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Register a new userElectroweak corrections to $ggto H^{-}tbar{b}$ at the LHC
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The dominant contribution to $H^- tbar{b}$ production at the LHC is the gluon-gluon fusion parton subprocess. We perform for the case of the complex MSSM a complete calculation of the NLO electroweak contributions to this channel. The other small contributions with quarks or photon in the initial state are calculated at tree level. The results are improved by using the effective bottom-Higgs couplings to resum the leading radiative corrections. We find that, beyond these leading corrections, the NLO electroweak contributions can be still be significant. The effect of the complex phases of the soft-breaking parameters is found to be sizable.
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We report on our recent work on electroweak corrections to $tbar{t}$ production at hadron colliders. Specifically, we discuss the weak-interaction contributions to the top quark transverse momentum and $t bar{t}$ invariant mass distributions and an induced parity-violating top-spin asymmetry.
We present a state-of-the-art calculation of the next-to-leading-order electroweak corrections to ZZ production, including the leptonic decays of the Z bosons into $mu^+mu^-mathrm{e}^+mathrm{e}^-$ or $mu^+mu^-mu^+mu^-$ final states. We use complete leading-order and next-to-leading-order matrix elements for four-lepton production, including contributions of virtual photons and all off-shell effects of Z bosons, where the finite Z-boson width is taken into account using the complex-mass scheme. The matrix elements are implemented into Monte Carlo programs allowing for the evaluation of arbitrary differential distributions. We present integrated and differential cross sections for the LHC at 13 TeV both for an inclusive setup where only lepton identification cuts are applied, and for a setup motivated by Higgs-boson analyses in the four-lepton decay channel. The electroweak corrections are divided into photonic and purely weak contributions. The former show the well-known pronounced tails near kinematical thresholds and resonances; the latter are generically at the level of $sim-5%$ and reach several $-10%$ in the high-energy tails of distributions. Comparing the results for $mu^+mu^-mathrm{e}^+mathrm{e}^-$ and $mu^+mu^-mu^+mu^-$ final states, we find significant differences mainly in distributions that are sensitive to the $mu^+mu^-$ pairing in the $mu^+mu^-mu^+mu^-$ final state. Differences between $mu^+mu^-mathrm{e}^+mathrm{e}^-$ and $mu^+mu^-mu^+mu^-$ channels due to interferences of equal-flavour leptons in the final state can reach up to $10%$ in off-shell-sensitive regions. Contributions induced by incoming photons, i.e. photon-photon and quark-photon channels, are included, but turn out to be phenomenologically unimportant.
The production of a neutral and a charged vector boson with subsequent decays into three charged leptons and a neutrino is a very important process for precision tests of the Standard Model of elementary particles and in searches for anomalous triple-gauge-boson couplings. In this article, the first computation of next-to-leading-order electroweak corrections to the production of the four-lepton final states $mu^+mu^- e^+ u_e$, $mu^+mu^- e^- bar u_e$, $mu^+mu^- mu^+ u_mu$, and $mu^+mu^- mu^- bar u_mu$ at the Large Hadron Collider is presented. We use the complete matrix elements at leading and next-to-leading order, including all off-shell effects of intermediate massive vector bosons and virtual photons. The relative electroweak corrections to the fiducial cross sections from quark-induced partonic processes vary between $-3%$ and $-6%$, depending significantly on the event selection. At the level of differential distributions, we observe large negative corrections of up to $-30%$ in the high-energy tails of distributions originating from electroweak Sudakov logarithms. Photon-induced contributions at next-to-leading order raise the leading-order fiducial cross section by $+2%$. Interference effects in final states with equal-flavour leptons are at the permille level for the fiducial cross section, but can lead to sizeable effects in off-shell sensitive phase-space regions.
The production of WWZ at the LHC is an important process to test the quartic gauge couplings of the Standard Model as well as an important background for new physics searches. A good theoretical understanding at next-to-leading order (NLO) is therefore valuable. In this paper, we present the calculation of the NLO electroweak (EW) correction to this channel with on-shell gauge bosons in the final state. It is then combined with the NLO QCD correction to get the most up-to-date prediction. We study the impact of these corrections on the total cross section and some distributions. The NLO EW correction is small for the total cross section but becomes important in the high energy regime for the gauge boson transverse momentum distributions.
A feasibility study for an experimental analysis searching for $tbar{t}H(Hrightarrow bbar{b})$ production at the LHC and its high luminosity phase is presented in this note. Unlike search strategies currently being used in experimental collaborations, the present analysis exploits jet substructure techniques and focuses on the reconstruction of boosted Higgs bosons, to obtain sensitivity to the signal in a simple cut-based analysis. The $tbar{t} +$ jets background may be constrained in the proposed analysis through a control region with very small signal contamination. Using this analysis strategy, the $tbar{t}H(Hrightarrow bbar{b})$ process could be observed at the LHC, in the semi-leptonic channel alone, with a significance of $5.41pm 0.12$ for $mathcal{L}=300,mbox{fb}^{-1}$. For the same integrated luminosity, in the High Luminosity LHC scenario with an upgraded detector, a significance of $6.13pm 0.11$ may be obtained. The top Yukawa coupling could be measured with a 35% uncertainty using $mathcal{L}=300,mbox{fb}^{-1}$ of LHC data and of 17% at the HL-LHC scenario with $mathcal{L}=3000,mbox{fb}^{-1}$. In the same luminosity scenarios, the signal strength is equally expected to have a 18$%$ and 5$%$ uncertainty, respectively. Finally, it was found that re-clustered jets may be used without loss of efficiency.
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