Next-to-leading order QCD effect of $W'$ on top quark Forward-Backward Asymmetry

Physical review D: Particles and fields 10/2011; DOI: 10.1103/PhysRevD.85.034020
Source: arXiv

ABSTRACT We present the calculations of the complete next-to-leading order (NLO) QCD
corrections to the total cross section, invariant mass distribution and the
forward-backward asymmetry ($\rm A_{FB}$) of top quark pair production mediated
by $W'$ boson. Our results show that in the best fit point in the parameter
space allowed by data at the Tevatron, the NLO corrections change the new
physics contributions to the total cross section slightly, but increase the
$\rm A_{FB}$ in the large invariant mass region by about 9%. Moreover, we
evaluate the total cross section and charge asymmetry ($\rm{A}_{\rm{C}}$) of
top pair production at the LHC, and find that both total cross section and
$A_{\rm C}$ can be used to distinguish NP from SM with the integrated
luminosity increasing.

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    ABSTRACT: The excess of top quark forward-backward asymmetry ($A^t_{FB}$) reported by the Tevatron and the enhancement of the Higgs decay to diphoton observed by the LHC may point to a same origin of new physics. In this note we examined such anomalies in the two-Higgs-doublet model with a color-triplet scalar. We found that under current experimental constraints this model can simultaneously explain both anomalies at $1\sigma$ level. Also, we examined the Higgs decay $h\to Z\gamma$ and displayed its correlation with $h\to \gamma\gamma$. We found that unlike other models, this model predicts a special correlation between $h\to Z\gamma$ and $h\to \gamma\gamma$, i.e., the $Z\gamma$ rate is highly suppressed while the $\gamma\gamma$ rate is enhanced. This behavior may help to distinguish this model in the future high luminosity run of the LHC.
    European Physical Journal C 12/2012; · 5.44 Impact Factor
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    ABSTRACT: We analyze the impact of effective axial-vector coupling of the gluon on spin polarization observables in $t\bar{t}$ pair production at the LHC. Working at leading order in QCD, we compute the $t\bar{t}$ spin-correlation and left-right spin asymmetry coefficients in the helicity basis in the laboratory frame as functions of the new physics scale $\Lambda$ associated with this coupling. We found that the $t\bar{t}$ invariant mass dependent asymmetries are more sensitive to the scale $\Lambda$ than the corresponding inclusive ones, in particular when suitable cuts selecting high $t\bar{t}$ invariant mass regions are imposed. In the context of this scenario, we show that the LHC has potential either to confirm or to rule out the Tevatron FB top asymmetry anomaly by analyzing the $t\bar{t}$ spin-correlation and left-right polarization asymmetries. On the other hand, stringent lower bound on the new physics scale $\Lambda$ can be set in this scenario if no significant deviations from the SM predictions for those observables will be measured.
    Physical Review D 12/2012; 87(5). · 4.69 Impact Factor
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    ABSTRACT: We study the connection between the same sign top (SST) and the top quark forward-backward asymmetry $A^t_{FB}$. We find that a large class of new physics models that have been proposed to account for the $A^t_{FB}$ lead to SST quark production rate much larger than the observed rate at the LHC and consequently are severely constrained or ruled out. Our model independent, general, operator analysis shows that none of the tree-level flavor-changing operators are able to explain $A^t_{FB}$ and simultaneously remain consistent with the same-sign top-quark production constraints from the LHC data.
    Journal of High Energy Physics 01/2013; 2013(4). · 6.22 Impact Factor

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