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Ning Liu

Publications and source records attributed to Ning Liu.

254 records · Page 15Linked to original sources

Probing topcolor-assisted technicolor from top charge asymmetry and triple-top production at the LHC

In a topcolor-assisted technicolor model (TC2) with large FCNC top quark couplings, we study its correlated contributions to the top quark forward-backward asymmetry ($A_{FB}$) at the Tevatron, the top charge asymmetry ($A_{C}$) and the triple-top production at the LHC. Under current constraints on the top quark from the LHC and Tevatron(such as the total and differential production rates), we scan the parameter space of such a TC2 model. We find that in the allowed parameter space the TC2 model can explain the Tevatron measured $A_{FB}$ at $2σ$ level, but meanwhile significantly enhance $A_{C}$ at the LHC. Such enhanced $A_{C}$, albeit currently allowed by the LHC measurement at $2σ$ level, will serve as a test of TC2 with the improvement of measurement precision at the LHC. Then with all the constraints (including the requirement to explain $A_{FB}$ at $2σ$ level and satisfying the current LHC measurement of $A_{C}$ at $2σ$ level), we find that the TC2 model can induce sizable triple-top production at the 14 TeV LHC (the production rate can maximally reach 16 pb). Due to the low SM backgrounds, the triple-top production can also be a good probe for TC2 model, complementary to $A_{C}$.

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QCD corrections to the production of $t\bar{t}γ$ at the ILC

A precise calculation of the top quark pair production associated with a hard photon is essential for testing the electroweak property of the top quark in the Standard Model (SM). We investigate the one-loop QCD corrections to the process $e^{+}e^{-} \to t\bar{t}γ$ at the International Linear Collider (ILC), and find that the $K$-factor can be as large as 1.238 (1.105, 1.060) for a center-of-mass energy $\sqrt{s}=500 (800, 1500)$ GeV. The transverse momentum distributions of the top quark and photon are respectively shown at leading order (LO) and next-to-leading order(NLO). Due to the asymmetric rapidity distribution of the top (anti-top) quark, we also study the top quark forward-backward asymmetry ($A^{t}_{FB}$) in $t\bar{t}γ$ production at NLO, which is found to be 45.82 (55.25, 55.89)% for $\sqrt{s}=500 (800, 1500)$ GeV.

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