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Register a new userElectroweak top-quark pair production at the LHC with $Z$ bosons to NLO QCD in POWHEG
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We present the calculation of the NLO QCD corrections to the electroweak production of top-antitop pairs at the CERN LHC in the presence of a new neutral gauge boson. The corrections are implemented in the parton shower Monte Carlo program POWHEG. Standard Model (SM) and new physics interference effects are properly taken into account. QED singularities, first appearing at this order, are consistently subtracted. Numerical results are presented for SM and $Z$ total cross sections and distributions in invariant mass, transverse momentum, azimuthal angle and rapidity of the top-quark pair. The remaining theoretical uncertainty from scale and PDF variations is estimated, and the potential of the charge asymmetry to distinguish between new physics models is investigated for the Sequential SM and a leptophobic topcolor model.
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We describe predictions for top-quark pair differential distributions at hadron colliders, which combine state-of-the-art NNLO QCD calculations and NLO electroweak corrections together with double resummation at NNLL$$ accuracy of threshold logarithms and small-mass logarithms. This is the first time that such a combination has appeared in the literature. Numerical results are presented for the invariant-mass distribution, the transverse-momentum distribution as well as rapidity distributions.
We extend and improve upon our previous calculation of electroweak top-quark pair hadroproduction in extensions of the Standard Model with extra heavy neutral and charged spin-1 resonances. In particular, we allow for flavour-non-diagonal $Z$ couplings and take into account non-resonant production in the SM and beyond including the contributions with $t$-channel $W$ and $W$ bosons. All amplitudes are generated using the Recola2 package. As in our previous work, we include NLO QCD corrections and consistently match to parton showers with the POWHEG method fully taking into account the interference effects between SM and new physics amplitudes. We consider the Sequential Standard Model, the Topcolour model, as well as the Third Family Hypercharge Model featuring non-flavour-diagonal $Z$ couplings which has been proposed recently to explain the anomalies in $B$ decays. We present numerical results for $t bar t$ cross sections at hadron colliders with a centre-of-mass energy up to 100 TeV.
The precision measurement of the mass of the $W$ boson is an important goal of the Fermilab Tevatron and the CERN Large Hadron Collider (LHC). It requires accurate theoretical calculations which incorporate both higher-order QCD and electroweak corrections, and also provide an interface to parton-shower Monte Carlo programs which make it possible to realistically simulate experimental data. In this paper, we present a combination of the full ${cal O}(alpha)$ electroweak corrections of {tt WGRAD2}, and the next-to-leading order QCD radiative corrections to $Wtoell u$ production in hadronic collisions in a single event generator based on the {tt POWHEG} framework, which is able to interface with the parton-shower Monte Carlo programs {tt Pythia} and {tt Herwig}. Using this new combined QCD+EW Monte Carlo program for $W$ production we provide numerical results for total cross sections and kinematic distributions of relevance to the $W$ mass measurement at the Tevatron and the LHC for the processes $pp,pbar p to W^pm to mu^pm u_mu$. In particular, we discuss the impact of EW corrections in the presence of QCD effects when including detector resolution effects.
In this work, we investigate the prompt $J/psi$ production in associated with top quark pair to leading order in the nonrelativistic QCD factorization formalism at the LHC with $sqrt{s} =13$ TeV. In addition to the contribution from direct $J/psi$ production, we also include the indirect contribution from the directly produced heavier charmmonia $chi_{cJ}$ and $psi^prime$. We present the numerical results for the total and differential cross sections and find that the $sideset{^3}{^{(8)}_1}{mathop{{S}}}$ states give the dominant contributions. The prompt $tbar t J/psi$ signatures at the LHC are analyzed in the tetralepton channel $ppto (tto W^+(ell^+ u)b) (bar t to W^-(ell^- bar u)bar b) (J/psitomu^+mu^-)$ and trilepton channel $ppto (tto W(q q^prime)b) ( t to W(ell u) b) (J/psitomu^+mu^-)$, with the $J/psi$ mesons decaying into muon pair, and the top quarks decaying leptonically or hadronically. We find that $tbar t J/psi$ proudction can be potentially detected at the LHC, whose measurement is useful to test the heavy quarkonium production mechanism.
We present results for the next-to-leading order QCD corrections to the production and semi-leptonic decays of a top quark pair in hadron collisions, retaining all spin correlations. To evaluate the virtual corrections, we employ generalized D-dimensional unitarity. The computation is implemented in a numerical program which allows detailed studies of ttbar-related observables at the Tevatron and the LHC.
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