asymmetry keeping the top pair cross section consistent with the standard model prediction. Such $W'$-boson makes contribution to the electric dipole moment of the neutron through contribution to the $d$-quark electric dipole moment, recently measured charge asymmetry ($A_{C}$) by the LHC experiments, and the total cross section of top pair at the LHC and Tevatron. We show that the upper bounds on neutron and top electric dipole moments disfavour any $W'$ with a mass below 240 GeV which could explain the Tevatron forward-backward asymmetry. It is shown that the charge asymmetry provides an allowed region in the parameters space with no overlap with the allowed region where the asymmetry could be described.

hep-ph↗