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Register a new user$tbar{t}H$ production at NNLO: the flavour off-diagonal channels
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We consider QCD radiative corrections to the associated production of a heavy-quark pair ($Q{bar Q}$) with a generic colourless system $F$ at hadron colliders. We discuss the resummation formalism for the production of the $Q{bar Q}F$ system at small values of its total transverse momentum $q_T$. The perturbative expansion of the resummation formula leads to the explicit ingredients that can be used to apply the $q_T$ subtraction formalism to fixed-order calculations for this class of processes. We use the $q_T$ subtraction formalism to perform a fully differential perturbative computation for the production of a top-antitop quark pair and a Higgs boson. At next-to-leading order we compare our results with those obtained with established subtraction methods and we find complete agreement. We present, for the first time, the results for the flavour off-diagonal partonic channels at the next-to-next-to-leading order.
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Precision studies of the properties of the top quark represent a cornerstone of the LHC physics program. In this contribution we focus on the production of $tbar{t}$ pairs in association with one hard jet and in particular on its connection with precision measurements of the top quark mass at the LHC. We report a summary of a full calculation of the process $pp to e^+ u_emu^-bar{ u}_mu b bar{b}j$ at NLO QCD accuracy, which describes $tbar{t}j$ production with leptonic decays beyond the Narrow Width Approximation (NWA), and discuss the impact of the off-shell effects through comparisons with NWA. Finally we explore the sensitivity of $tbar{t}j$ in the context of top-quark mass extraction with the template method, considering two benchmark observables as case studies.
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.
In the framework of the large extra dimensions (LED) model, the effects of LED on the processes rrtth and eetth at future linear colliders are investigated in both polarized and unpolarized collision modes. The results show that the virtual Kaluza-Klein (KK) graviton exchange can significantly modify the standard model expectations for these processes with certain polarizations of initial states. The process rrtth with $sqrt{s}=3.5 TeV$ allows the effective scale $Lambda_T$ to be probed up to 7.8 and 8.6 TeV in the unpolarized and $P_{gamma} = 0.9$, J=2 polarized $gamma gamma$ collision modes, respectively. For the eetth process with $sqrt{s}=3.5 TeV$, the upper limits of $Lambda_T$ to be observed can be 6.7 and 7.0 TeV in the unpolarized and $P_{e^+} = 0.6$, $P_{e^-} = 0.8$, $-+$ polarized $e^+e^-$ collision modes, respectively. We find the rrtth channel in J=2 polarized photon collision mode provides a possibility to improve the sensitivity to the graviton tower exchange.
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.
Bounds on invisible decays of the Higgs boson from $tbar{t}H$ production were inferred from a CMS search for stop quarks decaying to $tbar{t}$ and missing transverse momentum. Limits on the production of $tbar{t}H$ relied on the efficiency of the CMS selection for $tbar{t}H$, as measured in a simulated sample. An error in the generation of the simulated sample lead to a significant overestimate of the selection efficiency. Corrected results are presented.
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